A search for non-resonant Higgs boson pair production, as predicted by the Standard Model, is presented, where one of the Higgs bosons decays via the $H\rightarrow bb$ channel and the other via one of the $H \rightarrow WW^*/ZZ^*/\tau\tau$ channels. The analysis selection requires events to have at least two $b$-tagged jets and exactly two leptons (electrons or muons) with opposite electric charge in the final state. Candidate events consistent with Higgs boson pair production are selected using a multi-class neural network discriminant. The analysis uses 139 fb$^{-1}$ of $pp$ collision data recorded at a centre-of-mass energy of 13 TeV, by the ATLAS detector at the Large Hadron Collider. An observed (expected) upper limit of 1.2 ($0.9^{+0.4}_{-0.3}$) pb is set on the non-resonant Higgs boson pair production cross-section at 95% confidence level, which is equivalent to 40 ($29^{+14}_{-9}$) times the value predicted in the Standard Model.
Reconstruction-level analysis selection efficiency for the $HH \rightarrow bbWW^* \rightarrow bbl\nu l\nu$ signal process as a function of the truth-level $HH$ invariant mass, $m_{HH}$. Each color indicates an additional selection applied sequentially and in the order indicated in the legend with respect to the starting sample of events satisfying the analysis preselection requirements and having at least two $b$-tagged jets. In the legend, ``Trigger'' refers to enforcing the analysis' trigger requirements. For reference, overlaid in grey colour and with arbitrary normalisation is the truth level $m_{HH}$ distribution for events having only the preselection criteria applied. The total efficiency for the tightest selection that is shown (red line), which has selection requirements similar to those of the analysis' signal regions SR-SF and SR-DF, is $7.1\%$.
Expected and observed $95\%$ CL limits on the cross-section of ggF non-resonant Higgs boson pair production as a function of the Higgs boson self-coupling modifier, $\kappa_{\lambda} = \lambda_{HHH} / \lambda_{HHH}^{\textit{SM}}$. The $\pm 1 \sigma$ and $\pm 2 \sigma$ variations about the expected limit, due to statistical and systematic uncertainties, are also shown. The method used for producing estimates of $HH$ production at non-SM values of $\kappa_{\lambda}$ is fully described in arXiv:1906.02025. The theory prediction curve represents the scenario where all parameters and couplings are set to their SM values except for $\kappa_{\lambda}$, also described in arXiv:1906.02025. The uncertainty band on the theory prediction indicates the theoretical uncertainty of this prediction. No additional analysis optimisation relative to that appearing in the main body of the analysis is performed to become particularly sensitive to non-SM values of $\kappa_{\lambda}$. The vertical dashed line indicates the SM scenario with $\kappa_{\lambda} = 1$.
Heavy neutrinos were sought in pion decays $\pi^+ \rightarrow \mu^+ \nu$ by examining the observed muon energy spectrum for extra peaks in addition to the expected peak for a massless neutrino. No evidence for heavy neutrinos was observed. Upper limits were set on the neutrino mixing matrix $|U_{\mu i}|^2$ in the neutrino mass region of 15.7--33.8 MeV/c$^2$, improving on previous results by an order of magnitude.
90% C.L. upper limits in Tmu<1.2MeV
90% C.L. upper limits in Tmu>1.2MeV
A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, $\varDelta \phi _{12}$ , is presented. The measurement considers events where the two leading jets are nearly collinear (“back-to-back”) in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of $13\,\text {Te}\text {V} $ and corresponding to an integrated luminosity of $35.9{\,\text {fb}^{-1}} $ are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region $177^\circ< \varDelta \phi _{12} < 180^\circ $ . The 2- and 3-jet measurements are not simultaneously described by any of models.
