Measurements of the total and differential fiducial cross sections for the Z boson decaying into two neutrinos are presented at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data were collected by the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb$^{-1}$. In these measurements, events are selected containing an imbalance in transverse momentum and one or more energetic jets. The fiducial differential cross section is measured as a function of the Z boson transverse momentum. The results are combined with a previous measurement of charged-lepton decays of the Z boson.
The measured and predicted inclusive fiducial cross sections in fb. The experimental measurement includes both statistical and systematics uncertainties. The theoretical prediction includes both the QCD scale and PDF uncertainties.
Experimental uncertainties affecting transfer factors in the analysis that is used to estimate the W background in the signal region (SR). The number of W boson events are denoted as $W_{SR}$ for the SR and in analogy as $W_{\mu\nu}$ ($W_{e\nu}$) for the single-muon (single-electron) control region (CR).
Uncertainties assigned to the simulation based processes in SR and CRs.
The observation of forward proton scattering in association with lepton pairs ($e^+e^-+p$ or $\mu^+\mu^-+p$) produced via photon fusion is presented. The scattered proton is detected by the ATLAS Forward Proton spectrometer while the leptons are reconstructed by the central ATLAS detector. Proton-proton collision data recorded in 2017 at a center-of-mass energy of $\sqrt{s} = 13$ TeV are analyzed, corresponding to an integrated luminosity of 14.6 fb$^{-1}$. A total of 57 (123) candidates in the $ee+p$ ($\mu\mu+p$) final state are selected, allowing the background-only hypothesis to be rejected with a significance exceeding five standard deviations in each channel. Proton-tagging techniques are introduced for cross-section measurements in the fiducial detector acceptance, corresponding to $\sigma_{ee+p}$ = 11.0 $\pm$ 2.6 (stat.) $\pm$ 1.2 (syst.) $\pm$ 0.3 (lumi.) fb and $\sigma_{\mu\mu+p}$ = 7.2 $\pm$ 1.6 (stat.) $\pm$ 0.9 (syst.) $\pm$ 0.2 (lumi.) fb in the dielectron and dimuon channel, respectively.
The measured fiducial cross sections. The first systematic uncertainty is the combined systematic uncertainty excluding luminosity, the second is the luminosity
A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak W$\gamma$jj production in a restricted fiducial region is measured as 20.4 $\pm$ 4.5 fb and the total cross section for W$\gamma$ production in association with 2 jets in the same fiducial region is 108 $\pm$ 16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators.
The measured EW W$\gamma$jj fiducial cross section. The uncertainty is the combined stastical uncertianty and the systematic uncertainty including experimental and theortical sources. The EW W$\gamma$jj is produced using MadGraph5_aMC@NLO v2.6.0 at LO. Within the acceptance, the theoretical cross section is 17.0 fb.
The measured W$\gamma$jj cross section, combining the EW and QCD-induced production mechanisms. The uncertainty is the combined stastical uncertianty and the systematic uncertainty including experimental and theortical sources. The QCD W$\gamma$jj is produced using MadGraph5_aMC@NLO v2.4.2 at NLO in QCD. Within the acceptance, the theoretical cross section of QCD W$\gamma$jj is 72.7 fb. The EW W$\gamma$jj is produced using MadGraph5_aMC@NLO v2.6.0 at LO. Within the acceptance, the theoretical cross section of EW W$\gamma$jj is 17.0 fb. The total EW+QCD W$\gamma$ jj cross section is the sum of the two processes.
Constraints on dimension-8 effective field theory operators.
Evidence is presented for the electroweak (EW) production of two jets (jj) in association with two Z bosons and constraints on anomalous quartic gauge couplings are set. The analysis is based on a data sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV collected with the CMS detector in 2016-2018, and corresponding to an integrated luminosity of 137 fb$^{-1}$. The search is performed in the fully leptonic final state ZZ $\to$ $\ell\ell\ell'\ell'$, where $\ell,\ell' = $ e, $\mu$. The EW production of two jets in association with two Z bosons is measured with an observed (expected) significance of 4.0 (3.5) standard deviations. The cross sections for the EW production are measured in three fiducial volumes and the result is $\sigma_{\mathrm{EW}}$(pp $\to$ ZZjj $\to$ $\ell\ell\ell'\ell'$jj) = 0.33 $^{+0.11}_{-0.10}$ (stat) $^{+0.04}_{-0.03}$ (syst) fb in the most inclusive volume, in agreement with the standard model prediction of 0.275 $\pm$ 0.021 fb. Measurements of total cross sections for jj production in association with two Z bosons are also reported. Limits on anomalous quartic gauge couplings are derived in terms of the effective field theory operators T0, T1, T2, T8, and T9.
Data from paper Table 3. Measured and expected fiducial cross-sections in the ZZjj inclusive fiducial region.
Data from paper Table 3. Measured and expected fiducial cross-sections in the VBS-enriched loose fiducial region.
