A search for physics beyond the standard model (SM) in the final state with a hadronically decaying tau lepton and a neutrino is presented. This analysis is based on data recorded by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to a total integrated luminosity of 138 fb$^{=1}$. The transverse mass spectrum is analyzed for the presence of new physics. No significant deviation from the SM prediction is observed. Limits are set on the production cross section of a W' boson decaying into a tau lepton and a neutrino. Lower limits are set on the mass of the sequential SM-like heavy charged vector boson and the mass of a quantum black hole. Upper limits are placed on the couplings of a new boson to the SM fermions. Constraints are put on a nonuniversal gauge interaction model and an effective field theory model. For the first time, upper limits on the cross section of $t$-channel leptoquark (LQ) exchange are presented. These limits are translated into exclusion limits on the LQ mass and on its coupling in the $t$-channel. The sensitivity of this analysis extends into the parameter space of LQ models that attempt to explain the anomalies observed in B meson decays. The limits presented for the various interpretations are the most stringent to date. Additionally, a model-independent limit is provided.
The transverse mass distribution of $ au$ leptons and missing transverse momentum observed in the Run-2 data (black dots with statistical uncertainty) as well as the expectation from SM processes (stacked histograms). Different signal hypotheses normalized to 10 fb$^{-1}$ are illustrated as dashed lines for exemplary SSM W$\prime$ boson, QBH and EFT signal hypotheses. The ratios of the background-subtracted data yields to the expected background yields are presented in the lower panel. The combined statistical and systematic uncertainties in the background are represented by the grey shaded band in the ratio panel.
Bayesian upper exclusion limits at 95% CL on the product of the cross section and branching fraction of a W$\prime$ boson decaying to a $\tau$ lepton and a neutrino in the SSM model. For this model, W$\prime$ boson masses of up to 4.8 TeV can be excluded. The limit is given by the intersection of the observed (solid) limit and the theoretical cross section (blue dotted curve). The 68 and 95% quantiles of the limits are represented by the green and yellow bands, respectively. The $\sigma \mathcal{B}$ for an SSM W' boson, along with its associated uncertainty, calculated at NNLO precision in QCD is shown.
Bayesian 95% CL model-independent upper limit on the product of signal cross sections and branching fraction for the $\tau+\nu$ decay for a back-to-back $\tau$ lepton plus $p_{T}^{miss}$ topology. To calculate this limit, all events for signal, background, and data are summed starting from a minimum $m_{T}$ threshold and then divided by the total number of events. No assumption on signal shape is included in this limit. The expected (dashed line) and observed (solid line) limits are shown as well as the 68% and 95% CL uncertainty bands (green and yellow, respectively).
A search for Higgs boson pair production in events with two $b$-jets and two $\tau$-leptons is presented, using a proton-proton collision dataset with an integrated luminosity of 139 fb$^{-1}$ collected at $\sqrt{s}=13$ TeV by the ATLAS experiment at the LHC. Higgs boson pairs produced non-resonantly or in the decay of a narrow scalar resonance in the mass range from 251 to 1600 GeV are targeted. Events in which at least one $\tau$-lepton decays hadronically are considered, and multivariate discriminants are used to reject the backgrounds. No significant excess of events above the expected background is observed in the non-resonant search. The largest excess in the resonant search is observed at a resonance mass of 1 TeV, with a local (global) significance of $3.1\sigma$ ($2.0\sigma$). Observed (expected) 95% confidence-level upper limits are set on the non-resonant Higgs boson pair-production cross-section at 4.7 (3.9) times the Standard Model prediction, assuming Standard Model kinematics, and on the resonant Higgs boson pair-production cross-section at between 21 and 900 fb (12 and 840 fb), depending on the mass of the narrow scalar resonance.
Breakdown of the relative contributions to the uncertainty in the extracted signal cross-sections, as determined in the likelihood fit (described in Section 8) to data. These are obtained by fixing the relevant nuisance parameters in the likelihood fit, and subtracting the obtained uncertainty on the fitted signal cross-sections in quadrature from the total uncertainty, and then dividing the result by the total uncertainty. The sum in quadrature of the individual components differs from the total uncertainty due to correlations between uncertainties in the different groups.