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This paper presents a measurement of jet fragmentation functions in 0.49 nb−1 of Pb+Pb collisions and 25 pb−1 of pp collisions at sNN=5.02 TeV collected in 2015 with the ATLAS detector at the LHC. These measurements provide insight into the jet quenching process in the quark-gluon plasma created in the aftermath of ultrarelativistic collisions between two nuclei. The modifications to the jet fragmentation functions are quantified by dividing the measurements in Pb+Pb collisions by baseline measurements in pp collisions. This ratio is studied as a function of the transverse momentum of the jet, the jet rapidity, and the centrality of the collision. In both collision systems, the jet fragmentation functions are measured for jets with transverse momentum between 126 and 398 GeV and with an absolute value of jet rapidity less than 2.1. An enhancement of particles carrying a small fraction of the jet momentum is observed, which increases with centrality and with increasing jet transverse momentum. Yields of particles carrying a very large fraction of the jet momentum are also observed to be enhanced. Between these two enhancements of the fragmentation functions a suppression of particles carrying an intermediate fraction of the jet momentum is observed in Pb+Pb collisions. A small dependence of the modifications on jet rapidity is observed.
The D(z) distributions in different centrality intervals in PbPb and in pp for 126.00 < pTjet < 158.49 and 0.0 < eta < 0.3.
The D(pT) distributions in different centrality intervals in PbPb and in pp for 126.00 < pTjet < 158.49 and 0.0 < eta < 0.3.
The ratio of the D(z) in different centrality intervals in PbPb and in pp for 126.00 < pTjet < 158.49 and 0.0 < eta < 0.3.
A search is presented for a Higgs boson that is produced in association with a Z boson and that decays to an undetected particle together with an isolated photon. The search is performed by the CMS Collaboration at the Large Hadron Collider using a data set corresponding to an integrated luminosity of 137 fb$^{-1}$ recorded at a center-of-mass energy of 13 TeV. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for associated Higgs and Z boson production and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a mass of 125 GeV, assuming the standard model production cross section, this corresponds to an observed (expected) upper limit on this branching fraction of 4.6 (3.6)% at 95% confidence level. These are the first limits on Higgs boson decays to final states that include an undetected massless dark photon.
Observed yields, background estimates after the fit to data, and signal predictions after the event selection in the signal region. The signal size corresponds to $0.1 \sigma_{\mathrm{\mathrm{ZH}}}$ for all three $m_{\mathrm{\mathrm{H}}}$ values shown. The combined statistical and systematic uncertainties are reported.
Covariance matrix for all bins used in the analysis. There are 45 bins in total, 15 for every data-taking year. For every year, the first bin corresponds to events in the $\mathrm{e}\mu$ control region, the following five bins correspond to events with $|\eta^\gamma|< 1$ in the signal region, the next five bins correspond to events with $|\eta^\gamma|> 1$ in the signal region, the next two bins correspond to events in the WZ control region, and finally the last two bins correspond to events in the ZZ control region.
Electron reconstruction, identification, and isolation efficiency as a function of $|\eta|$ and $\mathrm{p_\mathrm{T}}$.
A search for dark matter produced in association with top quarks in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The data set used corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded with the CMS detector at the LHC. Whereas previous searches for neutral scalar or pseudoscalar mediators considered dark matter production in association with a top quark pair only, this analysis also includes production modes with a single top quark. The results are derived from the combination of multiple selection categories that are defined to target either the single top quark or the top quark pair signature. No significant deviations with respect to the standard model predictions are observed. The results are interpreted in the context of a simplified model in which a scalar or pseudoscalar mediator particle couples to a top quark and subsequently decays into dark matter particles. Scalar and pseudoscalar mediator particles with masses below 290 and 300 GeV, respectively, are excluded at 95 % confidence level, assuming a dark matter particle mass of 1 GeV and mediator couplings to fermions and dark matter particles equal to unity.
Background-only post-fit $p_{T}^{miss}$ distributions for the SRs of the AH selection. The total theory signal (t/t+DM and tt+DM summed together) is presented by the red solid lines for a scalar mediator mass of 100 GeV. The last bin contains overflow events.
Background-only post-fit $p_{T}^{miss}$ distributions for the SRs of the SL selection. The total theory signal (t/t+DM and tt+DM summed together) is presented by the red solid lines for a scalar mediator mass of 100 GeV. The last bin contains overflow events.
Background-only post-fit $p_{T}^{miss}$ distributions for the SRs of the SL selection. The total theory signal (t/t+DM and tt+DM summed together) is presented by the red solid lines for a scalar mediator mass of 100 GeV. The last bin contains overflow events.
