This Letter presents results from a combination of searches for Higgs boson pair production using 126$-$140 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV recorded with the ATLAS detector. At 95% confidence level (CL), the upper limit on the production rate is 2.9 times the standard model (SM) prediction, with an expected limit of 2.4 assuming no Higgs boson pair production. Constraints on the Higgs boson self-coupling modifier $\kappa_{\lambda}=\lambda_{HHH}/\lambda_{HHH}^\mathrm{SM}$, and the quartic $HHVV$ coupling modifier $\kappa_{2V}=g_{HHVV}/g_{HHVV}^\mathrm{SM}$, are derived individually, fixing the other parameter to its SM value. The observed 95% CL intervals are $-1.2 < \kappa_{\lambda} < 7.2$ and $0.6 < \kappa_{2V} < 1.5$, respectively, while the expected intervals are $-1.6 < \kappa_{\lambda} < 7.2$ and $0.4 < \kappa_{2V} < 1.6$ in the SM case. Constraints obtained for several interaction parameters within Higgs effective field theory are the strongest to date, offering insights into potential deviations from SM predictions.
Observed and expected 95% CL upper limits on the signal strength for inclusive ggF HH and VBF HH production from the bb̄τ<sup>+</sup>τ<sup>-</sup>, bb̄γγ, bb̄bb̄, multilepton and bb̄ℓℓ+E<sub>T</sub><sup>miss</sup> decay channels, and their statistical combination. The predicted SM cross-section assumes m<sub>H</sub> = 125 GeV. The expected limit, along with its associated ±1σ and ±2σ bands, is calculated for the assumption of no HH production and with all NPs profiled to the observed data.
Expected value of the test statistic (-2ln$\Lambda$), as a function of the $\kappa_\lambda$ parameter for $b\bar{b}b\bar{b}$.
Expected value of the test statistic (-2ln$\Lambda$), as a function of the $\kappa_\lambda$ parameter for $b\bar{b}\tau\tau$.
A search is presented for flavour-changing neutral-current interactions involving the top quark, the Higgs boson and an up-type quark ($q=u,c$) with the ATLAS detector at the Large Hadron Collider. The analysis considers leptonic decays of the top quark along with Higgs boson decays into two $W$ bosons, two $Z$ bosons or a $\tau^{+}\tau^{-}$ pair. It focuses on final states containing either two leptons (electrons or muons) of the same charge or three leptons. The considered processes are $t\bar{t}$ and $Ht$ production. For the $t\bar{t}$ production, one top quark decays via $t\to Hq$. The proton-proton collision data set analysed amounts to 140 fb$^{-1}$ at $\sqrt{s}=13$ TeV. No significant excess beyond Standard Model expectations is observed and upper limits are set on the $t\to Hq$ branching ratios at 95% confidence level, amounting to observed (expected) limits of $\mathcal{B}(t\to Hu)<2.8\,(3.0) \times 10^{-4}$ and $\mathcal{B}(t\to Hc)<3.3\,(3.8) \times 10^{-4}$. Combining this search with other searches for $tHq$ flavour-changing neutral-current interactions previously conducted by ATLAS, considering $H\to b\bar{b}$ and $H\to\gamma\gamma$ decays, as well as $H\to\tau^{+}\tau^{-}$ decays with one or two hadronically decaying $\tau$-leptons, yields observed (expected) upper limits on the branching ratios of $\mathcal{B}(t\to Hu)<2.6\,(1.8) \times 10^{-4}$ and $\mathcal{B}(t\to Hc)<3.4\,(2.3) \times 10^{-4}$.
Pre-fit background composition of the SR$2\ell$ Dec. The table shows the event yields as opposed to just the percentages of the relevant background processes.
Pre-fit background composition of the SR$2\ell$ Prod. The table shows the event yields as opposed to just the percentages of the relevant background processes.
Pre-fit background composition of the SR$3\ell$ Dec. The table shows the event yields as opposed to just the percentages of the relevant background processes.
Measurements of inclusive, differential cross-sections for the production of events with missing transverse momentum in association with jets in proton-proton collisions at $\sqrt{s}=13~$TeV are presented. The measurements are made with the ATLAS detector using an integrated luminosity of $140~$fb$^{-1}$ and include measurements of dijet distributions in a region in which vector-boson fusion processes are enhanced. They are unfolded to correct for detector resolution and efficiency within the fiducial acceptance, and are designed to allow robust comparisons with a wide range of theoretical predictions. A measurement of differential cross sections for the $Z~\to \nu\nu$ process is made. The measurements are generally well-described by Standard Model predictions except for the dijet invariant mass distribution. Auxiliary measurements of the hadronic system recoiling against isolated leptons, and photons, are also made in the same phase space. Ratios between the measured distributions are then derived, to take advantage of cancellations in modelling effects and some of the major systematic uncertainties. These measurements are sensitive to new phenomena, and provide a mechanism to easily set constraints on phenomenological models. To illustrate the robustness of the approach, these ratios are compared with two common Dark Matter models, where the constraints derived from the measurement are comparable to those set by dedicated detector-level searches.
The measured $p_\text{T}^\text{miss}$ differential cross-sections in the $p_\text{T}^\text{miss}+\text{jets}$ region of the incluse jet phase space, compared with the SM predictions. The middle panels show the ratios of the predictions to the data, along with their uncertainties, while the lower panels show the relative contributions from different SM processes relative to the total MEPS@NLO prediction. Note that individually numbered PDF components ('dK_PDF_') in the uncertainty breakdown correspond to NNPDF Hessian eigenvectors. Uncertainty components labeled 'VV_dK' include Vjj processes.
The measured $p_\text{T}^\text{recoil}$ differential cross-sections in the $1\mu+\text{jets}$ region of the incluse jet phase space, compared with the SM predictions. The middle panels show the ratios of the predictions to the data, along with their uncertainties, while the lower panels show the relative contributions from different SM processes relative to the total MEPS@NLO prediction. Note that individually numbered PDF components ('dK_PDF_') in the uncertainty breakdown correspond to NNPDF Hessian eigenvectors. Uncertainty components labeled 'VV_dK' include Vjj processes.
The measured $p_\text{T}^\text{recoil}$ differential cross-sections in the $1e+\text{jets}$ region of the incluse jet phase space, compared with the SM predictions. The middle panels show the ratios of the predictions to the data, along with their uncertainties, while the lower panels show the relative contributions from different SM processes relative to the total MEPS@NLO prediction. Note that individually numbered PDF components ('dK_PDF_') in the uncertainty breakdown correspond to NNPDF Hessian eigenvectors. Uncertainty components labeled 'VV_dK' include Vjj processes.
The production of single top quarks and top antiquarks via the $t$-channel exchange of a virtual $W$ boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the LHC using $140\,\mathrm{fb^{-1}}$ of ATLAS data. The total cross-sections are determined to be $\sigma(tq)=137^{+8}_{-8}\,\mathrm{pb}$ and $\sigma(\bar{t}q)=84^{+6}_{-5}\,\mathrm{pb}$ for top-quark and top-antiquark production, respectively. The combined cross-section is found to be $\sigma(tq+\bar{t}q)=221^{+13}_{-13}\,\mathrm{pb}$ and the cross-section ratio is $R_{t}=\sigma(tq)/\sigma(\bar{t}q)=1.636^{+0.036}_{-0.034}$. The predictions at next-to-next-to-leading-order in quantum chromodynamics are in good agreement with these measurements. The predicted value of $R_{t}$ using different sets of parton distribution functions is compared with the measured value, demonstrating the potential to further constrain the functions when using this result in global fits. The measured cross-sections are interpreted in an effective field theory approach, setting limits at the 95% confidence level on the strength of a four-quark operator and an operator coupling the third quark generation to the Higgs boson doublet: $-0.37 < C_{Qq}^{3,1}/\Lambda^2 < 0.06$ and $-0.87 < C_{\phi Q}^{3}/\Lambda^2 < 1.42$. The constraint $|V_{tb}|>0.95$ at the 95% confidence level is derived from the measured value of $\sigma(tq+\bar{t}q)$. In a more general approach, pairs of CKM matrix elements involving top quarks are simultaneously constrained, leading to confidence contours in the corresponding two-dimensional parameter spaces.
The 17 variables used for the training of the NN ordered by their discriminating power. The jet that is not \(b\)-tagged is referred to as the untagged jet. The charged lepton is denoted \(\ell\). The sphericity tensor \(S^{\alpha\beta}\) used to define the sphericity \(S\) is formed with the three-momenta \(\vec{p}_i\) of the reconstructed objects, namely the jets, the charged lepton and the reconstructed neutrino. The tensor is given by \(S^{\alpha\beta}=\frac{\sum_i p_i^\alpha p_i^\beta}{\sum_i |\vec{p}_i|^2}\) where \(\alpha\) and \(\beta\) correspond to the spatial components $x$, $y$ and $z$.
The impact of different groups of systematic uncertainties on the \(\sigma(tq)\) , \(\sigma(\bar t q)\), \(\sigma(tq + \bar t q)\) and \(R_t\), given in %.
The impact of the eight most important systematic uncertainties on the \(\sigma(tq)\) , \(\sigma(\bar t q)\) and \(\sigma(tq + \bar t q)\), given in %. The sequence of the uncertainties is given by the impact on \(\sigma(tq + \bar t q)\)
This Letter presents the first study of the energy-dependence of diboson polarization fractions in $WZ \rightarrow \ell\nu \ell'\ell'~(\ell, \ell'=e, \mu)$ production. The data set used corresponds to an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the ATLAS detector. Two fiducial regions with an enhanced presence of events featuring two longitudinally-polarized bosons are defined. A non-zero fraction of events with two longitudinally-polarized bosons is measured with an observed significance of 5.3 standard deviations in the region with $100<p_T^Z\leq200$ GeV and 1.6 standard deviations in the region with $p_T^Z>200$ GeV, where $p_T^Z$ is the transverse momentum of the $Z$ boson. This Letter also reports the first study of the Radiation Amplitude Zero effect. Events with two transversely-polarized bosons are analyzed for the $\Delta Y(\ell_W Z)$ and $\Delta Y(WZ)$ distributions defined respectively as the rapidity difference between the lepton from the $W$ boson decay and the $Z$ boson and the rapidity difference between the $W$ boson and the $Z$ boson. Significant suppression of events near zero is observed in both distributions. Unfolded $\Delta Y(\ell_W Z)$ and $\Delta Y(WZ)$ distributions are also measured and compared to theoretical predictions.
Polarization fractions in the region with $100<p_T^Z\leq200$ GeV using three unconstrained parameters.
Polarization fractions in the region with $p_T^Z>200$ GeV using three unconstrained parameters.
Fraction of events where both bosons are longitudinally polarized in the region with $100<p_T^Z\leq200$ GeV using two unconstrained parameters.
This paper presents a search for top-squark pair production in final states with a top quark, a charm quark and missing transverse momentum. The data were collected with the ATLAS detector during LHC Run 2 and corresponds to an integrated luminosity of 139fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV. The analysis is motivated by an extended Minimal Supersymmetric Standard Model featuring a non-minimal flavour violation in the second- and third-generation squark sector. The top squark in this model has two possible decay modes, either $\tilde{t}_1 \rightarrow c\tilde{\chi}_1^0$ or $\tilde{t}_1\rightarrow t\tilde{\chi}_1^0$, where the $\tilde{\chi}_1^0$ is undetected. The analysis is optimised assuming that both of the decay modes are equally probable, leading to the most likely final state of $tc + E_{\text{T}}^{\text{miss}}$. Good agreement is found between the Standard Model expectation and the data in the search regions. Exclusion limits at 95% CL are obtained in the $m(\tilde{t}_1)$ vs $m(\tilde{\chi}_1^0)$ plane and, in addition, limits on the branching ratio of the $\tilde{t}_1\rightarrow t\tilde{\chi}_1^0$ decay as a function of $m(\tilde{t}_1)$ are also produced. Top-squark masses of up to 800 GeV are excluded for scenarios with light neutralinos, and top-squark masses up to 600 GeV are excluded in scenarios where the neutralino and the top squark are almost mass degenerate.