Post-fit expected number of signal and background events and observed number of data events in the last two bins of the non-resonant BDT score distribution of the SM signal after applying the selection criteria and requiring exactly 2 b-tagged jets and assuming a background-only hypothesis
Observed and expected upper limits at 95% CL on the cross-section of non-resonant HH production according to SM-like kinematics, and on the cross-section of non-resonant HH production divided by the SM prediction. The 1 sigma and 2 sigma variations around the expected limit are also shown.
A search for new phenomena has been performed in final states with at least one isolated high-momentum photon, jets and missing transverse momentum in proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. The data, collected by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 $fb^{-1}$. The experimental results are interpreted in a supersymmetric model in which pair-produced gluinos decay into neutralinos, which in turn decay into a gravitino, at least one photon, and jets. No significant deviations from the predictions of the Standard Model are observed. Upper limits are set on the visible cross section due to physics beyond the Standard Model, and lower limits are set on the masses of the gluinos and neutralinos, all at 95% confidence level. Visible cross sections greater than 0.022 fb are excluded and pair-produced gluinos with masses up to 2200 GeV are excluded for most of the NLSP masses investigated.
The observed and expected (post-fit) yields in the control and validation regions. The lower panel shows the difference in standard deviations between the observed and expected yields, considering both the systematic and statistical uncertainties on the background expectation.
Observed (points with error bars) and expected background (solid histograms) distributions for $E_{T}^{miss}$ in the signal region (a) SRL, (b) SRM and (c) SRH after the background-only fit applied to the CRs. The predicted signal distributions for the two models with a gluino mass of 2000 GeV and neutralino mass of 250 GeV (SRL), 1050 GeV (SRM) or 1950 GeV (SRH) are also shown for comparison. The uncertainties in the SM background are only statistical.
Observed (points with error bars) and expected background (solid histograms) distributions for $E_{T}^{miss}$ in the signal region (a) SRL, (b) SRM and (c) SRH after the background-only fit applied to the CRs. The predicted signal distributions for the two models with a gluino mass of 2000 GeV and neutralino mass of 250 GeV (SRL), 1050 GeV (SRM) or 1950 GeV (SRH) are also shown for comparison. The uncertainties in the SM background are only statistical.
This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb$^{-1}$ of proton-proton collisions at $\sqrt{s}=13$ TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, ${\mathrm{d}}E/\mathrm{d}x$. Trajectories reconstructed solely by the inner tracking system and a ${\mathrm{d}}E/\mathrm{d}x$ measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to ${\cal O}(1)$$\text{ns}$ with a mass, measured using the Bethe--Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of $R$-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime.
This material aims to give people outside the ATLAS Collaboration the possibility to reinterpret the results from the search for heavy charged long-lived particles (CLLPs), using only particles from Monte Carlo event generators. The reinterpretation material is provided for signal regions SR-Inclusive_Low and SR-Inclusive_High. <ul display="inline-block"> <li>The "long" lifetime regime of mass windows is used.</li> <li>Users are guided to read Guide.pdf (available from "Resources" or "Download All" buttons) for how to use the provided materials for reinterpretation.</li> <li>The pseudo-code snippet snippet.cxx also illustrates a sketch of possible implementation.