A search for supersymmetric partners of gluons and quarks is presented, involving signatures with jets and either two isolated leptons (electrons or muons) with the same electric charge, or at least three isolated leptons. A data sample of proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to a total integrated luminosity of 139 fb$^{-1}$, is used for the search. No significant excess over the Standard Model expectation is observed. The results are interpreted in simplified supersymmetric models featuring both R-parity conservation and R-parity violation, raising the exclusion limits beyond those of previous ATLAS searches to 1600 GeV for gluino masses and 750 GeV for bottom and top squark masses in these scenarios.
Best observed 95% CL exclusion contours selected from Rpc2L1b and Rpc2L2b on the lightest bottom squark and lightest neutralino masses in a SUSY scenario where pairs of bottom-antibottom squarks are produced and decay into the lightest neutralino via a chargino, $\tilde b^{}_{1}\to t\tilde{\chi}_1^-$ followed by $\tilde{\chi}_1^\pm\to W^\pm\tilde{\chi}_1^0$.
Number of signal events expected for 139 fb$^{-1}$ at different stages of the event selection for the signal region Rpc2L0b, in a SUSY scenario where gluinos are produced in pairs and decay into the lightest neutralino via a two-steps cascade, $\tilde g\to q\bar{q}^{'}\tilde{\chi}_1^\pm$ followed by $\tilde{\chi}_1^\pm\to W^\pm\tilde{\chi}_2^0$ and $\tilde{\chi}_2^0\to Z\tilde{\chi}_1^0$. The masses of the superpartners involved in the process are set to $m(\tilde g)$ = 1600 GeV, $m(\tilde \chi_1^\pm)$ = 1200 GeV, $m(\tilde \chi_2^0)$ = 1000 GeV and $m(\tilde \chi_1^0)$ = 800 GeV. Only statistical uncertainties are shown.
Number of signal events expected for 139 fb$^{-1}$ at different stages of the event selection for the signal region Rpc2L1b, in a SUSY scenario where pairs of bottom-antibottom squarks are produced and decay into the lightest neutralino via a chargino, $\tilde b^{}_{1}\to t\tilde{\chi}_1^-$ followed by $\tilde{\chi}_1^\pm\to W^\pm\tilde{\chi}_1^0$. The masses of the superpartners involved in the process are set to $m(\tilde{b}^{}_1)$ = 850 GeV, $m(\tilde \chi_1^\pm)$ = 500 GeV and $m(\tilde \chi_1^0)$ = 400 GeV. Only statistical uncertainties are shown.
A measurement of the differential branching fraction of the decay B$^{0}$ → K$^{∗}$(892)$^{0}$ μ$^{+}$ μ$^{−}$ is presented together with a determination of the S-wave fraction of the K$^{+}$ π$^{−}$ system in the decay B$^{0}$ → K$^{+}$π$^{−}$ μ$^{+}$ μ$^{−}$. The analysis is based on pp-collision data corresponding to an integrated luminosity of 3 fb$^{−1}$ collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q$^{2}$. Precise theoretical predictions for the differential branching fraction of B$^{0}$ → K$^{∗}$(892)$^{0}$ μ$^{+}$ μ$^{−}$ decays are available for the q$^{2}$ region 1.1 < q$^{2}$ < 6.0 GeV$^{2}$ /c$^{4}$. In this q$^{2}$ region, for the K$^{+}$π$^{−}$ invariant mass range 796 < m$_{Kπ}$ < 996 MeV/c$^{2}$, the S-wave fraction of the K$^{+}$π$^{−}$ system in B$^{0}$ → K$^{+}$π$^{−}$ μ$^{+}$ μ$^{−}$ decays is found to be $ {F}_{\mathrm{S}}=0.101\pm 0.017\left(\mathrm{stat}\right)\pm 0.009\left(\mathrm{syst}\right), $ and the differential branching fraction of B$^{0}$ → K$^{∗}$(892)$^{0}$ μ$^{+}$ μ$^{−}$ decays is determined to be $ \mathrm{d}\mathrm{\mathcal{B}}/\mathrm{d}{q}^2=\left(0.{392}_{-0.019}^{+0.020}\left(\mathrm{stat}\right)\pm 0.010\left(\mathrm{syst}\right)\pm 0.027\left(\mathrm{norm}\right)\right)\times 1{0}^{-7}{c}^4/{\mathrm{GeV}}^2. $
S-wave fraction ($F_{\rm S}$) in bins of $q^2$ for two $m_{K\pi}$ regions. The first uncertainty is statistical and the second systematic.