<b>- - - - - - - - Overview of HEPData Record - - - - - - - -</b> <br><br> <b>Exclusion contours:</b> <ul> <li><a href="?table=mass_obs">Observed exclusion contour in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$</a> <li><a href="?table=mass_exp">Expected exclusion contour in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$</a> <li><a href="?table=mass_band_1">$\pm1\sigma$ exclusion contour in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$</a> <li><a href="?table=mass_band_2">$\pm1\sigma$ exclusion contour in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$</a> <li><a href="?table=br_m1_obs">Observed exclusion contour in the $m_{\tilde{t}_1} - $BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1)$ plane, assuming $m_{\tilde\chi^0_1} = 1 \mathrm{GeV}$</a> <li><a href="?table=br_m1_exp">Expected exclusion contour in the $m_{\tilde{t}_1} - $BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1)$ plane, assuming $m_{\tilde\chi^0_1} = 1 \mathrm{GeV}$</a> <li><a href="?table=br_m1_band_1">$\pm1\sigma$ exclusion contour in the $m_{\tilde{t}_1} - $BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1)$ plane, assuming $m_{\tilde\chi^0_1} = 1 \mathrm{GeV}$</a> <li><a href="?table=br_m1_band_2">$\pm1\sigma$ exclusion contour in the $m_{\tilde{t}_1} - $BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1)$ plane, assuming $m_{\tilde\chi^0_1} = 1 \mathrm{GeV}$</a> </ul> <b>Upper limits:</b> <ul> <li><a href="?table=mass_upperLimits_obs">Observed upper limits on the top-spartner pair production cross-section at the 95% CL in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$</a> <li><a href="?table=br_m1_upperLimits_obs">Observed upper limits on the top-spartner pair production cross-section at the 95% CL in the $m_{\tilde{t}_1} - $BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1)$ plane, assuming $m_{\tilde\chi^0_1} = 1 \mathrm{GeV}$.</a> <li><a href="?table=mass_upperLimits_exp">Expected upper limits on the top-spartner pair production cross-section at the 95% CL in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$</a> <li><a href="?table=br_m1_upperLimits_exp">Expected upper limits on the top-spartner pair production cross-section at the 95% CL in the $m_{\tilde{t}_1} - $BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1)$ plane, assuming $m_{\tilde\chi^0_1} = 1 \mathrm{GeV}$.</a> </ul> <b>Kinematic distributions:</b> <ul> <li><a href="?table=SRA_ntop">SRA region number of top-tagged jets distribution</a> <li><a href="?table=SRA_mttwo">SRA region $m_{\mathrm{T2}}(j^{b}_{R=1.0}, c)$ distribution</a> <li><a href="?table=SRB_ptc">SRB region leading c-tagged jet $p_{\mathrm{T}}$</a> <li><a href="?table=SRB_mtj">SRB region $m_{\mathrm{T}}(j, E_{\mathrm{T}}^{\mathrm{miss}})_{\mathrm{close}}$ distribution</a> <li><a href="?table=SRC_metsig">SRC region missing transverse momentum significance distribution</a> <li><a href="?table=SRC_mtj">SRC region $m_{\mathrm{T}}(j, E_{\mathrm{T}}^{\mathrm{miss}})_{\mathrm{close}}$ distribution</a> <li><a href="?table=SRD_NN">SRD NN signal score distribution</a> <li><a href="?table=SRD_meff">SRD $m_{\mathrm{eff}}$ distribution</a> </ul> <b>Pull distributions:</b> <ul> <li><a href="?table=SRABCPull">Pull plots showing the SRA, SRB and SRC post-fit data and SM agreement using the background-only fit configuration</a> <li><a href="?table=SRDPull">Pull plots showing the SRD post-fit data and SM agreement using the background-only fit configuration</a> </ul> <b>Cut flows:</b> <ul> <li><a href="?table=cutflow_SRA">Cutflow of 3 signal points in the SRA region.</a> <li><a href="?table=cutflow_SRB">Cutflow of 3 signal points in the SRB region.</a> <li><a href="?table=cutflow_SRC">Cutflow of 3 signal points in the SRC region.</a> <li><a href="?table=cutflow_SRD750">Cutflow of 3 signal points in the SRD750 region.</a> <li><a href="?table=cutflow_SRD1000">Cutflow of 3 signal points in the SRD1000 region.</a> <li><a href="?table=cutflow_SRD1250">Cutflow of 3 signal points in the SRD1250 region.</a> <li><a href="?table=cutflow_SRD1500">Cutflow of 3 signal points in the SRD1500 region.</a> <li><a href="?table=cutflow_SRD1750">Cutflow of 3 signal points in the SRD1750 region.</a> <li><a href="?table=cutflow_SRD2000">Cutflow of 3 signal points in the SRD2000 region.</a> </ul> <b>Acceptance and efficiencies:</b> <ul> <li> <b>SRA_bin1:</b> <a href="?table=Acc_SRA_bin1">Acceptance table of the SRA$^{[450,575]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRA_bin1">Efficiency table of the SRA$^{[450,575]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRA_bin2:</b> <a href="?table=Acc_SRA_bin2">Acceptance table of the SRA$^{\geq 575}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRA_bin2">Efficiency table of the SRA$^{\geq 575}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRB_bin1:</b> <a href="?table=Acc_SRB_bin1">Acceptance table of the SRB$^{[100,150]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRB_bin1">Efficiency table of the SRB$^{[100,150]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRB_bin2:</b> <a href="?table=Acc_SRB_bin2">Acceptance table of the SRB$^{[150,400]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRB_bin2">Efficiency table of the SRB$^{[150,400]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRB_bin3:</b> <a href="?table=Acc_SRB_bin3">Acceptance table of the SRB$^{\geq 400}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRB_bin3">Efficiency table of the SRB$^{\geq 400}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRC_bin1:</b> <a href="?table=Acc_SRC_bin1">Acceptance table of the SRC$^{[100,150]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRC_bin1">Efficiency table of the SRC$^{[100,150]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRC_bin2:</b> <a href="?table=Acc_SRC_bin2">Acceptance table of the SRC$^{[150,300]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRC_bin2">Efficiency table of the SRC$^{[150,300]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRC_bin3:</b> <a href="?table=Acc_SRC_bin3">Acceptance table of the SRC$^{[300,500]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRC_bin3">Efficiency table of the SRC$^{[300,500]}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRC_bin4:</b> <a href="?table=Acc_SRC_bin4">Acceptance table of the SRC$^{\geq 500}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRC_bin4">Efficiency table of the SRC$^{\geq 500}$ in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRD_bin1:</b> <a href="?table=Acc_SRD_bin1">Acceptance table of the SRD750 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRD_bin1">Efficiency table of the SRD750 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRD_bin2:</b> <a href="?table=Acc_SRD_bin2">Acceptance table of the SRD1000 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRD_bin2">Efficiency table of the SRD1000 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRD_bin3:</b> <a href="?table=Acc_SRD_bin3">Acceptance table of the SRD1250 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRD_bin3">Efficiency table of the SRD1250 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRD_bin4:</b> <a href="?table=Acc_SRD_bin4">Acceptance table of the SRD1500 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRD_bin4">Efficiency table of the SRD1500 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRD_bin5:</b> <a href="?table=Acc_SRD_bin5">Acceptance table of the SRD1750 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRD_bin5">Efficiency table of the SRD1750 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <li> <b>SRD_bin6:</b> <a href="?table=Acc_SRD_bin6">Acceptance table of the SRD2000 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> <a href="?table=Eff_SRD_bin6">Efficiency table of the SRD2000 in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.</a> </ul> <b>Truth Code snippets</b> are available under "Resources" (purple button on the left)
Observed exclusion limits at the 95% CL in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$.
Observed exclusion limits at the 95% CL in the $\tilde{t}_1 - \tilde\chi^0_1$ mass plane, assuming BR$(\tilde{t}_1 \rightarrow t + \tilde\chi^0_1) = 0.5$ and a $+1 \sigma$ deviation of the NNLO+NNLL theoretical cross-section of a $\tilde{t}_1$ pair-production.
A combination of fifteen top quark mass measurements performed by the ATLAS and CMS experiments at the LHC is presented. The data sets used correspond to an integrated luminosity of up to 5 and 20$^{-1}$ of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, respectively. The combination includes measurements in top quark pair events that exploit both the semileptonic and hadronic decays of the top quark, and a measurement using events enriched in single top quark production via the electroweak $t$-channel. The combination accounts for the correlations between measurements and achieves an improvement in the total uncertainty of 31% relative to the most precise input measurement. The result is $m_\mathrm{t}$ = 172.52 $\pm$ 0.14 (stat) $\pm$ 0.30 (syst) GeV, with a total uncertainty of 0.33 GeV.
Uncertainties on the $m_{t}$ values extracted in the LHC, ATLAS, and CMS combinations arising from the categories described in the text, sorted in order of decreasing value of the combined LHC uncertainty.
Statistical combinations of searches for charginos and neutralinos using various decay channels are performed using $139\,$fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13\,$TeV with the ATLAS detector at the Large Hadron Collider. Searches targeting pure-wino chargino pair production, pure-wino chargino-neutralino production, or higgsino production decaying via Standard Model $W$, $Z$, or $h$ bosons are combined to extend the mass reach to the produced SUSY particles by 30-100 GeV. The depth of the sensitivity of the original searches is also improved by the combinations, lowering the 95% CL cross-section upper limits by 15%-40%.
Expected 95% CL exclusion limits on the simplified models of chargino-pair production decaying via W bosons.
$+1\sigma$ expected 95% CL exclusion limits on the simplified models of chargino-pair production decaying via W bosons.
$-1\sigma$ expected 95% CL exclusion limits on the simplified models of chargino-pair production decaying via W bosons.
A summary of the constraints from searches performed by the ATLAS Collaboration for the electroweak production of charginos and neutralinos is presented. Results from eight separate ATLAS searches are considered, each using 140 fb$^{-1}$ of proton-proton data at a centre-of-mass energy of $\sqrt{s}$=13 TeV collected at the Large Hadron Collider during its second data-taking run. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, where R-parity conservation is assumed and the lightest supersymmetric particle is assumed to be the lightest neutralino. Constraints from previous electroweak, flavour and dark matter related measurements are also considered. The results are presented in terms of constraints on supersymmetric particle masses and are compared with limits from simplified models. Also shown is the impact of ATLAS searches on parameters such as the dark matter relic density and the spin-dependent and spin-independent scattering cross-sections targeted by direct dark matter detection experiments. The Higgs boson and Z boson `funnel regions', where a low-mass neutralino would not oversaturate the dark matter relic abundance, are almost completely excluded by the considered constraints. Example spectra for non-excluded supersymmetric models with light charginos and neutralinos are also presented.
SLHA files and exclusion information (in CSV format) are available to download for the pMSSM models in this paper. Please refer to <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2020-15/inputs/ATLAS_EW_pMSSM_Run2.html">this web page</a> for download links along with a description of the contents.
SLHA files and exclusion information (in CSV format) are available to download for the pMSSM models in this paper. Please refer to <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2020-15/inputs/ATLAS_EW_pMSSM_Run2.html">this web page</a> for download links along with a description of the contents.
This paper presents a search for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly massless gravitino. The search targets events where each Higgs boson decays into $b\bar{b}$, leading to a reconstructed final state with at least three energetic $b$-jets and This paper presents a search for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly massless gravitino. The search targets events where each Higgs boson decays into $b\bar{b}$, leading to a reconstructed final state with at least three energetic $b$-jets and missing transverse momentum. Two complementary analysis channels are used, with each channel specifically targeting either low or high values of the higgsino mass. The low-mass (high-mass) channel exploits 126 (139) fb$^{-1}$ of $\sqrt{s}=13$ TeV data collected by the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess above the Standard Model prediction is found. At 95% confidence level, masses between 130 GeV and 940 GeV are excluded for higgsinos decaying exclusively into Higgs bosons and gravitinos. Exclusion limits as a function of the higgsino decay branching ratio to a Higgs boson are also reported.
Post-fit SR yields of the high-mass channel. The upper panel shows the observed number of events, as well the post-fit background predictions in each region. The bottom panel shows the ratio of the observed data and the total background prediction. The shaded areas correspond to the total statistical and systematic uncertainties obtained after the fit and described in Section 6.
Post-fit SR yields of the high-mass channel. The upper panel shows the observed number of events, as well the post-fit background predictions in each region. The bottom panel shows the ratio of the observed data and the total background prediction. The shaded areas correspond to the total statistical and systematic uncertainties obtained after the fit and described in Section 6.
Post-fit SR yields of the high-mass channel. The upper panel shows the observed number of events, as well the post-fit background predictions in each region. The bottom panel shows the ratio of the observed data and the total background prediction. The shaded areas correspond to the total statistical and systematic uncertainties obtained after the fit and described in Section 6.
Higgsinos with masses near the electroweak scale can solve the hierarchy problem and provide a dark matter candidate, while detecting them at the LHC remains challenging if their mass splitting is $\mathcal{O}(1 \text{GeV})$. This Letter presents a novel search for nearly mass-degenerate Higgsinos in events with an energetic jet, missing transverse momentum, and a low-momentum track with a significant transverse impact parameter using 140 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV collected by the ATLAS experiment. For the first time since LEP, a range of mass splittings between the lightest charged and neutral Higgsinos from $0.3$ GeV to $0.9$ GeV is excluded at 95$\%$ confidence level, with a maximum reach of approximately $170$ GeV in the Higgsino mass.
Number of expected and observed data events in the SR (top), and the model-independent upper limits obtained from their consistency (bottom). The symbol $\tau_{\ell}$ ($\tau_{h}$) refers to fully-leptonic (hadron-involved) tau decays. The Others category includes contributions from minor background processes including $t\bar{t}$, single-top and diboson. The individual uncertainties can be correlated and do not necessarily sum up in quadrature to the total uncertainty. The bottom section shows the observed 95% CL upper limits on the visible cross-section ($\langle\epsilon\sigma\rangle_{\mathrm{obs}}^{95}$), on the number of generic signal events ($S_{\mathrm{obs}}^{95}$) as well as the expected limit ($S_{\mathrm{exp}}^{95}$) given the expected number (and $\pm 1\sigma$ deviations from the expectation) of background events.
Number of expected and observed data events in the SR (top), and the model-independent upper limits obtained from their consistency (bottom). The symbol $\tau_{\ell}$ ($\tau_{h}$) refers to fully-leptonic (hadron-involved) tau decays. The Others category includes contributions from minor background processes including $t\bar{t}$, single-top and diboson. The individual uncertainties can be correlated and do not necessarily sum up in quadrature to the total uncertainty. The bottom section shows the observed 95% CL upper limits on the visible cross-section ($\langle\epsilon\sigma\rangle_{\mathrm{obs}}^{95}$), on the number of generic signal events ($S_{\mathrm{obs}}^{95}$) as well as the expected limit ($S_{\mathrm{exp}}^{95}$) given the expected number (and $\pm 1\sigma$ deviations from the expectation) of background events.