</li> </ul> <b>Signal Region (Discovery) mass distribution</b> <ul> <li><a href="?table=SR-Inclusive_Low%20mass%20distribution">SR-Inclusive_Low mass distribution</a></li> <li><a href="?table=SR-Inclusive_High%20mass%20distribution">SR-Inclusive_High mass distribution</a></li> </ul> <b>Signal Region (Discovery) $p_\text{T}, \eta, dE/dx$ distribution</b> <ul> <li><a href="?table=SR-Inclusive_Low%20pT%20distribution">SR-Inclusive_Low pT distribution</a></li> <li><a href="?table=SR-Inclusive_High%20pT%20distribution">SR-Inclusive_High pT distribution</a></li> <li><a href="?table=SR-Inclusive_Low%20$eta$%20distribution">SR-Inclusive_Low $\eta$ distribution</a></li> <li><a href="?table=SR-Inclusive_High%20$eta$%20distribution">SR-Inclusive_High $\eta$ distribution</a></li> <li><a href="?table=SR-Inclusive_Low%20dE/dx%20distribution">SR-Inclusive_Low dE/dx distribution</a></li> <li><a href="?table=SR-Inclusive_High%20dE/dx%20distribution">SR-Inclusive_High dE/dx distribution</a></li> </ul> <b>Signal Region (Limit Setting) mass distribution</b> <ul> <li><a href="?table=SR-Trk-IBL0_Low%20mass%20distribution">SR-Trk-IBL0_Low mass distribution</a></li> <li><a href="?table=SR-Mu-IBL0_Low%20mass%20distribution">SR-Mu-IBL0_Low mass distribution</a></li> <li><a href="?table=SR-Trk-IBL0_High%20mass%20distribution">SR-Trk-IBL0_High mass distribution</a></li> <li><a href="?table=SR-Mu-IBL0_High%20mass%20distribution">SR-Mu-IBL0_High mass distribution</a></li> <li><a href="?table=SR-Trk-IBL1%20mass%20distribution">SR-Trk-IBL1 mass distribution</a></li> <li><a href="?table=SR-Mu-IBL1%20mass%20distribution">SR-Mu-IBL1 mass distribution</a></li> </ul> <b>Signal Region (Limit Setting) $p_\text{T}$ distribution</b> <ul> <li><a href="?table=SR-Trk-IBL0_Low%20pT%20distribution">SR-Trk-IBL0_Low pT distribution</a></li> <li><a href="?table=SR-Mu-IBL0_Low%20pT%20distribution">SR-Mu-IBL0_Low pT distribution</a></li> <li><a href="?table=SR-Trk-IBL0_High%20pT%20distribution">SR-Trk-IBL0_High pT distribution</a></li> <li><a href="?table=SR-Mu-IBL0_High%20pT%20distribution">SR-Mu-IBL0_High pT distribution</a></li> <li><a href="?table=SR-Trk-IBL1%20pT%20distribution">SR-Trk-IBL1 pT distribution</a></li> <li><a href="?table=SR-Mu-IBL1%20pT%20distribution">SR-Mu-IBL1 pT distribution</a></li> </ul> <b>Signal Region (Limit Setting) $dE/dx$ distribution</b> <ul> <li><a href="?table=SR-Trk-IBL0_Low%20dE/dx%20distribution">SR-Trk-IBL0_Low dE/dx distribution</a></li> <li><a href="?table=SR-Mu-IBL0_Low%20dE/dx%20distribution">SR-Mu-IBL0_Low dE/dx distribution</a></li> <li><a href="?table=SR-Trk-IBL0_High%20dE/dx%20distribution">SR-Trk-IBL0_High dE/dx distribution</a></li> <li><a href="?table=SR-Mu-IBL0_High%20dE/dx%20distribution">SR-Mu-IBL0_High dE/dx distribution</a></li> <li><a href="?table=SR-Trk-IBL1%20dE/dx%20distribution">SR-Trk-IBL1 dE/dx distribution</a></li> <li><a href="?table=SR-Mu-IBL1%20dE/dx%20distribution">SR-Mu-IBL1 dE/dx distribution</a></li> </ul> <b>Discovery Signal Regions $p_{0}$ values</b> <ul> <li><a href="?table=p0-values%20and%20model-independent%20limits,%20short%20regime">p0-values and model-independent limits, short regime</a></li> <li><a href="?table=p0-values%20and%20model-independent%20limits,%20long%20regime">p0-values and model-independent limits, long regime</a></li> </ul> <b>Validation Region plots</b> <ul> <li><a href="?table=VR-LowPt-Inclusive_High%20mass%20distribution">VR-LowPt-Inclusive_High mass distribution</a></li> <li><a href="?table=VR-HiEta-Inclusive%20mass%20distribution">VR-HiEta-Inclusive mass distribution</a></li> </ul> <ul> <li><a href="?table=VR-LowPt-Trk-IBL0_Low%20mass%20distribution">VR-LowPt-Trk-IBL0_Low mass distribution</a></li> <li><a href="?table=VR-LowPt-Mu-IBL0_Low%20mass%20distribution">VR-LowPt-Mu-IBL0_Low mass distribution</a></li> <li><a