Data from paper Table 3. Measured and expected fiducial cross-sections in the VBS-enriched tight fiducial region.
This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at $\sqrt{s}=13$ TeV collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 139 fb$^{-1}$. The analysis is performed by reconstructing hadronically decaying Higgs boson $(H\to b\bar{b})$ candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two $b$-quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-section times branching fraction for narrow spin-1 resonances decaying into a Higgs boson and a photon in the resonance mass range from 0.7 to 4 TeV, cross-sections times branching fraction are excluded between 11.6 fb and 0.11 fb at a 95% confidence level.
Data distribution of the reconstructed $m_{J\gamma}$ and background only fitting in the single-b-tagged category. Background and signal fit functions are provided in Table 3. Background event yields are calculated using the fitted background function.
Data distribution of the reconstructed $m_{J\gamma}$ and background only fitting in the double-b-tagged category. Background and signal fit functions are provided in Table 3. Background event yields are calculated using the fitted background function.
Background and signal functions, with their fit parameters. For the background function, the parameters are fitted from the data distribution. The "Yield" is the total number of events in data in the single-b-tagged or double-b-tagged fitting range. For the single-b-tagged category, the fitting range is [1400GeV, 4200GeV], and for the double-b-tagged category, it is [600GeV, 4200GeV]. The background event yields per bin in Table 1 and Table 2 are calculated using the data yield multiplied by the integral of the normalized background function in that bin. For the signal function, the value for the parameters are from parametrisation studies and CB stands for a Crystal-Ball function. Signal distributions in Figure 1a and Figure 1b are normalized to an arbitrary yield, for illustration purpose.
A search is presented for four-top-quark production using an integrated luminosity of 139 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. Events are selected if they contain a same-sign lepton pair or at least three leptons (electrons or muons). Jet multiplicity, jet flavour and event kinematics are used to separate signal from the background through a multivariate discriminant, and dedicated control regions are used to constrain the dominant backgrounds. The four-top-quark production cross section is measured to be 24$^{+7}_{-6}$ fb. This corresponds to an observed (expected) significance with respect to the background-only hypothesis of 4.3 (2.4) standard deviations and provides evidence for this process.
The results of fitted inclusive ${t\bar{t}t\bar{t}}$ cross-section
The results of the fitted signal strength $\mu$
List of the uncertainties in the signal strength $\mu$, grouped in categories. The quoted values are obtained by repeating the fit, fixing a set of nuisance parameters of the sources corresponding to the considered category, and subtracting in quadrature the resulting uncertainty from the total uncertainty of the nominal fit presented in the last line. The total uncertainty is different from the sum in quadrature of the components due to correlations between nuisance parameters.
A search for heavy resonances decaying into a $W$ or $Z$ boson and a Higgs boson produced in proton$-$proton collisions at the Large Hadron Collider at $\sqrt{s} = 13$ TeV is presented. The analysis utilizes the dominant $W \to q \bar{q}^\prime$ or $Z \to q \bar{q}$ and $H \to b \bar{b}$ decays with substructure techniques applied to large-radius jets. A sample corresponding to an integrated luminosity of 139 fb$^{-1}$ collected with the ATLAS detector is analyzed and no significant excess of data is observed over the background prediction. The results are interpreted in the context of the Heavy Vector Triplet model with spin-1 $W^\prime$ and $Z^\prime$ bosons. Upper limits on the cross section are set for resonances with mass between 1.5 and 5.0 TeV, ranging from 6.8 to 0.53 fb for $W^\prime \to WH$ and from 8.7 to 0.53 fb for $Z^\prime \to ZH$ at the 95 % confidence level.
Observed and expected 95% CL upper limits on the cross section in the WH channel.
Observed and expected 95% CL upper limits on the cross section in the ZH channel.
Signal acceptance times efficiency of HVT WH(qqbb) events as a function of the resonance mass at different cut stages. Auxiliary table attached for 2 TeV mass point.
Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton$-$proton collision data corresponding to an integrated luminosity of 139 fb$^{-1}$. The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is $b$-tagged, are selected. The fiducial cross-section is measured to be $39.6\,^{+2.7}_{-2.3}\,\textrm{fb}$. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and angular separations between the two leptons in the event. All measurements are in agreement with the predictions from the Standard Model.
The measured fiducial cross-section in the electron-muon channel. The first uncertainty is the statistical uncertainty and the second one is the systematic uncertainty.
The absolute differential cross-section measured in the fiducial phase-space as a function of the photon pT in the electron-muon channel. The uncertainty is decomposed into four components which are the signal modelling uncertainty, the background modelling uncertainty, the experimental uncertainty, and the data statistical uncertainty.
The absolute differential cross-section measured in the fiducial phase-space as a function of the photon $|\eta|$ in the electron-muon channel. The uncertainty is decomposed into four components which are the signal modelling uncertainty, the background modelling uncertainty, the experimental uncertainty, and the data statistical uncertainty.