Expected (dashed black line) and observed (solid red line) 95% CL exclusion limits on the higgsino simplified model being considered. These are shown with $\pm 1\sigma_{\mathrm{exp}}$ (yellow band) from experimental systematic and statistical uncertainties, and with $\pm 1\sigma_{\mathrm{theory}}^{\mathrm{SUSY}}$ (red dotted lines) from signal cross-section uncertainties, respectively. The limits set by the latest ATLAS searches using the soft lepton and disappearing track signatures are illustrated by the blue and green regions, respectively, while the limit imposed by the LEP experiments is shown in gray. The dot-dashed gray line indicates the predicted mass-splitting for the pure higgsino scenario.
This Letter presents the first study of Higgs boson production in association with a vector boson (V = W or Z) in the fully hadronic $qqbb$ final state using data recorded by the ATLAS detector at the LHC in proton-proton collisions at $\sqrt{s}=13$ TeV and corresponding to an integrated luminosity of 137 fb$^{-1}$. The vector bosons and Higgs bosons are each reconstructed as large-radius jets and tagged using jet substructure techniques. Dedicated tagging algorithms exploiting $b$-tagging properties are used to identify jets consistent with Higgs bosons decaying into $b\bar{b}$. Dominant backgrounds from multijet production are determined directly from the data, and a likelihood fit to the jet mass distribution of Higgs boson candidates is used to extract the number of signal events. The VH production cross section is measured inclusively and differentially in several ranges of Higgs boson transverse momentum: 250-450, 450-650, and greater than 650 GeV. The inclusive signal yield relative to the standard model expectation is observed to be $\mu = 1.4 ^{+1.0}_{-0.9}$ and the corresponding cross section is $3.1 \pm 1.3\, (stat.)\: ^{+1.8}_{-1.4}\, (syst.$) pb.
Higgs candidate jet mass distributions in the signal region for $p_{T,J}^H$ in [250,450) GeV obtained after the inclusive fit with a single Z+jets normalization factor and a single signal strength.
Higgs candidate jet mass distributions in the signal region for $p_{T,J}^H$ in [450,650) GeV obtained after the inclusive fit with a single Z+jets normalization factor and a single signal strength.
Higgs candidate jet mass distributions in the signal region for $p_{T,J}^H \geq 650$ GeV obtained after the inclusive fit with a single Z+jets normalization factor and a single signal strength.
Measurements of both the inclusive and differential production cross sections of a top-quark-top-antiquark pair in association with a $Z$ boson ($t\bar{t}Z$) are presented. Final states with two, three or four isolated leptons (electrons or muons) are targeted. The measurements use the data recorded by the ATLAS detector in $pp$ collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider during the years 2015-2018, corresponding to an integrated luminosity of $140$ fb$^{-1}$. The inclusive cross section is measured to be $\sigma_{t\bar{t}Z}= 0.86 \pm 0.04~\mathrm{(stat.)} \pm 0.04~\mathrm{(syst.)}~$pb and found to be in agreement with the most advanced Standard Model predictions. The differential measurements are presented as a function of a number of observables that probe the kinematics of the $t\bar{t}Z$ system. Both the absolute and normalised differential cross-section measurements are performed at particle level and parton level for specific fiducial volumes, and are compared with NLO+NNLL theoretical predictions. The results are interpreted in the framework of Standard Model effective field theory and used to set limits on a large number of dimension-6 operators involving the top quark. The first measurement of spin correlations in $t\bar{t}Z$ events is presented: the results are in agreement with the Standard Model expectations, and the null hypothesis of no spin correlations is disfavoured with a significance of $1.8$ standard deviations.
All the entries of this HEP data record are listed. Figure and Table numbers are the same as in the paper.
Definition of the dilepton signal regions.
Definition of the trilepton signal regions.
This paper presents the measurement of fiducial and differential cross sections for both the inclusive and electroweak production of a same-sign $W$-boson pair in association with two jets ($W^\pm W^\pm jj$) using 139 fb$^{-1}$ of proton-proton collision data recorded at a centre-of-mass energy of $\sqrt{s}=13$ TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed by selecting two same-charge leptons, electron or muon, and at least two jets with large invariant mass and a large rapidity difference. The measured fiducial cross sections for electroweak and inclusive $W^\pm W^\pm jj$ production are $2.92 \pm 0.22\, \text{(stat.)} \pm 0.19\, \text{(syst.)}$ fb and $3.38 \pm 0.22\, \text{(stat.)} \pm 0.19\, \text{(syst.)}$ fb, respectively, in agreement with Standard Model predictions. The measurements are used to constrain anomalous quartic gauge couplings by extracting 95% confidence level intervals on dimension-8 operators. A search for doubly charged Higgs bosons $H^{\pm\pm}$ that are produced in vector-boson fusion processes and decay into a same-sign $W$ boson pair is performed. The largest deviation from the Standard Model occurs for an $H^{\pm\pm}$ mass near 450 GeV, with a global significance of 2.5 standard deviations.
Fiducial differential cross section of the electroweak $W^\pm W^\pm jj$ production as a function of $m_{\ell\ell}$. The correlation of uncertainties of the measured cross section across bins is presented in Table 11.
Fiducial differential cross section of the electroweak $W^\pm W^\pm jj$ production as a function of $m_{\mathrm{T}}$. The correlation of uncertainties of the measured cross section across bins is presented in Table 12.
Fiducial differential cross section of the electroweak $W^\pm W^\pm jj$ production as a function of $m_{\mathrm{jj}}$. The correlation of uncertainties of the measured cross section across bins is presented in Table 13.
A search is reported for long-lived dark photons with masses between 0.1 GeV and 15 GeV, from exotic decays of Higgs bosons produced via vector-boson-fusion. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are probed. This search uses the full LHC Run 2 (2015-2018) data sample collected in proton-proton collisions at $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of 139 $fb^{-1}$. Dominant backgrounds from Standard Model processes and non-collision sources are estimated by using data-driven techniques. The observed event yields in the signal regions are consistent with the expected background. Upper limits on the Higgs boson to dark photon branching fraction are reported as a function of the dark-photon mean proper decay length or of the dark-photon mass and the coupling between the Standard Model and the potential dark sector. This search is combined with previous ATLAS searches obtained in the gluon-gluon fusion and \textit{WH} production modes. A branching fraction above 10% is excluded at 95% CL for a 125 GeV Higgs boson decaying into two dark photons for dark-photon mean proper decay lengths between 173 and 1296 mm and mass of 10 GeV.
Observed 95% CL upper limits on B(H→ 2γ<sub>d</sub>+X) for different γ<sub>d</sub> masses and a 125 GeV Higgs boson, as a function of the dark-photon mean proper decay length cτ. The limits are shown for the SR<sub>μ</sub> search channel, assuming an FRVZ signal model. The hatched band denotes the region in which the branching ratio is larger than unity.
Observed 95% CL upper limits on B(H→ 2γ<sub>d</sub>+X) for different γ<sub>d</sub> masses and a 125 GeV Higgs boson, as a function of the dark-photon mean proper decay length cτ. The limits are shown for the SR<sub>c</sub><sup>L</sup> search channel, assuming an FRVZ signal model. The hatched band denotes the region in which the branching ratio is larger than unity.
Observed 95% CL upper limits on B(H→ 2γ<sub>d</sub>+X) for different γ<sub>d</sub> masses and a 125 GeV Higgs boson, as a function of the dark-photon mean proper decay length cτ. The limits are shown for the SR<sub>c</sub><sup>H</sup> search channel, assuming an FRVZ signal model. The hatched band denotes the region in which the branching ratio is larger than unity.
A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to 139 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: $b\bar{b}b\bar{b}$, $b\bar{b}\tau^+\tau^-$ and $b\bar{b}\gamma\gamma$. No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV-5 TeV. The observed (expected) limits are in the range 0.96-600 fb (1.2-390 fb). The limits are interpreted in the Type-I Two-Higgs-Doublet Model and the Minimimal Supersymmetric Standard Model, and constrain parameter space not previously excluded by other searches.
Local p-value as a function of the resonance mass $m_{X}$. Some table entries are empty because resonance masses from 251 GeV to 5 TeV are considered, whereas some channels only use masses in a certain, more restricted, range.
Observed significance as a function of the resonance $m_{X}$. Some table entries are empty because resonance masses from 251 GeV to 5 TeV are considered, whereas some channels only use masses in a certain, more restricted, range.
Observed and expected upper limits at the 95% CL on the resonant Higgs boson pair production cross section as a function of the resonance mass $m_{X}$. Some table entries are empty because resonance masses from 251 GeV to 5 TeV are considered, whereas some channels only use masses in a certain, more restricted, range.
This paper presents a search for a new $Z^\prime$ resonance decaying into a pair of dark quarks which hadronise into dark hadrons before promptly decaying back as Standard Model particles. This analysis is based on proton-proton collision data recorded at $\sqrt{s}=13$ TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. After selecting events containing large-radius jets with high track multiplicity, the invariant mass distribution of the two highest-transverse-momentum jets is scanned to look for an excess above a data-driven estimate of the Standard Model multijet background. No significant excess of events is observed and the results are thus used to set 95 % confidence-level upper limits on the production cross-section times branching ratio of the $Z^\prime$ to dark quarks as a function of the $Z^\prime$ mass for various dark-quark scenarios.
Distribution of the di-jet invariant mass, $m_{\mathrm{JJ}}$ for the data, the simulated multi-jet background and of some representative signals (models A, B, C and D with $m_{Z'}=2.5$ TeV), shown after applying the preselections described in the text. The simulated background is normalised to the data and the signals are normalised to a production cross-section of 10 fb.
Distributions of the number of tracks associated to the leading jet, $n_{track,1}$, for the data, the simulated multi-jet background and of some representative signals (models A, B, C and D with $m_{Z^\prime}=2.5$ TeV), shown after applying the preselections described in the text. All distributions are normalised to unity. The uncertainty band around the background prediction corresponds to the modelling uncertainty described in Section 6.
Distributions of the number of tracks associated to the subleading jet, $n_{track,2}$, for the data, the simulated multi-jet background and of some representative signals (models A, B, C and D with $m_{Z^\prime}=2.5$ TeV), shown after applying the preselections described in the text. All distributions are normalised to unity. The uncertainty band around the background prediction corresponds to the modelling uncertainty described in Section 6.
A search for a heavy CP-odd Higgs boson, $A$, decaying into a $Z$ boson and a heavy CP-even Higgs boson, $H$, is presented. It uses the full LHC Run 2 dataset of $pp$ collisions at $\sqrt{s}=13$ TeV collected with the ATLAS detector, corresponding to an integrated luminosity of $140$ fb$^{-1}$. The search for $A\to ZH$ is performed in the $\ell^+\ell^- t\bar{t}$ and $\nu\bar{\nu}b\bar{b}$ final states and surpasses the reach of previous searches in different final states in the region with $m_H>350$ GeV and $m_A>800$ GeV. No significant deviation from the Standard Model expectation is found. Upper limits are placed on the production cross-section times the decay branching ratios. Limits with less model dependence are also presented as functions of the reconstructed $m(t\bar{t})$ and $m(b\bar{b})$ distributions in the $\ell^+\ell^- t\bar{t}$ and $\nu\bar{\nu}b\bar{b}$ channels, respectively. In addition, the results are interpreted in the context of two-Higgs-doublet models.