href="?table=VR-LowPt-Trk-IBL0_High%20mass%20distribution">VR-LowPt-Trk-IBL0_High mass distribution</a></li> <li><a href="?table=VR-LowPt-Mu-IBL0_High%20mass%20distribution">VR-LowPt-Mu-IBL0_High mass distribution</a></li> <li><a href="?table=VR-LowPt-Trk-IBL1%20mass%20distribution">VR-LowPt-Trk-IBL1 mass distribution</a></li> <li><a href="?table=VR-LowPt-Mu-IBL1%20mass%20distribution">VR-LowPt-Mu-IBL1 mass distribution</a></li> </ul> <ul> <li><a href="?table=VR-HiEta-Trk-IBL0_Low%20mass%20distribution">VR-HiEta-Trk-IBL0_Low mass distribution</a></li> <li><a href="?table=VR-HiEta-Mu-IBL0_Low%20mass%20distribution">VR-HiEta-Mu-IBL0_Low mass distribution</a></li> <li><a href="?table=VR-HiEta-Trk-IBL0_High%20mass%20distribution">VR-HiEta-Trk-IBL0_High mass distribution</a></li> <li><a href="?table=VR-HiEta-Mu-IBL0_High%20mass%20distribution">VR-HiEta-Mu-IBL0_High mass distribution</a></li> <li><a href="?table=VR-HiEta-Trk-IBL1%20mass%20distribution">VR-HiEta-Trk-IBL1 mass distribution</a></li> <li><a href="?table=VR-HiEta-Mu-IBL1%20mass%20distribution">VR-HiEta-Mu-IBL1 mass distribution</a></li> </ul> <b>Mass vs. Lifetime limit plots</b> <ul> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20R-hadron,%20Expected">Mass Limit vs. Lifetime, R-hadron, Expected</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20R-hadron,%20Observed">Mass Limit vs. Lifetime, R-hadron, Observed</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20R-hadron,%20compressed,%20Expected">Mass Limit vs. Lifetime, R-hadron, compressed, Expected</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20R-hadron,%20compressed,%20Observed">Mass Limit vs. Lifetime, R-hadron, compressed, Observed</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20Chargino,%20Expected">Mass Limit vs. Lifetime, Chargino, Expected</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20Chargino,%20Observed">Mass Limit vs. Lifetime, Chargino, Observed</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20Stau,%20Expected">Mass Limit vs. Lifetime, Stau, Expected</a></li> <li><a href="?table=Mass%20Limit%20vs.%20Lifetime,%20Stau,%20Observed">Mass Limit vs. Lifetime, Stau, Observed</a></li> </ul> <b>Cross-section limit plots</b> <ul> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%201ns">Cross Section Limit, R-hadron 1ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%203ns">Cross Section Limit, R-hadron 3ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%2010ns">Cross Section Limit, R-hadron 10ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%2030ns">Cross Section Limit, R-hadron 30ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%20Stable">Cross Section Limit, R-hadron Stable</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%20Compressed%201ns">Cross Section Limit, R-hadron Compressed 1ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%20Compressed%203ns">Cross Section Limit, R-hadron Compressed 3ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%20Compressed%2010ns">Cross Section Limit, R-hadron Compressed 10ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20R-hadron%20Compressed%2030ns">Cross Section Limit, R-hadron Compressed 30ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Chargino%201ns">Cross Section Limit, Chargino 1ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Chargino%204ns">Cross Section Limit, Chargino 4ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Chargino%2010ns">Cross Section Limit, Chargino 10ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Chargino%2030ns">Cross Section Limit, Chargino 30ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Chargino%20Stable">Cross Section Limit, Chargino Stable</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Stau%201ns">Cross Section Limit, Stau 1ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Stau%203ns">Cross Section