The ratios of the production cross sections between the excited $\Upsilon$(2S) and $\Upsilon$(3S) mesons and the $\Upsilon$(1S) ground state, detected via their decay into two muons, are studied as a function of the number of charged particles in the event. The data are from proton-proton collisions at $\sqrt{s} =$ 7 TeV, corresponding to an integrated luminosity of 4.8 fb$^{-1}$, collected with the CMS detector at the LHC. Evidence of a decrease in these ratios as a function of the particle multiplicity is observed, more pronounced at low transverse momentum $p_\mathrm{T}^{\mu\mu}$. For $\Upsilon$(nS) mesons with $p_\mathrm{T}^{\mu\mu}$ $\gt$ 7 GeV, where most of the data were collected, the correlation with multiplicity is studied as a function of the underlying event transverse sphericity and the number of particles in a cone around the $\Upsilon$(nS) direction. The ratios are found to be multiplicity independent for jet-like events. The mean $p_\mathrm{T}^{\mu\mu}$ values for the $\Upsilon$(nS) states as a function of particle multiplicity are also measured and found to grow more steeply as their mass increases.
The measured ratios $\Upsilon(2$S$)\,/\,\Upsilon(1$S$)$ and $\Upsilon(3$S$)\,/\,\Upsilon(1$S$)$ with $p_T(\Upsilon(n$S$))>7\,GeV$ and $|y(\Upsilon(n$S$))| < 1.2$, as a function of track multiplicity $N_{track}$
The measured ratios $\Upsilon(2$S$)\,/\,\Upsilon(1$S$)$ and $\Upsilon(3$S$)\,/\,\Upsilon(1$S$)$ with $p_T(\Upsilon(n$S$))>0\,GeV$ and $|y(\Upsilon(n$S$))| < 1.93$, as a function of track multiplicity $N_{track}$.
Mean $p_T$ values of the $\Upsilon(1$S$)$, $\Upsilon(2$S$)$, and $\Upsilon(3S)$ states with $p_T\,>\,7\,GeV$ and $|y|\,<\,1.2$ as a function of track multiplicity $N_{track}$
Measurements of the Standard Model Higgs boson decaying into a $b\bar{b}$ pair and produced in association with a $W$ or $Z$ boson decaying into leptons, using proton-proton collision data collected between 2015 and 2018 by the ATLAS detector, are presented. The measurements use collisions produced by the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s} = $13 TeV, corresponding to an integrated luminosity of 139 fb$^{-1}$. The production of a Higgs boson in association with a $W$ or $Z$ boson is established with observed (expected) significances of 4.0 (4.1) and 5.3 (5.1) standard deviations, respectively. Cross-sections of associated production of a Higgs boson decaying into bottom quark pairs with an electroweak gauge boson, $W$ or $Z$, decaying into leptons are measured as a function of the gauge boson transverse momentum in kinematic fiducial volumes. The cross-section measurements are all consistent with the Standard Model expectations, and the total uncertainties vary from 30% in the high gauge boson transverse momentum regions to 85% in the low regions. Limits are subsequently set on the parameters of an effective Lagrangian sensitive to modifications of the $WH$ and $ZH$ processes as well as the Higgs boson decay into $b\bar{b}$.
Best-fit values and uncertainties for $VH, V\rightarrow\mathrm{leptons}$ for the cross-section times the $H\rightarrow b\bar{b}$ branching fraction, in the reduced stage-1.2 simplififed template cross-sections (STXS) scheme. The SM predictions for each region is also shown. They are obtained from the samples of simulated events scaled to the inclusive cross-sections calculated at NNLO(QCD)+NLO(EW) accuracy for the $qq\rightarrow WH$ and $qq\rightarrow ZH$ processes, and at NLO+NLL accuracy for the $gg\rightarrow ZH$ process. The contributions to the total uncertainty in the measurements from statistical (Stat.) or systematic uncertainties in the signal modelling (Th. sig.), background modelling (Th. bkg.) and in experimental performance (Exp.) are given separately. All leptonic decays of the $V$ bosons (including those to $\tau$ leptons, $\ell = e, \mu, \tau$) are considered.
Observed correlations between the measured reduced stage-1.2 simplified template $VH, H \rightarrow b\bar{b}$ cross-sections (STXS), including both the statistical and systematic uncertainties. All leptonic decays of the $V$ bosons (including those to $\tau$ leptons, $\ell = e, \mu, \tau$) are considered.
Linear combination of Wilson coefficients corresponding to SMEFT operators in the Warsaw basis for which this analysis provides orthogonal constraints (eigenvectors). Eigenvalues are shown for each eigenvector, which provides a measure of the experimental sensitivity to that linear combination. The modifications to the $qq\rightarrow ZH$ and $qq\rightarrow WH$ processes due to SMEFT operators are computed at LO, and changes to the $gg\rightarrow ZH$ process are neglected.