<b><u>Overview of HEPData Record</u></b><br> <b>Upper limits on cross-sections:</b> <ul> <li><a href="?table=Cross-section%20limits%20for%20lltt,%20ggF,%20tanbeta=0.5">95% CL upper limit on ggF A->ZH(tt) production for tanb=0.5</a> <li><a href="?table=Cross-section%20limits%20for%20lltt,%20ggF,%20tanbeta=1">95% CL upper limit on ggF A->ZH(tt) production for tanb=1</a> <li><a href="?table=Cross-section%20limits%20for%20lltt,%20ggF,%20tanbeta=5">95% CL upper limit on ggF A->ZH(tt) production for tanb=5</a> <li><a href="?table=Cross-section%20limits%20for%20lltt,%20bbA,%20tanbeta=1">95% CL upper limit on bbA A->ZH(tt) production for tanb=1</a> <li><a href="?table=Cross-section%20limits%20for%20lltt,%20bbA,%20tanbeta=5">95% CL upper limit on bbA A->ZH(tt) production for tanb=5</a> <li><a href="?table=Cross-section%20limits%20for%20lltt,%20bbA,%20tanbeta=10">95% CL upper limit on bbA A->ZH(tt) production for tanb=10</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20ggA,%20tanbeta=0.5">95% CL upper limit on ggF A->ZH(bb) production for tanb=0.5</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20ggA,%20tanbeta=1">95% CL upper limit on ggF A->ZH(bb) production for tanb=1</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20ggA,%20tanbeta=5">95% CL upper limit on ggF A->ZH(bb) production for tanb=5</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20bbA,%20tanbeta=1">95% CL upper limit on bbA A->ZH(bb) production for tanb=1</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20bbA,%20tanbeta=5">95% CL upper limit on bbA A->ZH(bb) production for tanb=5</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20bbA,%20tanbeta=10">95% CL upper limit on bbA A->ZH(bb) production for tanb=10</a> <li><a href="?table=Cross-section%20limits%20for%20vvbb,%20bbA,%20tanbeta=20">95% CL upper limit on bbA A->ZH(bb) production for tanb=20</a> </ul> <b>Kinematic distributions:</b> <ul> <li><a href="?table=m(tt),L3hi_Zin,ggF-production">m(tt) distribution in the L3hi_Zin region of the lltt channel</a> <li><a href="?table=m(bb),2tag,0L,ggF-production">m(bb) distribution in the 2 b-tag 0L region of the vvbb channel</a> <li><a href="?table=m(bb),3ptag,0L,bbA-production">m(bb) distribution in the 3p b-tag 0L region of the vvbb channel</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin450,bbA-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=450 GeV hypothesis with the bbA signal shown</a> <li><a href="?table=m(tt),L3hi_Zin,bbA-production">m(tt) distribution in the L3hi_Zin region of the lltt channel with the bbA signal shown</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin350,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=350 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin400,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=400 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin450,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=450 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin500,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=500 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin550,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=550 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin600,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=600 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin700,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=700 GeV hypothesis</a> <li><a href="?table=m(lltt)-m(tt),L3hi_Zin_Hin800,ggF-production">Fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=800 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin130,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=130 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin150,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=150 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin200,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=200 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin250,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=250 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin300,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=300 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin350,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=350 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin400,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=400 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin450,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=450 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin500,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=500 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin600,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=600 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin700,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=700 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,0L_Hin800,ggF-production">Fit discriminant mT(VH) in the 2 b-tag signal region of the vvbb channel for the mH=800 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin130,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=130 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin150,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=150 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin200,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=200 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin250,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=250 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin300,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=300 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin350,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=350 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin400,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=400 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin450,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=450 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin500,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=500 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin600,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=600 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin700,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=700 GeV hypothesis</a> <li><a href="?table=mTVH,3ptag,0L_Hin800,bbA-production">Fit discriminant mT(VH) in the 3p b-tag signal region of the vvbb channel for the mH=800 GeV hypothesis</a> <li><a href="?table=mTVH,2tag,2L">Fit discriminant mT(VH) in the 2L region of the vvbb channel</a> <li><a href="?table=mTVH,2tag,em">Fit discriminant mT(VH) in the em region of the vvbb channel</a> <li><a href="?table=mTVH,3ptag,2L">Fit discriminant mT(VH) in the 2L region of the vvbb channel</a> <li><a href="?table=mTVH,3ptag,em">Fit discriminant mT(VH) in the em region of the vvbb channel</a> <li><a href="?table=lep3pt,L3hi_Zin">pT(lepton,3) distribution in the L3hi_Zin region of the lltt channel</a> <li><a href="?table=etaHrestVH,L3hi_Zin">eta(H,VH rest frame) distribution in the signal region of the lltt channel</a> <li><a href="?table=ETmiss,2tag,0L">ETmiss distribution in the 2 b-tag signal region of the vvbb channel</a> <li><a href="?table=mtopnear,2tag,0L">m(top,near) distribution in the 2 b-tag signal region of the vvbb channel</a> <li><a href="?table=ETmiss,3ptag,0L">ETmiss distribution in the 3p b-tag signal region of the vvbb channel</a> <li><a href="?table=mtopnear,3ptag,0L">m(top,near) distribution in the 3p b-tag signal region of the vvbb channel</a> </ul> <b>Observed local significance:</b> <ul> <li><a href="?table=Local%20significance,%20lltt,%20ggF%20production">ggF A->ZH->lltt signals</a> <li><a href="?table=Local%20significance,%20lltt,%20bbA%20production">bbA A->ZH->lltt signals</a> <li><a href="?table=Local%20significance,%20vvbb,%20ggF%20production">ggF A->ZH->vvbb signals</a> <li><a href="?table=Local%20significance,%20vvbb,%20bbA%20production">bbA A->ZH->vvbb signals</a> </ul> <b>Acceptance and efficiency:</b> <ul> <li><a href="?table=Acceptance*efficiency,%20lltt,%20ggF%20production">ggF A->ZH->lltt signals</a> <li><a href="?table=Acceptance*efficiency,%20lltt,%20bbA%20production">bbA A->ZH->lltt signals</a> <li><a href="?table=Acceptance*efficiency,%20vvbb,%20ggF%20production">ggF A->ZH->vvbb signals</a> <li><a href="?table=Acceptance*efficiency,%20vvbb,%20bbA%20production">bbA A->ZH->vvbb signals</a> </ul>
The distribution of the fit discriminant m(lltt)-m(tt) in the signal region of the lltt channel for the mH=450 GeV hypothesis. <br><br><a href="?table=overview">return to overview</a>
The distribution of the fit discriminant mTVH in the 2 b-tag signal region of the vvbb channel for the mH=300 GeV hypothesis. <br><br><a href="?table=overview">return to overview</a>
A search for nonresonant Higgs boson pair production in the $b\bar{b}\gamma\gamma$ final state is performed using 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. This analysis supersedes and expands upon the previous nonresonant ATLAS results in this final state based on the same data sample. The analysis strategy is optimised to probe anomalous values not only of the Higgs ($H$) boson self-coupling modifier $\kappa_\lambda$ but also of the quartic $HHVV$ ($V=W,Z$) coupling modifier $\kappa_{2V}$. No significant excess above the expected background from Standard Model processes is observed. An observed upper limit $\mu_{HH}<4.0$ is set at 95% confidence level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The 95% confidence intervals for the coupling modifiers are $-1.4<\kappa_\lambda<6.9$ and $-0.5<\kappa_{2V}<2.7$, assuming all other Higgs boson couplings except the one under study are fixed to the Standard Model predictions. The results are interpreted in the Standard Model effective field theory and Higgs effective field theory frameworks in terms of constraints on the couplings of anomalous Higgs boson (self-)interactions.
Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.
Expected (dashed line) value of $-2\ln\Lambda$ as a function of $\kappa_{\lambda}$, when all other coupling modifiers are fixed to their SM predictions.
Observed (solid line) value of $-2\ln\Lambda$ as a function of $\kappa_{2V}$, when all other coupling modifiers are fixed to their SM predictions.
This paper presents a study of $Z \to ll\gamma~$decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton-proton data sample corresponding to an integrated luminosity of 20.2 fb$^{-1}$ collected at a centre-of-mass energy $\sqrt{s}$ = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with state-of-the-art predictions for final-state QED radiation. First measurements of $Z \to ll\gamma\gamma$ decays are also reported.
Unfolded $M(l^{+}\gamma)$ distribution for $Z \to ee\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 63717.4 $\pm$ 252.4, NPowHeg truth =338714.
Unfolded $M(l^{-}\gamma)$ distribution for $Z \to ee\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 63855.8 $\pm$ 252.7 , NPowHeg truth =338708.
Unfolded $M(l^{+}\gamma)$ distribution for $Z \to \mu\mu\gamma$ process with dressed leptons and bkg subtraction. $M_{ll}>20$ GeV. Nexp.un f. = 64809.8 $\pm$ 254.6, NPowHeg truth =634285.
A search for non-resonant Higgs boson pair ($HH$) production is presented, in which one of the Higgs bosons decays to a b-quark pair ($b\bar b$) and the other decays to $WW^*$, $ZZ^*$, or $\tau^+\tau^-$, with in each case a final state with $\ell^+\ell^- +$ neutrinos ($\ell = e, \mu$). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of $140\mathrm{fb}^{-1}$, are used in this analysis. Events are selected to have exactly two $b$-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the $HH$ events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter $\kappa_\lambda$ and the quadrilinear coupling parameter $\kappa_{2V}$ are each separately constrained by this analysis to be within the ranges ${[-6.2, 13.3]}$ and ${[-0.17, 2.4]}$, respectively, at 95% confidence level, when all other parameters are fixed.
Pre-fit yields of the $t\bar{t}$, $Z$+HF and $Wt$ CRs, both for the ggF and VBF event selection, as well as the highest-score bins, numbered from high (VBF-SR 1 and ggF-SR 1) to low score (VBF-SR 5 and ggF-SR 7), of the BDT and DNN output distribution in the VBF and ggF event categories, respectively, as used in the final result. The shaded bands include both statistical and systematic uncertainties.
Post-fit yields from the signal+background fit of the $t\bar{t}$, $Z$+HF and $Wt$ CRs, both for the ggF and VBF event selections, as well as the highest-score bins, numbered from high (VBF-SR 1 and ggF-SR 1) to low score (VBF-SR 5 and ggF-SR 7), of the BDT and DNN output distribution in the VBF and ggF event categories respectively as used in the final result. The fit is a conditional fit with the signal strength fixed to the observed upper limit of $\mu_{HH} = 9.7$. The shaded bands include both statistical and systematic uncertainties.
Observed and expected upper limits on the ratios of the Higgs boson pair production cross-section to the corresponding Standard Model prediction $\sigma_{HH}/\sigma^\mathrm{SM}_{HH}$ for the ggF $HH$ signal only (top row), the VBF $HH$ signal only while considering ggF $HH$ as background (second row) and the combined ggF+VBF $HH$ signal considering only the ggF SR (third row) and considering all SRs (bottom row) at a 95% confidence level. The relative ratio between the ggF and VBF production modes is fixed to the SM value.
A study of the polarisation and CP properties in $ZZ$ production is presented. The used data set corresponds to an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of $13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. The $ZZ$ candidate events are reconstructed using two same-flavour opposite-charge electron or muon pairs. The production of two longitudinally polarised $Z$ bosons is measured with a significance of 4.3 standard deviations, and its cross-section is measured in a fiducial phase space to be $2.45 \pm 0.60$ fb, consistent with the next-to-leading-order Standard Model prediction. The inclusive differential cross-section as a function of a CP-sensitive angular observable is also measured. The results are used to constrain anomalous CP-odd neutral triple gauge couplings.
Unfolded differential cross-section as a function of the Optimal Observable $\mathcal{O}_{T_{yz,1} T_{yz,3}}$
Measurements of the differential production cross-sections of prompt and non-prompt $J/\psi$ and $\psi(2$S$)$ mesons with transverse momenta between 8 and 360 GeV and rapidity in the range $|y|<2$ are reported. Furthermore, measurements of the non-prompt fractions of $J/\psi$ and $\psi(2$S$)$, and the prompt and non-prompt $\psi(2$S$)$-to-$J/\psi$ production ratios, are presented. The analysis is performed using 140 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data recorded by the ATLAS detector at the LHC during the years 2015-2018.
Summary of results for cross-section of prompt $J/\psi$ decaying to a muon pair for 13 TeV data in fb/GeV. Uncertainties are statistical and systematic, respectively.
Summary of results for cross-section of non-prompt $J/\psi$ decaying to a muon pair for 13 TeV data in fb/GeV. Uncertainties are statistical and systematic, respectively.
Summary of results for cross-section of prompt $\psi(2S)$ decaying to a muon pair for 13 TeV data in fb/GeV. Uncertainties are statistical and systematic, respectively.
This paper presents for the first time a precise measurement of the production properties of the Z boson in the full phase space of the decay leptons. This is in contrast to the many previous precise unfolded measurements performed in the fiducial phase space of the decay leptons. The measurement is obtained from proton-proton collision data collected by the ATLAS experiment in 2012 at $\sqrt s$ = 8 TeV at the LHC and corresponding to an integrated luminosity of 20.2 fb$^{-1}$. The results, based on a total of 15.3 million Z-boson decays to electron and muon pairs, extend and improve a previous measurement of the full set of angular coefficients describing Z-boson decay. The double-differential cross-section distributions in Z-boson transverse momentum p$_T$ and rapidity y are measured in the pole region, defined as 80 $<$ m $<$ 100 GeV, over the range $|y| <$ 3.6. The total uncertainty of the normalised cross-section measurements in the peak region of the p$_T$ distribution is dominated by statistical uncertainties over the full range and increases as a function of rapidity from 0.5-1.0% for $|y| <$ 2.0 to 2-7% at higher rapidities. The results for the rapidity-dependent transverse momentum distributions are compared to state-of-the-art QCD predictions, which combine in the best cases approximate N$^4$LL resummation with N$^3$LO fixed-order perturbative calculations. The differential rapidity distributions integrated over p$_T$ are even more precise, with accuracies from 0.2-0.3% for $|y| <$ 2.0 to 0.4-0.9% at higher rapidities, and are compared to fixed-order QCD predictions using the most recent parton distribution functions. The agreement between data and predictions is quite good in most cases.
Measured $p_T$ cross sections in full-lepton phase space for |y| < 0.4.
Measured $p_T$ cross sections in full-lepton phase space for 0.4 < |y| < 0.8.
Measured $p_T$ cross sections in full-lepton phase space for 0.8 < |y| < 1.2.
The first evidence for the Higgs boson decay to a $Z$ boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton-proton collision data sets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140 fb$^{-1}$ for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is $2.2\pm0.7$ times the Standard Model prediction, and agrees with the theoretical expectation within 1.9 standard deviations.
The negative profile log-likelihood test statistic, where $\Lambda$ represents the likelihood ratio, as a function of the signal strength $\mu$ derived from the ATLAS data, the CMS data, and the combined result.
Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton collision data collected by ATLAS at $\sqrt{s}=13$ TeV and with an integrated luminosity of 140 fb$^{-1}$. The data are corrected for the effects of detector inefficiency and resolution and are compared to state-of-the-art Monte Carlo event generator predictions. The differential cross-sections are used to search for anomalous weak-boson self-interactions that are induced by dimension-six and dimension-eight operators in Standard Model effective field theory.
Predicted and observed yields as a function of $m_{jj}$ in the VBS-Enhanced region. Overflow events are included in the last bin of the distribution.
Predicted and observed yields as a function of $m_{jj}$ in the VBS-Suppressed region. Overflow events are included in the last bin of the distribution.
Predicted and observed yields as a function of $m_{4\ell}$ in the VBS-Enhanced region. Overflow events are included in the last bin of the distribution.