Differential branching fraction of $B^0 \to K^*(892)^0 \mu^+ \mu^-$ decays in bins of $q^2$. The first uncertainty is statistical, the second systematic and the third due to the uncertainty on the $B^0 \to J/\psi K^{*0}$ and $J/\psi \to \mu^+ \mu^-$ branching fractions.
Measurements of the differential cross section for the Drell-Yan process, based on proton-proton collision data at a centre-of-mass energy of 13 TeV, collected by the CMS experiment, are presented. The data correspond to an integrated luminosity of 2.8 (2.3) fb$^{-1}$ in the dimuon (dielectron) channel. The total and fiducial cross section measurements are presented as a function of dilepton invariant mass in the range 15 to 3000 GeV, and compared with the perturbative predictions of the standard model. The measured differential cross sections are in good agreement with the theoretical calculations.
Summary of the systematic uncertainties (%) for the $ d\sigma / d{m}$ (pb/GeV) measurement in the dimuon channel. The column labelled "Total" corresponds to the quadratic sum of all the experimental sources, except for that Acceptance+PDF.
Summary of the systematic uncertainties (%) for the $ d\sigma / d{m}$ (pb/GeV) measurement in the dielectron channel. The column labelled "Total" corresponds to the quadratic sum of all the experimental sources, except for that Acceptance+PDF.
Summary of the measured values of $ d\sigma / d{m}$ (pb/GeV) in the dimuon channel with the statistical ($\delta_{\text{stat}}$), experimental ($\delta_{\text{exp}}$) and theoretical ($\delta_{\text{theo}}$) uncertainties, respectively. Here, $\delta_{\text{tot}}$ is the quadratic sum of the three components.
A search for supersymmetric particles produced in the vector boson fusion topology in proton-proton collisions is presented. The search targets final states with one or zero leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 35.9 fb$^{−1}$ of proton-proton collisions at $ \sqrt{s} $ = 13 TeV collected in 2016 with the CMS detector at the LHC. The observed dijet invariant mass and lepton-neutrino transverse mass spectra are found to be consistent with the standard model predictions. Upper limits are set on the cross sections for chargino $ \left({\tilde{\upchi}}_1^{\pm}\right) $ and neutralino $ \left({\tilde{\upchi}}_2^0\right) $ production with two associated jets. For a compressed mass spectrum scenario in which the $ {\tilde{\upchi}}_1^{\pm } $ and $ {\tilde{\upchi}}_2^0 $ decays proceed via a light slepton and the mass difference between the lightest neutralino $ {\tilde{\upchi}}_1^0 $ and the mass-degenerate particles $ {\tilde{\upchi}}_1^{\pm } $ and $ {\tilde{\upchi}}_2^0 $ is 1 (30) GeV, the most stringent lower limit to date of 112 (215) GeV is set on the mass of these latter two particles.
Combined 95% CL expected upper limit on the signal cross section as a function of $m_{\tilde{\chi}_{2}^{0}}=m_{\tilde{\chi}_{1}^{\pm}}$ for a $\Delta m=1$ GeV mass gap between the chargino and the lightest neutralino in the $W Z$ model.
Combined 95% CL expected upper limit on the signal cross section as a function of $m_{\tilde{\chi}_{2}^{0}}=m_{\tilde{\chi}_{1}^{\pm}}$ for a $\Delta m=50$ GeV mass gap between the chargino and the lightest neutralino in the $W Z$ model.
Combined 95% CL observed upper limit on the signal cross section as a function of $m_{\tilde{\chi}_{2}^{0}}=m_{\tilde{\chi}_{1}^{\pm}}$ for a $\Delta m=1$ GeV mass gap between the chargino and the lightest neutralino in the $W Z$ model.