Limit, Stau 3ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Stau%2010ns">Cross Section Limit, Stau 10ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Stau%2030ns">Cross Section Limit, Stau 30ns</a></li> <li><a href="?table=Cross%20Section%20Limit,%20Stau%20Stable">Cross Section Limit, Stau Stable</a></li> </ul> <b>Signal Region events projected to other kinematic variables</b> <ul> <li><a href="?table=SR-Inclusive_Low%20MET">SR-Inclusive_Low MET</a></li> <li><a href="?table=SR-Inclusive_High%20MET">SR-Inclusive_High MET</a></li> <li><a href="?table=SR-Inclusive_Low%20deltaPhi(MET,%20Track)">SR-Inclusive_Low deltaPhi(MET, Track)</a></li> <li><a href="?table=SR-Inclusive_High%20deltaPhi(MET,%20Track)">SR-Inclusive_High deltaPhi(MET, Track)</a></li> <li><a href="?table=SR-Inclusive_Low%20mT(MET,%20Track)">SR-Inclusive_Low mT(MET, Track)</a></li> <li><a href="?table=SR-Inclusive_High%20mT(MET,%20Track)">SR-Inclusive_High mT(MET, Track)</a></li> <li><a href="?table=SR-Inclusive_Low%20Leading%20jet%20pT">SR-Inclusive_Low Leading jet pT</a></li> <li><a href="?table=SR-Inclusive_High%20Leading%20jet%20pT">SR-Inclusive_High Leading jet pT</a></li> <li><a href="?table=SR-Inclusive_Low%20deltaPhi(Leading%20jet,%20Track)">SR-Inclusive_Low deltaPhi(Leading jet, Track)</a></li> <li><a href="?table=SR-Inclusive_High%20deltaPhi(Leading%20jet,%20Track)">SR-Inclusive_High deltaPhi(Leading jet, Track)</a></li> <li><a href="?table=SR-Inclusive_Low%20deltaPhi(MET,%20Leading%20jet)">SR-Inclusive_Low deltaPhi(MET, Leading jet)</a></li> <li><a href="?table=SR-Inclusive_High%20deltaPhi(MET,%20Leading%20jet)">SR-Inclusive_High deltaPhi(MET, Leading jet)</a></li> <li><a href="?table=SR-Inclusive_Low%20mT(MET,%20Leading%20jet)">SR-Inclusive_Low mT(MET, Leading jet)</a></li> <li><a href="?table=SR-Inclusive_High%20mT(MET,%20Leading%20jet)">SR-Inclusive_High mT(MET, Leading jet)</a></li> <li><a href="?table=SR-Inclusive_Low%20Effective%20mass">SR-Inclusive_Low Effective mass</a></li> <li><a href="?table=SR-Inclusive_High%20Effective%20mass">SR-Inclusive_High Effective mass</a></li> </ul> <b>Acceptance and efficiency values for reinterpretation</b> <ul> <li><a href="?table=Muon%20Reconstruction%20Efficiency%20distribution">Muon Reconstruction Efficiency distribution</a></li> <li><a href="?table=Muon%20Reconstruction%20Efficiency,%20R-hadron%20distribution">Muon Reconstruction Efficiency, R-hadron distribution</a></li> <li><a href="?table=Trigger%20Efficiency%20distribution">Trigger Efficiency distribution</a></li> <li><a href="?table=Event%20Selection%20Efficiency%20distribution">Event Selection Efficiency distribution</a></li> <li><a href="?table=Track%20Selection%20Efficiency%20distribution">Track Selection Efficiency distribution</a></li> <li><a href="?table=Mass%20Window%20Efficiency">Mass Window Efficiency</a></li> </ul> <b>Acceptance and efficiency tables for signal samples</b> <ul> <li><a href="?table=Acceptance,%20R-hadron">Acceptance, R-hadron</a></li> <li><a href="?table=Acceptance,%20R-hadron,%20compressed">Acceptance, R-hadron, compressed</a></li> <li><a href="?table=Acceptance,%20Chargino">Acceptance, Chargino</a></li> <li><a href="?table=Acceptance,%20Stau">Acceptance, Stau</a></li> </ul> <ul> <li><a href="?table=Event-level%20efficiency,%20R-hadron">Event-level efficiency, R-hadron</a></li> <li><a href="?table=Event-level%20efficiency,%20R-hadron,%20compressed">Event-level efficiency, R-hadron, compressed</a></li> <li><a href="?table=Event-level%20efficiency,%20Chargino">Event-level efficiency, Chargino</a></li> <li><a href="?table=Event-level%20efficiency,%20Stau">Event-level efficiency, Stau</a></li> </ul> <ul> <li><a href="?table=Efficiency,%20SR-Inclusve_High,%20R-hadron">Efficiency, SR-Inclusve_High, R-hadron</a></li> <li><a href="?table=Efficiency,%20SR-Inclusve_High,%20R-hadron,%20compressed">Efficiency, SR-Inclusve_High, R-hadron, compressed</a></li> <li><a