A search for a new massive charged gauge boson, $W'$, is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton-proton collisions at a centre-of-mass energy of $\sqrt{s} =13$ TeV, and corresponds to an integrated luminosity of 139 fb$^{-1}$. The reconstructed $tb$ invariant mass is used to search for a $W'$ boson decaying into a top quark and a bottom quark. The result is interpreted in terms of a $W'$ boson with purely right-handed or left-handed chirality in a mass range of 0.5-6 TeV. Different values for the coupling of the $W'$ boson to the top and bottom quarks are considered, taking into account interference with single-top-quark production in the $s$-channel. No significant deviation from the background prediction is observed. The results are expressed as upper limits on the $W' \rightarrow tb$ production cross-section times branching ratio as a function of the $W'$-boson mass and in the plane of the coupling vs the $W'$-boson mass.
<b>- - - - - - - - Overview of HEPData Record - - - - - - - -</b> <br><br> <b>Exclusion contours:</b> <ul> <li><a href="?table=contour_lh">$W^{\prime}_L$ exclusion contour</a> <li><a href="?table=contour_rh">$W^{\prime}_R$ exclusion contour</a> </ul> <b>Upper limits:</b> <ul> <li><a href="?table=limit_lh_gf05">$W^{\prime}_L$ $g^{\prime}/g$ = 0.5 upper limit</a> <li><a href="?table=limit_lh_gf10">$W^{\prime}_L$ $g^{\prime}/g$ = 1.0 upper limit</a> <li><a href="?table=limit_lh_gf20">$W^{\prime}_L$ $g^{\prime}/g$ = 2.0 upper limit</a> <li><a href="?table=limit_rh_gf05">$W^{\prime}_R$ $g^{\prime}/g$ = 0.5 upper limit</a> <li><a href="?table=limit_rh_gf10">$W^{\prime}_R$ $g^{\prime}/g$ = 1.0 upper limit</a> <li><a href="?table=limit_rh_gf20">$W^{\prime}_R$ $g^{\prime}/g$ = 2.0 upper limit</a> </ul> <b>Kinematic distributions:</b> <ul> <li><a href="?table=0l_sr1">0L channel Signal Region 1</a> <li><a href="?table=0l_sr2">0L channel Signal Region 2</a> <li><a href="?table=0l_sr3">0L channel Signal Region 3</a> <li><a href="?table=0l_vr">0L channel Validation Region</a> <li><a href="?table=1l_sr_2j1b">1L channel 2j1b Signal Region</a> <li><a href="?table=1l_sr_3j1b">1L channel 3j1b Signal Region</a> <li><a href="?table=1l_sr_2j2b">1L channel 2j2b Signal Region</a> <li><a href="?table=1l_sr_3j2b">1L channel 3j2b Signal Region</a> <li><a href="?table=1l_cr_2j1b">1L channel 2j1b Control Region</a> <li><a href="?table=1l_cr_3j1b">1L channel 3j1b Control Region</a> <li><a href="?table=1l_vr_2j1b">1L channel 2j1b Validation Region</a> <li><a href="?table=1l_vr_3j1b">1L channel 3j1b Validation Region</a> </ul> <b>Acceptance and efficiencies:</b> <ul> <li><a href="?table=acc_0l_lh_gf10">0L channel $W^{\prime}_L$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_0l_lh_gf05">0L channel $W^{\prime}_L$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_0l_lh_gf20">0L channel $W^{\prime}_L$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_lh_gf10">1L channel $W^{\prime}_L$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_lh_gf05">1L channel $W^{\prime}_L$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_1l_lh_gf20">1L channel $W^{\prime}_L$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> <li><a href="?table=acc_0l_rh_gf10">0L channel $W^{\prime}_R$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_0l_rh_gf05">0L channel $W^{\prime}_R$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_0l_rh_gf20">0L channel $W^{\prime}_R$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_rh_gf10">1L channel $W^{\prime}_R$ $g^{\prime}/g$ = 1.0 Acc. X Eff.</a> <li><a href="?table=acc_1l_rh_gf05">1L channel $W^{\prime}_R$ $g^{\prime}/g$ = 0.5 Acc. X Eff.</a> <li><a href="?table=acc_1l_rh_gf20">1L channel $W^{\prime}_R$ $g^{\prime}/g$ = 2.0 Acc. X Eff.</a> </ul>
Distribution (events/100 GeV) of the reconstructed $m_{tb}$ for data and backgrounds in the 0-lepton channel's signal region 1 after the background-only fit to data. The systematics uncertainty is shown for the post-fit background sum, including the background statistical uncertainty. The individual background components are obtained after the fit, too. There are also the pre-fit background sum and the expected signal distribution. The distribution of the $W^{\prime}$ boson signal for a mass of 3 TeV is normalised to the predicted cross-section. The last bin in each distribution includes overflow.
Distribution (events/100 GeV) of the reconstructed $m_{tb}$ for data and backgrounds in the 0-lepton channel's signal region 2 after the background-only fit to data. The systematics uncertainty is shown for the post-fit background sum, including the background statistical uncertainty. The individual background components are obtained after the fit, too. There are also the pre-fit background sum and the expected signal distribution. The distribution of the $W^{\prime}$ boson signal for a mass of 3 TeV is normalised to the predicted cross-section. The last bin in each distribution includes overflow.
We present a search for magnetic monopoles and high-electric-charge objects using LHC Run 2 $\sqrt{s} =$13 TeV proton$-$proton collisions recorded by the ATLAS detector. A total integrated luminosity of 138 fb$^{-1}$ was collected by a specialized trigger. No highly ionizing particle candidate was observed. Considering the Drell-Yan and photon-fusion pair production mechanisms as benchmark models, cross-section upper limits are presented for spin-0 and spin-$\frac{1}{2}$ magnetic monopoles of magnetic charge $1g_\textrm{D}$ and $2g_\textrm{D}$ and for high-electric-charge objects of electric charge $20 \leq |z| \leq 100$, for masses between 200 GeV and 4000 GeV. The search improves by approximately a factor of three the previous cross-section limits on the Drell-Yan production of magnetic monopoles and high-electric charge objects. Also, the first ATLAS limits on the photon-fusion pair production mechanism of magnetic monopoles and high-electric-charge objects have been obtained.
Observed 95% CL upper limits on the cross section for all masses and charges of Drell-Yan spin-0 monopoles production as a function of mass for magnetic charges $|g|=1g_D$ and $|g|=2g_D$.
Observed 95% CL upper limits on the cross section for all masses and charges of Drell-Yan spin-1/2 monopoles production as a function of mass for magnetic charges $|g|=1g_D$ and $|g|=2g_D$.
Observed 95% CL upper limits on the cross section for all masses and charges of photon-fusion pair-produced spin-0 monopoles as a function of mass for magnetic charges $|g|=1g_D$ and $|g|=2g_D$.
A search for quantum black holes in electron+jet and muon+jet invariant mass spectra is performed with 140 fb$^{-1}$ of data collected by the ATLAS detector in proton-proton collisions at $\sqrt{s}$ = 13 TeV at the Large Hadron Collider. The observed invariant mass spectrum of lepton+jet pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross-sections times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model.
The 95% CL model-independent upper limits on $\sigma \times Br$ for the non-SM signal production with decay into the lepton+jet. The limits take into account statistical and systematic uncertainties. Circles along the solid red line indicate the lower border of the SR (threshold of SR, Th$_\mathrm{SR}$), above which the observed limit is computed. The expected limits are shown by the dashed line. The $\pm 1\sigma$ and $\pm 2\sigma$ bands of expected limits are shown in green and yellow, respectively. The limits are obtained with pseudo-experiments.
The combined 95% CL upper limits on $\sigma \times Br$ as a function of threshold mass, $M_\mathrm{th}$, for QBH production with decay into lepton+jet for ADD-model (extra dimensions n = 6). The limits take into account statistical and systematic uncertainties. Circles along the solid red line indicate the mass $M_\mathrm{th}$ of the signal where the observed limit is computed. The expected limits are shown by the dashed line. The $\pm 1\sigma$ and $\pm 2\sigma$ bands are shown in green and yellow, respectively. The theoretically predicted $\sigma \times Br$ for the QBH production and decay is shown as the solid blue curve with squares.
The combined 95% CL upper limits on $\sigma \times Br$ as a function of threshold mass, $M_\mathrm{th}$, for QBH production with decay into lepton+jet for RS1-model (extra dimensions n = 1). The limits take into account statistical and systematic uncertainties. Circles along the solid red line indicate the mass $M_\mathrm{th}$ of the signal where the observed limit is computed. The expected limits are shown by the dashed line. The $\pm 1\sigma$ and $\pm 2\sigma$ bands are shown in green and yellow, respectively. The theoretically predicted $\sigma \times Br$ for the QBH production and decay is shown as the solid blue curve with squares.
New particles with large masses that decay into hadronically interacting particles are predicted by many models of physics beyond the Standard Model. A search for a massive resonance that decays into pairs of dijet resonances is performed using 140 fb$^{-1}$ of proton$-$proton collisions at $\sqrt{s}=13$ TeV recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. Resonances are searched for in the invariant mass of the tetrajet system, and in the average invariant mass of the pair of dijet systems. A data-driven background estimate is obtained by fitting the tetrajet and dijet invariant mass distributions with a four-parameter dijet function and a search for local excesses from resonant production of dijet pairs is performed. No significant excess of events beyond the Standard Model expectation is observed, and upper limits are set on the production cross-sections of new physics scenarios.
The average tetrajet invariant mass distributions in data, along with the fitted background estimates for 0.10 < $\alpha$ < 0.12.
The average tetrajet invariant mass distributions in data, along with the fitted background estimates for 0.12 < $\alpha$ < 0.14.
The average tetrajet invariant mass distributions in data, along with the fitted background estimates for 0.14 < $\alpha$ < 0.16.
A search for a new heavy scalar particle $X$ decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle $S$ is presented. The search uses a proton-proton ($pp$) collision data sample with an integrated luminosity of 140 fb$^{-1}$ recorded at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ATLAS detector at the Large Hadron Collider. The most sensitive mass parameter space is explored in $X$ mass ranging from 500 to 1500 GeV, with the corresponding $S$ mass in the range 200-500 GeV. The search selects events with two hadronically decaying $\tau$-lepton candidates from $H\to \tau^+\tau^-$ decays and one or two light leptons ($\ell=e,\,\mu$) from $S\to VV$ ($V = W,\,Z$) decays while the remaining $V$ boson decays hadronically or to neutrinos. A multivariate discriminant based on event kinematics is used to separate the signal from the background. No excess is observed beyond the expected SM background and 95% confidence level upper limits between 72 fb and 542 fb are derived on the cross-section $\sigma(pp\to X\to SH)$ assuming the same SM-Higgs boson-like decay branching ratios for the $S\to VV$ decay. Upper limits on the visible cross-sections $\sigma(pp\to X\to SH \to WW\tau\tau)$ and $\sigma(pp\to X\to SH \to ZZ\tau\tau)$ are also set in the ranges 3-26 fb and 6-33 fb, respectively.
Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH)$ obtained from $WW1\ell2\tau_{\mathrm{had}}$, $WW2\ell2\tau_{\mathrm{had}}$, $ZZ2\ell2\tau_{\mathrm{had}}$, and their combination, as a function of combined $m_{S}$ and $m_{X}$ masses ($m_{S}$+$m_{X}/25$) in GeV.
Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH\to WW\tau\tau)$ obtained from the combination of $WW1\ell2\tau_{\mathrm{had}}$ and $WW2\ell2\tau_{\mathrm{had}}$ channels, as a function of combined $m_{S}$ and $m_{X}$ masses ($m_{S}$+$m_{X}/25$) in GeV. The NMSSM scans of the allowed cross-sections for $\sigma(pp\to X\to SH\to WW\tau\tau)$ are also compared.
Observed and expected 95% CL upper limits are shown for $\sigma(pp\to X\to SH\to ZZ\tau\tau)$ obtained from $ZZ2\ell2\tau_{\mathrm{had}}$ channel, as a function of combined $m_{S}$ and $m_{X}$ masses ($m_{S}$+$m_{X}/25$) in GeV. The NMSSM scans of the allowed cross-sections for $\sigma(pp\to X\to SH\to ZZ\tau\tau)$ are also compared.
Searches for new resonances are performed using an unsupervised anomaly-detection technique. Events with at least one electron or muon are selected from 140 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 13$ TeV recorded by ATLAS at the Large Hadron Collider. The approach involves training an autoencoder on data, and subsequently defining anomalous regions based on the reconstruction loss of the decoder. Studies focus on nine invariant mass spectra that contain pairs of objects consisting of one light jet or $b$-jet and either one lepton ($e$, $\mu$), photon, or second light jet or $b$-jet in the anomalous regions. No significant deviations from the background hypotheses are observed.
Distributions of the anomaly score from the AE for data and five benchmark BSM models. Their legends, from top to bottom, are; (1) charged Higgs boson production in association with a top quark, $tbH^{+}$ with $H^{+} \rightarrow t\bar{b}$; (2) a Kaluza-Klein gauge boson, $W_{KK}$, with the SM $W$ boson and a radion $\phi$; (3) a $Z'$ boson decaying to a composite lepton $E$ and $\ell$, with $E \rightarrow Z\ell$ with a mass of 0.5 TeV; (4) the SSM $W$'$\rightarrow W Z' \rightarrow \ell\nu q\bar{q}$; (5) a simplified dark-matter model with an $Z$ axial-vector mediator $Z' \rightarrow q\bar{q}$, where one of the quarks radiates a $W$ boson decaying to $\ell\nu$. The BSM predictions represent the expected number of events from 140 $fb^{-1}$ of data for heavy particle ($H^{+}$ ,$W_{KK}$ , $Z'$ , $W'$ and $Z'$, respectively) masses around 2 TeV. The distributions for the BSM models are smoothed to remove fluctuations due to low MC event counts. The vertical lines indicate the start of the three anomaly regions (ARs). The labels of the three ARs indicate the visible cross section for hypothetical processes yielding the same number of events as observed in the 140 $fb^{-1}$ dataset. The AE is applied to preselected events without any requirements on invariant mass distributions.
Invariant mass distributions of jet+Y for $M_{jY}$ > 0.3 TeV in the 10 pb AR along with the fit of Eq. (1). The fits are represented by the lines, while the associated statistical uncertainties are indicated by the shaded bands. The lower panels show the bin-by-bin significances of deviations from the fit, calculated as $(d_{\textit{i}} - f_{i})/\delta_{\textit{i}}$, where $d_{i}$ is the data yield, $f_{\textit{i}}$ is the fit value, and $\delta_{i}$ is the data uncertainty in the $\textit{i}$-th bin.
Values of $\Delta Z$ for the discovery sensitivity, as defined in the text, as a function of the invariant mass $\textit{m}$. The j+j invariant mass distribution is calculated in the 10 pb AR. Positive percentages indicate improvements in sensitivity. Horizontal dashed lines are drawn at 100% and 200% to guide the eye. The five benchmark BSM models are (1) charged Higgs boson production in association with a top quark, $tbH^{+}$ with $H^{+} \rightarrow t\bar{b}$; (2) a Kaluza-Klein gauge boson, $W_{KK}$, with the SM $W$ boson and a radion $\phi$; (3) a $Z'$ boson decaying to a composite lepton $E$ and $\ell$, with $E \rightarrow Z\ell$; (4) the sequential standard model $W' \rightarrow W Z' \rightarrow \ell\nu q\bar{q}$; (5) a simplified dark-matter model with an axial-vector mediator $Z' \rightarrow q\bar{q}$, where one of the quarks radiates a $W$ boson decaying to $\ell\nu$. The multiple markers shown for the composite-lepton model at the same invariant mass values correspond to different composite lepton ($E$) masses between 0.25 and 3.5 TeV. The center positions of the markers are set to the masses of the corresponding heavy particles.
A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb$^{-1}$ of proton$-$proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of the $WZ$+jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models considering gluino (squark) pair production, gluino (squark) masses up to 2.2 (1.7) TeV are excluded at 95% confidence level.
Observed exclusion limits at 95% CL from Fig 7(a) for $\tilde{g}$ decays into SM gauge bosons and $\tilde{\chi}^{0}_{1}$
Positive one $\sigma$ observed exclusion limits at 95% CL from Fig 7(a) for $\tilde{g}$ decays into SM gauge bosons and $\tilde{\chi}^{0}_{1}$
Negative one $\sigma$ observed exclusion limits at 95% CL from Fig 7(a) for $\tilde{g}$ decays into SM gauge bosons and $\tilde{\chi}^{0}_{1}$
A search for leptoquark pair production decaying into $te^- \bar{t}e^+$ or $t\mu^- \bar{t}\mu^+$ in final states with multiple leptons is presented. The search is based on a dataset of $pp$ collisions at $\sqrt{s}$=13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139~fb$^{-1}$. Events are selected with two or more light leptons (electron or muon) and at least two jets out of which at least one jet is identified as coming from a $b$-hadron. Four signal regions, with the requirement of at least three light leptons, are considered based on the number of leptons of a given flavour. The main background processes are estimated using dedicated control regions in a simultaneous fit with the signal regions to data. No excess above the Standard Model background prediction is observed and 95% confidence level limits on the production cross section times branching ratio are derived as a function of the leptoquark mass. Under the assumption of exclusive decays into $te^{-}$ ($t\mu^{-}$), the corresponding lower limit on the scalar mixed-generation leptoquark mass $m_{\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}}$ is at 1.58 (1.59) TeV and on the vector leptoquark mass $m_{\tilde{U}_1}$ at 1.67 (1.67) TeV in the minimal coupling scenario and at 1.95 (1.95) TeV in the Yang-Mills scenario.
Selection efficiency times acceptance summed over two signal regions for the scalar leptoquark signals as a function of $m_{\mathrm{LQ}_{mix}^{\mathrm{d}}}$, assuming B = 1.
Selection efficiency times acceptance summed over two signal regions for the vector leptoquark signals as a function of $m_{\tilde{U}_{1}}$, assuming B = 1 and Yang-Mills coupling scenario.
Summary of the observed and expected 95% CL upper limits on the cross section for $\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}$ pair production as a function of $m_{\mathrm{LQ}_{\mathrm{mix}}^{\mathrm{d}}}$ under the assumptions of B(LQ$\rightarrow te$)=1.
A search for events with a dark photon produced in association with a dark Higgs boson via rare decays of the Standard Model $Z$ boson is presented, using 139 fb$^{-1}$ of $\sqrt{s} = 13$ TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider. The dark Higgs boson decays into a pair of dark photons, and at least two of the three dark photons must each decay into a pair of electrons or muons, resulting in at least two same-flavor opposite-charge lepton pairs in the final state. The data are found to be consistent with the background prediction, and upper limits are set on the dark photon's coupling to the dark Higgs boson times the kinetic mixing between the Standard Model photon and the dark photon, $\alpha_{D}\varepsilon^2$, in the dark photon mass range of $[5, 40]$ GeV except for the $\Upsilon$ mass window $[8.8, 11.1]$ GeV. This search explores new parameter space not previously excluded by other experiments.
Observed and expected upper limits at 95% CL on the production cross-section times branching fraction as a function of $m_{A'}$ at dark Higgs boson mass of 20 GeV
Observed and expected upper limits at 95% CL on the production cross-section times branching fraction as a function of $m_{A'}$ at dark Higgs boson mass of 30 GeV
Observed and expected upper limits at 95% CL on the production cross-section times branching fraction as a function of $m_{A'}$ at dark Higgs boson mass of 40 GeV
A measurement of novel event shapes quantifying the isotropy of collider events is performed in 140 fb$^{-1}$ of proton-proton collisions with $\sqrt s=13$ TeV centre-of-mass energy recorded with the ATLAS detector at CERN's Large Hadron Collider. These event shapes are defined as the Wasserstein distance between collider events and isotropic reference geometries. This distance is evaluated by solving optimal transport problems, using the 'Energy-Mover's Distance'. Isotropic references with cylindrical and circular symmetries are studied, to probe the symmetries of interest at hadron colliders. The novel event-shape observables defined in this way are infrared- and collinear-safe, have improved dynamic range and have greater sensitivity to isotropic radiation patterns than other event shapes. The measured event-shape variables are corrected for detector effects, and presented in inclusive bins of jet multiplicity and the scalar sum of the two leading jets' transverse momenta. The measured distributions are provided as inputs to future Monte Carlo tuning campaigns and other studies probing fundamental properties of QCD and the production of hadronic final states up to the TeV-scale.
IRing2 for HT2>=500 GeV, NJets>=2
IRing2 for HT2>=500 GeV, NJets>=3
IRing2 for HT2>=500 GeV, NJets>=4
This Letter reports the observation of $WZ\gamma$ production and a measurement of its cross-section using 140.1 $\pm$ 1.2 fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The $WZ\gamma$ production cross-section, with both the $W$ and $Z$ bosons decaying leptonically, $pp \rightarrow WZ\gamma \rightarrow {\ell'}^{\pm}\nu\ell^{+}\ell^{-}\gamma$ ($\ell^{(')} = e, \mu$), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross-section is found to be 2.01 $\pm$ 0.30 (stat.) $\pm$ 0.16 (syst) fb. The corresponding Standard Model predicted cross-section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50 $\pm$ 0.06 fb. The observed significance of the $WZ\gamma$ signal is 6.3$\sigma$, compared with an expected significance of 5.0$\sigma$.
Events in bins of the photon $p_{\mathrm{T}}^{\gamma}$ in the SR.
Events in bins of the $p_{\mathrm{T}}^{\ell_{1}}$ in the SR.
Events in bins of the $m(\ell\ell)$ in the SR.
A search for leptoquarks decaying into the $b\tau$ final state is performed using Run 2 proton-proton collision data from the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb$^{-1}$ at $\sqrt{s} = 13$ TeV recorded by the ATLAS detector. The benchmark models considered in this search are vector leptoquarks with electric charge of 2/3e and scalar leptoquarks with an electric charge of 4/3e. No significant excess above the Standard Model prediction is observed, and 95% confidence level upper limits are set on the cross-section times branching fraction of leptoquarks decaying into $b\tau$. For the vector leptoquark production two models are considered: the Yang-Mills and Minimal coupling models. In the Yang-Mills (Minimal coupling) scenario, vector leptoquarks with a mass below 1.58 (1.35) TeV are excluded for a gauge coupling of 1.0 and below 2.05 (1.99) TeV for a gauge coupling of 2.5. In the case of scalar leptoquarks, masses below 1.28 TeV (1.53 TeV) are excluded for a Yukawa coupling of 1.0 (2.5). Finally, an interpretation of the results with minimal model dependence is performed for each of the signal region categories, and limits on the visible cross-section for beyond the Standard Model processes are provided.
Observed (solid line) and expected (dashed line) 95% CL upper limits on the cross-section of single plus non-resonant plus pair vector LQ production from the combination of the high b-jet $p_{T}$ signal region for the $\tau_\text{lep}\tau_\text{had}$ and $\tau_\text{had}\tau_\text{had}$ channels. [$U_1^{YM}$ model ($\kappa$ = 0) with $\lambda$ = 1.0]
Observed (solid line) and expected (dashed line) 95% CL upper limits on the cross-section of single plus non-resonant plus pair vector LQ production from the combination of the high b-jet $p_{T}$ signal region for the $\tau_\text{lep}\tau_\text{had}$ and $\tau_\text{had}\tau_\text{had}$ channels. [$U_1^{YM}$ model ($\kappa$ = 0) with $\lambda$ = 1.7]
Observed (solid line) and expected (dashed line) 95% CL upper limits on the cross-section of single plus non-resonant plus pair vector LQ production from the combination of the high b-jet $p_{T}$ signal region for the $\tau_\text{lep}\tau_\text{had}$ and $\tau_\text{had}\tau_\text{had}$ channels. [$U_1^{YM}$ model ($\kappa$ = 0) with $\lambda$ = 2.5]
A search for Majorana neutrinos in same-sign $WW$ scattering events is presented. The analysis uses $\sqrt{s}= 13$ TeV proton-proton collision data with an integrated luminosity of 140 fb$^{-1}$ recorded during 2015-2018 by the ATLAS detector at the Large Hadron Collider. The analysis targets final states including exactly two same-sign muons and at least two hadronic jets well separated in rapidity. The modelling of the main backgrounds, from Standard Model same-sign $WW$ scattering and $WZ$ production, is constrained with data in dedicated signal-depleted control regions. The distribution of the transverse momentum of the second-hardest muon is used to search for signals originating from a heavy Majorana neutrino with a mass between 50 GeV and 20 TeV. No significant excess is observed over the background expectation. The results are interpreted in a benchmark scenario of the Phenomenological Type-I Seesaw model. In addition, the sensitivity to the Weinberg operator is investigated. Upper limits at the 95% confidence level are placed on the squared muon-neutrino-heavy-neutrino mass-mixing matrix element $\vert V_{\mu N} \vert^{2}$ as a function of the heavy Majorana neutrino's mass $m_N$, and on the effective $\mu\mu$ Majorana neutrino mass $|m_{\mu\mu}|$.
Observed and expected 95% CL upper limits on the heavy Majorana neutrino mixing element $\vert V_{\mu N} \vert^{2}$ as a function of $m_N$ in the Phenomenological Type-I Seesaw model.
Cutflow for a selection of signal samples used in this analysis. The flavour-aligned scenario (in which $\vert V_{\mu N} \vert^{2}=1$) is considered for heavy Majorana neutrino samples. The event yields include all correction factors applied to simulation, and is normalised to 140 fb$^{-1}$. The `Skim' selection requires 2 baseline muons and 2 jets satisfying the object definitions described in Section 3 and $m_{jj} > 150$ GeV. Uncertainties are statistical only.
A search for dark matter produced in association with a Higgs boson in final states with two hadronically decaying $\tau$-leptons and missing transverse momentum is presented. The analysis uses $139$ fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. No evidence for physics beyond the Standard Model is found. The results are interpreted in terms of a 2HDM+$a$ model. Exclusion limits at 95% confidence level are derived. Model-independent limits are also set on the visible cross section for processes beyond the Standard Model producing missing transverse momentum in association with a Higgs boson decaying to $\tau$-leptons.
<b>- - - - - - - - Overview of HEPData Record - - - - - - - -</b> <br><br> <b>CLs and CLs+b values</b> <ul> <li><a href=?table=CLs_tanb_mA_grid_Expected>Expected CLs values in mA vs tanB grid, Low mA SR</a> <li><a href=?table=CLs_tanb_mA_grid_Observed>Observed CLs values in mA vs tanB grid, Low mA SR</a> <li><a href=?table=CLs_ma_mA_grid_HighmA_SR_Expected>Expected CLs values in mA vs ma grid, High mA SR</a> <li><a href=?table=CLs_ma_mA_grid_HighmA_SR_Observed>Observed CLs values in mA vs ma grid, High mA SR</a> <li><a href=?table=CLs_ma_mA_grid_LowmA_SR_Expected>Expected CLs values in mA vs ma grid, Low mA SR</a> <li><a href=?table=CLs_ma_mA_grid_LowmA_SR_Observed>Observed CLs values in mA vs ma grid, Low mA SR</a> <li><a href=?table=CLsplusb_tanb_mA_grid>CLs+b values in mA vs tanB grid, Low mA SR</a> <li><a href=?table=CLsplusb_ma_mA_grid_HighmA_SR>CLs+b values in mA vs ma grid, High mA SR</a> <li><a href=?table=CLsplusb_ma_mA_grid_LowmA_SR>CLs+b values in mA vs ma grid, Low mA SR</a> </ul> <b>Cutflow tables</b> <ul> <li><a href=?table=Cutflows_ggf_LowmA_SR>Low mA SR, ggF production</a> <li><a href=?table=Cutflows_ggf_HighmA_SR>High mA SR, ggF production</a> <li><a href=?table=Cutflows_bb_LowmA_SR>Low mA SR, bb production</a> <li><a href=?table=Cutflows_bb_HighmA_SR>High mA SR, bb production</a> </ul> <b>Kinematic Distributions</b> <ul> <li><a href=?table=KinDist_LowmA_SR>Low mA SR mTtau1+mTtau2 distribution</a> <li><a href=?table=KinDist_HighmA_SR>High mA SR mTtau1+mTtau2 distribution</a> </ul> <b>Limits</b> <ul> <li><a href=?table=Expected_95%_CL_exclusion_limit_mAma_grid>Expected 95% CL exclusion limit in mA vs ma grid</a> <li><a href=?table=Observed_95%_CL_exclusion_limit_mAma_grid>Observed 95% CL exclusion limit in mA vs ma grid</a> <li><a href=?table=Expected_pm1sigma_95%_CL_exclusion_limit_mAma_grid>Expected +-1 sigma 95% CL exclusion limit in mA vs ma grid</a> <li><a href=?table=Expected_95%_CL_exclusion_limit_mAtanB_grid>Expected 95% CL exclusion limit in mA vs tanB grid</a> <li><a href=?table=Observed_95%_CL_exclusion_limit_mAtanB_grid>Observed 95% CL exclusion limit in mA vs tanB grid</a> <li><a href=?table=Expected_pm1sigma_95%_CL_exclusion_limit_mAtanB_grid>Expected +-1 sigma 95% CL exclusion limit in tanB grid</a> </ul> <b>Acceptance and efficiency</b> <ul> <li><a href=?table=table1>Acceptance, High mA SR, mA vs tanB grid, 400-750 GeV, bb prod</a> <li><a href=?table=table2>Acceptance, High mA SR, mA vs tanB grid, >750 GeV, bb prod</a> <li><a href=?table=table3>Acceptance, Low mA SR, mA vs tanB grid, 100-250 GeV, bb prod</a> <li><a href=?table=table4>Acceptance, Low mA SR, mA vs tanB grid, 250-400 GeV, bb prod</a> <li><a href=?table=table5>Acceptance, Low mA SR, mA vs tanB grid, 400-550 GeV, bb prod</a> <li><a href=?table=table6>Acceptance, Low mA SR, mA vs tanB grid, >550 GeV, bb prod</a> <li><a href=?table=table7>Acceptance, High mA SR, mA vs ma grid, 400-750 GeV, bb prod</a> <li><a href=?table=table8>Acceptance, High mA SR, mA vs ma grid, >750 GeV, bb prod</a> <li><a href=?table=table9>Acceptance, Low mA SR, mA vs ma grid, 100-250 GeV, bb prod</a> <li><a href=?table=table10>Acceptance, Low mA SR, mA vs ma grid, 250-400 GeV, bb prod</a> <li><a href=?table=table11>Acceptance, Low mA SR, mA vs ma grid, 400-550 GeV, bb prod</a> <li><a href=?table=table12>Acceptance, Low mA SR, mA vs ma grid, >550 GeV, bb prod</a> <li><a href=?table=table13>Acceptance, High mA SR, mA vs tanB grid, 400-750 GeV, ggF prod</a> <li><a href=?table=table14>Acceptance, High mA SR, mA vs tanB grid, >750 GeV, ggF prod</a> <li><a href=?table=table15>Acceptance, Low mA SR, mA vs tanB grid, 100-250 GeV, ggF prod</a> <li><a href=?table=table16>Acceptance, Low mA SR, mA vs tanB grid, 250-400 GeV, ggF prod</a> <li><a href=?table=table17>Acceptance, Low mA SR, mA vs tanB grid, 400-550 GeV, ggF prod</a> <li><a href=?table=table18>Acceptance, Low mA SR, mA vs tanB grid, >550 GeV, ggF prod</a> <li><a href=?table=table19>Acceptance, High mA SR, mA vs ma grid, 400-750 GeV, ggF prod</a> <li><a href=?table=table20>Acceptance, High mA SR, mA vs ma grid, >750 GeV, ggF prod</a> <li><a href=?table=table21>Acceptance, Low mA SR, mA vs ma grid, 100-250 GeV, ggF prod</a> <li><a href=?table=table22>Acceptance, Low mA SR, mA vs ma grid, 250-400 GeV, ggF prod</a> <li><a href=?table=table23>Acceptance, Low mA SR, mA vs ma grid, 400-550 GeV, ggF prod</a> <li><a href=?table=table24>Acceptance, Low mA SR, mA vs ma grid, >550 GeV, ggF prod</a> <li><a href=?table=table25>Efficiency, High mA SR, mA vs tanB grid, 400-750 GeV, bb prod</a> <li><a href=?table=table26>Efficiency, High mA SR, mA vs tanB grid, >750 GeV, bb prod</a> <li><a href=?table=table27>Efficiency, Low mA SR, mA vs tanB grid, 100-250 GeV, bb prod</a> <li><a href=?table=table28>Efficiency, Low mA SR, mA vs tanB grid, 250-400 GeV, bb prod</a> <li><a href=?table=table29>Efficiency, Low mA SR, mA vs tanB grid, 400-550 GeV, bb prod</a> <li><a href=?table=table30>Efficiency, Low mA SR, mA vs tanB grid, >550 GeV, bb prod</a> <li><a href=?table=table31>Efficiency, High mA SR, mA vs ma grid, 400-750 GeV, bb prod</a> <li><a href=?table=table32>Efficiency, High mA SR, mA vs ma grid, >750 GeV, bb prod</a> <li><a href=?table=table33>Efficiency, Low mA SR, mA vs ma grid, 100-250 GeV, bb prod</a> <li><a href=?table=table34>Efficiency, Low mA SR, mA vs ma grid, 250-400 GeV, bb prod</a> <li><a href=?table=table35>Efficiency, Low mA SR, mA vs ma grid, 400-550 GeV, bb prod</a> <li><a href=?table=table36>Efficiency, Low mA SR, mA vs ma grid, >550 GeV, bb prod</a> <li><a href=?table=table37>Efficiency, High mA SR, mA vs tanB grid, 400-750 GeV, ggF prod</a> <li><a href=?table=table38>Efficiency, High mA SR, mA vs tanB grid, >750 GeV, ggF prod</a> <li><a href=?table=table39>Efficiency, Low mA SR, mA vs tanB grid, 100-250 GeV, ggF prod</a> <li><a href=?table=table40>Efficiency, Low mA SR, mA vs tanB grid, 250-400 GeV, ggF prod</a> <li><a href=?table=table41>Efficiency, Low mA SR, mA vs tanB grid, 400-550 GeV, ggF prod</a> <li><a href=?table=table42>Efficiency, Low mA SR, mA vs tanB grid, >550 GeV, ggF prod</a> <li><a href=?table=table43>Efficiency, High mA SR, mA vs ma grid, 400-750 GeV, ggF prod</a> <li><a href=?table=table44>Efficiency, High mA SR, mA vs ma grid, >750 GeV, ggF prod</a> <li><a href=?table=table45>Efficiency, Low mA SR, mA vs ma grid, 100-250 GeV, ggF prod</a> <li><a href=?table=table46>Efficiency, Low mA SR, mA vs ma grid, 250-400 GeV, ggF prod</a> <li><a href=?table=table47>Efficiency, Low mA SR, mA vs ma grid, 400-550 GeV, ggF prod</a> <li><a href=?table=table48>Efficiency, Low mA SR, mA vs ma grid, >550 GeV, ggF prod</a> </ul>
Expected CLs values in the Low mA SR, mA vs tanB signal grid.
Observed CLs values in the Low mA SR, mA vs tanB signal grid.
A search for physics beyond the Standard Model inducing periodic signals in the dielectron and diphoton invariant mass spectra is presented using 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data collected by the ATLAS experiment at the LHC. Novel search techniques based on continuous wavelet transforms are used to infer the frequency of periodic signals from the invariant mass spectra and neural network classifiers are used to enhance the sensitivity to periodic resonances. In the absence of a signal, exclusion limits are placed at the 95% confidence level in the two-dimensional parameter space of the clockwork gravity model. Model-independent searches for deviations from the background-only hypothesis are also performed.
The observed exclusion limit at 95% CL for the clockwork gravity model projected in the $k–M_{5}$ parameter space for the $ee$ channel for the case with mass thresholds.
The median expected exclusion limit at 95% CL for the clockwork gravity model projected in the $k–M_{5}$ parameter space for the $ee$ channel for the case with mass thresholds.
The expected plus one standard deviation exclusion limit at 95% CL for the clockwork gravity model projected in the $k–M_{5}$ parameter space for the $ee$ channel for the case with mass thresholds.
A search for supersymmetry targeting the direct production of winos and higgsinos is conducted in final states with either two leptons ($e$ or $\mu$) with the same electric charge, or three leptons. The analysis uses 139 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13$ TeV collected with the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess over the Standard Model expectation is observed. Simplified and complete models with and without $R$-parity conservation are considered. In topologies with intermediate states including either $Wh$ or $WZ$ pairs, wino masses up to 525 GeV and 250 GeV are excluded, respectively, for a bino of vanishing mass. Higgsino masses smaller than 440 GeV are excluded in a natural $R$-parity-violating model with bilinear terms. Upper limits on the production cross section of generic events beyond the Standard Model as low as 40 ab are obtained in signal regions optimised for these models and also for an $R$-parity-violating scenario with baryon-number-violating higgsino decays into top quarks and jets. The analysis significantly improves sensitivity to supersymmetric models and other processes beyond the Standard Model that may contribute to the considered final states.
Observed exclusion limits at 95% CL for the WZ-mediated simplified model of wino $\tilde{\chi}^{\pm}_{1}/\tilde{\chi}^{0}_{2}$ production from Fig 13(b) and Fig 8(aux).
positive one $\sigma$ observed exclusion limits at 95% CL for the WZ-mediated simplified model of wino $\tilde{\chi}^{\pm}_{1}/\tilde{\chi}^{0}_{2}$ production from Fig 13(b) and Fig 8(aux).
negative $\sigma$ variation of observed exclusion limits at 95% CL for the WZ-mediated simplified model of wino $\tilde{\chi}^{\pm}_{1}/\tilde{\chi}^{0}_{2}$ production from Fig 13(b) and Fig 8(aux).
A search for a new pseudoscalar $a$-boson produced in events with a top-quark pair, where the $a$-boson decays into a pair of muons, is performed using $\sqrt{s} = 13$ TeV $pp$ collision data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of $139\, \mathrm{fb}^{-1}$. The search targets the final state where only one top quark decays to an electron or muon, resulting in a signature with three leptons $e\mu\mu$ and $\mu\mu\mu$. No significant excess of events above the Standard Model expectation is observed and upper limits are set on two signal models: $pp \rightarrow t\bar{t}a$ and $pp \rightarrow t\bar{t}$ with $t \rightarrow H^\pm b$, $H^\pm \rightarrow W^\pm a$, where $a\rightarrow\mu\mu$, in the mass ranges $15$ GeV $ < m_a < 72$ GeV and $120$ GeV $ \leq m_{H^{\pm}} \leq 160$ GeV.
Comparison between data and expected background for the on-$Z$-boson control region in the $e\mu\mu$ final state. The bins correspond to different jet and $b$-jet multiplicities. Rare background processes include $ZZ+$jets, $WWZ$, $WZZ$, $ZZZ$, and $t\bar{t}t\bar{t}$.
Comparison between data and expected background for the on-$Z$boson control region in the $\mu\mu\mu$ final state. The bins correspond to different jet and $b$-jet multiplicities. Rare background processes include $ZZ+$jets, $WWZ$, $WZZ$, $ZZZ$, and $t\bar{t}t\bar{t}$.
Di-muon mass distribution for the $e\mu\mu$ signal region for data and expected background. The expected signal distribution for $m_a = 35$ GeV is shown assuming $\sigma(t\bar{t}a)\times \text{Br}(a\rightarrow\mu\mu) = 4$ fb. Rare background processes include $ZZ+$jets, $WWZ$, $WZZ$, $ZZZ$, and $t\bar{t}t\bar{t}$.
A search is presented for displaced production of Higgs bosons or $Z$ bosons, originating from the decay of a neutral long-lived particle (LLP) and reconstructed in the decay modes $H\rightarrow \gamma\gamma$ and $Z\rightarrow ee$. The analysis uses the full Run 2 data set of proton$-$proton collisions delivered by the LHC at an energy of $\sqrt{s}=13$ TeV between 2015 and 2018 and recorded by the ATLAS detector, corresponding to an integrated luminosity of 139 fb$^{-1}$. Exploiting the capabilities of the ATLAS liquid argon calorimeter to precisely measure the arrival times and trajectories of electromagnetic objects, the analysis searches for the signature of pairs of photons or electrons which arise from a common displaced vertex and which arrive after some delay at the calorimeter. The results are interpreted in a gauge-mediated supersymmetry breaking model with pair-produced higgsinos that decay to LLPs, and each LLP subsequently decays into either a Higgs boson or a $Z$ boson. The final state includes at least two particles that escape direct detection, giving rise to missing transverse momentum. No significant excess is observed above the background expectation. The results are used to set upper limits on the cross section for higgsino pair production, up to a $\tilde\chi^0_1$ mass of 369 (704) GeV for decays with 100% branching ratio of $\tilde\chi^0_1$ to Higgs ($Z$) bosons for a $\tilde\chi^0_1$ lifetime of 2 ns. A model-independent limit is also set on the production of pairs of photons or electrons with a significant delay in arrival at the calorimeter.
Average timing distributions for SR data and the estimated background as determined by the background-only fit, in each of the five exclusive $\rho$ categories. For comparison, the expected timing shapes for a few different signal models are superimposed, with each model labeled by the values of the $\tilde\chi^0_1$ mass and lifetime, as well as decay mode. To provide some indication of the variations in signal yield and shape, three signal models are shown for each of the $\tilde\chi^0_1$ decay modes, namely $\tilde\chi^0_1$ $\rightarrow$ $H \tilde G$ and $\tilde\chi^0_1$ $\rightarrow$ $Z \tilde G$. The models shown include a rather low $\tilde\chi^0_1$ mass value of 135 GeV for lifetimes of either 2 ns or 10 ns, and a higher $\tilde\chi^0_1$ mass value which is near the 95% CL exclusion limit for each decay mode for a lifetime of 2 ns. Each signal model is shown with the signal normalization corresponding to a BR value of unity for the decay mode in question.
Average timing distributions for SR data and the estimated background as determined by the background-only fit, in each of the five exclusive $\rho$ categories. For comparison, the expected timing shapes for a few different signal models are superimposed, with each model labeled by the values of the $\tilde\chi^0_1$ mass and lifetime, as well as decay mode. To provide some indication of the variations in signal yield and shape, three signal models are shown for each of the $\tilde\chi^0_1$ decay modes, namely $\tilde\chi^0_1$ $\rightarrow$ $H \tilde G$ and $\tilde\chi^0_1$ $\rightarrow$ $Z \tilde G$. The models shown include a rather low $\tilde\chi^0_1$ mass value of 135 GeV for lifetimes of either 2 ns or 10 ns, and a higher $\tilde\chi^0_1$ mass value which is near the 95% CL exclusion limit for each decay mode for a lifetime of 2 ns. Each signal model is shown with the signal normalization corresponding to a BR value of unity for the decay mode in question.
Average timing distributions for SR data and the estimated background as determined by the background-only fit, in each of the five exclusive $\rho$ categories. For comparison, the expected timing shapes for a few different signal models are superimposed, with each model labeled by the values of the $\tilde\chi^0_1$ mass and lifetime, as well as decay mode. To provide some indication of the variations in signal yield and shape, three signal models are shown for each of the $\tilde\chi^0_1$ decay modes, namely $\tilde\chi^0_1$ $\rightarrow$ $H \tilde G$ and $\tilde\chi^0_1$ $\rightarrow$ $Z \tilde G$. The models shown include a rather low $\tilde\chi^0_1$ mass value of 135 GeV for lifetimes of either 2 ns or 10 ns, and a higher $\tilde\chi^0_1$ mass value which is near the 95% CL exclusion limit for each decay mode for a lifetime of 2 ns. Each signal model is shown with the signal normalization corresponding to a BR value of unity for the decay mode in question.
A search for high-mass charged and neutral bosons decaying to $W\gamma$ and $Z\gamma$ final states is presented in this paper. The analysis uses a data sample of $\sqrt{s} = 13$ TeV proton-proton collisions with an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector during LHC Run 2 operation. The sensitivity of the search is determined using models of the production and decay of spin-1 charged bosons and spin-0/2 neutral bosons. The range of resonance masses explored extends from 1.0 TeV to 6.8 TeV. At these high resonance masses, it is beneficial to target the hadronic decays of the $W$ and $Z$ bosons because of their large branching fractions. The decay products of the high-momentum $W/Z$ bosons are strongly collimated and boosted-boson tagging techniques are employed to improve the sensitivity. No evidence of a signal above the Standard Model backgrounds is observed, and upper limits on the production cross-sections of these bosons times their branching fractions to $W\gamma$ and $Z\gamma$ are derived for various boson production models.
The jet mass distribution of large-$R$ jets originating from the hadronic decay of $W$ and $Z$ bosons produced from the decay of BSM bosons with mass $m_X = 1000$ GeV. The decays simulated are for the production models $q\bar{q}' \to X^{\pm} \to W^{\pm}\gamma$ with a spin-1 resonance $X^{\pm}$ and $gg\to X^0 \to Z\gamma$ with a spin-0 resonance $X^{0}$.
The jet mass distribution of large-$R$ jets originating from the hadronic decay of $W$ and $Z$ bosons produced from the decay of BSM bosons with mass $m_X = 4000$ GeV. The decays simulated are for the production models $q\bar{q'}\to X^{\pm} \to W^{\pm}\gamma$ with a spin-1 resonance $X^{\pm}$ and $gg\to X^0 \to Z\gamma$ with a spin-0 resonance $X^{0}$.
Total efficiencies for the selection of signal events after categorization and application of the tighter photon $E_{\mathrm{T}}^{\gamma}$ selection used to optimize the signal significance spin-0 $gg\to X^0 \to Z\gamma$. In addition to the total efficiency, contributions to the signal selection from each of the separate event categories are shown. The efficiencies calculated from MC samples with $W/Z$ hadronic decays are shown as the points on each curve. The line presents interpolated results.
A search for forward proton scattering in association with light-by-light scattering mediated by an axion-like particle is presented, using the ATLAS Forward Proton spectrometer to detect scattered protons and the central ATLAS detector to detect pairs of outgoing photons. Proton-proton collision data recorded in 2017 at a centre-of-mass energy of $\sqrt{s} = 13$ TeV were analysed, corresponding to an integrated luminosity of 14.6 fb$^{-1}$. A total of 441 candidate signal events were selected. A search was made for a narrow resonance in the diphoton mass distribution, corresponding to an axion-like particle (ALP) with mass in the range 150-1600 GeV. No excess is observed above a smooth background. Upper limits on the production cross section of a narrow resonance are set as a function of the mass, and are interpreted as upper limits on the ALP production coupling constant, assuming 100% decay branching ratio into a photon pair. The inferred upper limit on the coupling constant is in the range 0.04-0.09 TeV$^{-1}$ at 95%confidence level.
Signal selection efficiency as a function of ALP mass $m_{\textrm{X}}$ for the exclusive (EL), single-dissociative (SD), and double-dissociative (DD) processes. The ratio of the number of selected events to the number of generated MC events is given (black points) and is parameterised by an analytic function (red solid line). The linear (black dashed line) and cubic (blue chain line) interpolations of the black points are used to derive the envelopes (cyan filled region) which are regarded as systematic uncertainties.
The diphoton mass distribution of the mixed-data sample (black points).
The $(\xi_{\gamma\gamma}^{+},\xi_{\gamma\gamma}^{-})$ distribution of the selected data candidates after the full event selection in $m_{\gamma\gamma}$ in [150,1600] GeV with $m_{\gamma\gamma}$ contours (blue) and $y_{\gamma\gamma}$ contours (black). The range of $\xi_{\gamma\gamma}$ in which forward-proton matching is possible, $[0.035-\xi_{\textrm{th}}, 0.08+\xi_{\textrm{th}} ]$, for events that pass the matching requirement to the A or C side as indicated. No event passed the matching requirement for both the A-side and C-side.
A search for heavy right-handed Majorana or Dirac neutrinos $N_{\mathrm{R}}$ and heavy right-handed gauge bosons $W_{\mathrm{R}}$ is performed in events with energetic electrons or muons, with the same or opposite electric charge, and energetic jets. The search is carried out separately for topologies of clearly separated final-state products (``resolved'' channel) and topologies with boosted final states with hadronic and/or leptonic products partially overlapping and reconstructed as a large-radius jet (``boosted'' channel). The events are selected from $pp$ collision data at the LHC with an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector at $\sqrt{s}$ = 13 TeV. No significant deviations from the Standard Model predictions are observed. The results are interpreted within the theoretical framework of a left-right symmetric model, and lower limits are set on masses in the heavy right-handed $W_{\mathrm{R}}$ boson and $N_{\mathrm{R}}$ plane. The excluded region extends to about $m(W_{\mathrm{R}}) = 6.4$ TeV for both Majorana and Dirac $N_{\mathrm{R}}$ neutrinos at $m(N_{\mathrm{R}})<1$ TeV. $N_{\mathrm{R}}$ with masses of less than 3.5 (3.6) TeV are excluded in the electron (muon) channel at $m(W_{\mathrm{R}})=4.8$ TeV for the Majorana neutrinos, and limits of $m(N_{\mathrm{R}})$ up to 3.6 TeV for $m(W_{\mathrm{R}}) = 5.2$ (5.0) TeV in the electron (muon) channel are set for the Dirac neutrinos. These constitute the most stringent exclusion limits to date for the model considered.
Observed 95% CL exclusion contours in the $(m(W_{R}), m(N_{R}))$ plane in the electron channel for boosted.
Expected 95% CL exclusion contours in the $(m(W_{R}), m(N_{R}))$ plane in the electron channel for boosted.
Observed 95% CL exclusion contours in the $(m(W_{R}), m(N_{R}))$ plane in the muon channel for boosted.
Differential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs ($t\bar{t}$) are measured using the full LHC Run 2 data sample collected with the ATLAS detector. The data were collected at a $pp$ collision energy of $\sqrt{s}=13$ TeV and correspond to an integrated luminosity of 140 fb$^{-1}$. The measurements use events containing an oppositely charged $e\mu$ pair and $b$-tagged jets. The results are compared with predictions from several Monte Carlo generators. While no prediction is found to be consistent with all distributions, a better agreement with measurements of the lepton $p_{\text{T}}$ distributions is obtained by reweighting the $t\bar{t}$ sample so as to reproduce the top-quark $p_{\text{T}}$ distribution from an NNLO calculation. The inclusive top-quark pair production cross-section is measured as well, both in a fiducial region and in the full phase-space. The total inclusive cross-section is found to be \[ \sigma_{t\bar{t}} = 829 \pm 1\;(\textrm{stat}) \pm 13\;(\textrm{syst}) \pm 8\;(\textrm{lumi}) \pm 2\; (\textrm{beam})\ \textrm{pb}, \] where the uncertainties are due to statistics, systematic effects, the integrated luminosity and the beam energy. This is in excellent agreement with the theoretical expectation.
Definition of the fiducial phase space with the lepton candidate, electron $e$ and muon $\mu$, and jets.
Definition of the fiducial phase space with the lepton candidate, electron $e$ and muon $\mu$, and jets.
Definition of the fiducial phase space with the lepton candidate, electron $e$ and muon $\mu$, and jets.
A search is reported for excited $\tau$-leptons and leptoquarks in events with two hadronically decaying $\tau$-leptons and two or more jets. The search uses proton-proton (pp) collision data at $\sqrt{s} = 13$ TeV recorded by the ATLAS experiment during the Run 2 of the Large Hadron Collider in 2015-2018. The total integrated luminosity is 139 fb$^{-1}$. The excited $\tau$-lepton is assumed to be produced and to decay via a four-fermion contact interaction into an ordinary $\tau$-lepton and a quark-antiquark pair. The leptoquarks are assumed to be produced in pairs via the strong interaction, and each leptoquark is assumed to couple to a charm or lighter quark and a $\tau$-lepton. No excess over the background prediction is observed. Excited $\tau$-leptons with masses below 2.8 TeV are excluded at 95% CL in scenarios with the contact interaction scale $\Lambda$ set to 10 TeV. At the extreme limit of model validity where $\Lambda$ is set equal to the excited $\tau$-lepton mass, excited $\tau$-leptons with masses below 4.6 TeV are excluded. Leptoquarks with masses below 1.3 TeV are excluded at 95% CL if their branching ratio to a charm quark and a $\tau$-lepton equals 1. The analysis does not exploit flavour-tagging in the signal region.
Observed and expected upper 95% CL limit on the $\tau^\ast$ production cross-section as a function of $m_{\tau^\ast}$ for a fixed value of the contact interaction scale, $\Lambda = 10$ TeV.
Observed and expected lower 95% CL limit on the contact interaction scale $\Lambda$ as a function of $m_{\tau^\ast}$.
Observed and expected upper 95% CL limit on the LQ production cross-section as a function of $m_\mathrm{LQ}$. The LQ couples to a tau lepton and a c-quark. The limits are also valid for scenarios in which the LQ couples to lighter quarks.
A search for pair-produced scalar or vector leptoquarks decaying into a $b$-quark and a $\tau$-lepton is presented using the full LHC Run 2 (2015-2018) data sample of 139 fb$^{-1}$ collected with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} =13$ TeV. Events in which at least one $\tau$-lepton decays hadronically are considered, and multivariate discriminants are used to extract the signals. No significant deviations from the Standard Model expectation are observed and 95% confidence-level upper limits on the production cross-section are derived as a function of leptoquark mass and branching ratio $B$ into a $\tau$-lepton and $b$-quark. For scalar leptoquarks, masses below 1460 GeV are excluded assuming $B=100$%, while for vector leptoquarks the corresponding limit is 1650 GeV (1910 GeV) in the minimal-coupling (Yang-Mills) scenario.
Acceptance $\times$ efficiency for the $\tau_\text{lep}\tau_\text{had}$ signal region assuming $\beta$ = 0.5 as a function of m$_\text{LQ}$.
Acceptance $\times$ efficiency for the $\tau_\text{had}\tau_\text{had}$ signal region assuming $\beta$ = 0.5 as a function of m$_\text{LQ}$.
The observed and expected 95% CL upper limits on the scalar LQ pair production cross-sections assuming B = 1 as a function of m$_\text{LQ}$.
Forum