href="?table=Efficiency,%20SR-Inclusve_High,%20Chargino">Efficiency, SR-Inclusve_High, Chargino</a></li> <li><a href="?table=Efficiency,%20SR-Inclusve_High,%20Stau">Efficiency, SR-Inclusve_High, Stau</a></li> </ul> <ul> <li><a href="?table=Efficiency,%20SR-Inclusive_Low,%20R-hadron">Efficiency, SR-Inclusive_Low, R-hadron</a></li> <li><a href="?table=Efficiency,%20SR-Inclusive_Low,%20R-hadron,%20compressed">Efficiency, SR-Inclusive_Low, R-hadron, compressed</a></li> <li><a href="?table=Efficiency,%20SR-Inclusive_Low,%20Chargino">Efficiency, SR-Inclusive_Low, Chargino</a></li> <li><a href="?table=Efficiency,%20SR-Inclusive_Low,%20Stau">Efficiency, SR-Inclusive_Low, Stau</a></li> </ul> <b>Cut flow for signal samples</b> <ul> <li><a href="?table=Cut%20Flow,%20R-hadron">Cut Flow, R-hadron</a></li> <li><a href="?table=Cut%20Flow,%20R-hadron,%20compressed">Cut Flow, R-hadron, compressed</a></li> <li><a href="?table=Cut%20Flow,%20Chargino">Cut Flow, Chargino</a></li> <li><a href="?table=Cut%20Flow,%20Stau">Cut Flow, Stau</a></li> </ul>
Comparison of the observed and expected VAR distributionsin VR-LowPt-Inclusive_High. The band on the expected background estimation indicates the total uncertainty of the estimation. Downward triangle markers at the bottom of the panels indicate there is no events observed in the corresponding bin, while upward triangle markers at the bottom panel indicate the observed data is beyond the range.
Comparison of the observed and expected VAR distributionsin VR-HiEta-Inclusive. The band on the expected background estimation indicates the total uncertainty of the estimation. Downward triangle markers at the bottom of the panels indicate there is no events observed in the corresponding bin, while upward triangle markers at the bottom panel indicate the observed data is beyond the range.
A search for a heavy resonance decaying into a top quark and a W boson in proton-proton collisions at $\sqrt{s} =$ 13 TeV is presented. The data analyzed were recorded with the CMS detector at the LHC and correspond to an integrated luminosity of 138 fb$^{-1}$. The top quark is reconstructed as a single jet and the W boson, from its decay into an electron or muon and the corresponding neutrino. A top quark tagging technique based on jet clustering with a variable distance parameter and simultaneous jet grooming is used to identify jets from the collimated top quark decay. The results are interpreted in the context of two benchmark models, where the heavy resonance is either an excited bottom quark b$^*$ or a vector-like quark B. A statistical combination with an earlier search by the CMS Collaboration in the all-hadronic final state is performed to place upper cross section limits on these two models. The new analysis extends the lower range of resonance mass probed from 1.4 down to 0.7 TeV. For left-handed, right-handed, and vector-like couplings, b$^*$ masses up to 3.0, 3.0, and 3.2 TeV are excluded at 95% confidence level, respectively. The observed upper limits represent the most stringent constraints on the b$^*$ model to date.
Distributions of MtW in the 1b category. The data are shown by filled markers, where the horizontal bars indicate the bin widths. The individual background contributions are given by filled histograms. The expected signal for a LH b* with mb∗ = 2.4 TeV is shown by a dashed line. The shaded region is the uncertainty in the total background estimate. The lower panel shows the ratio of data to the background estimate, with the total uncertainty on the predicted background displayed as the gray band.
Distributions of MtW in the 2b category. The data are shown by filled markers, where the horizontal bars indicate the bin widths. The individual background contributions are given by filled histograms. The expected signal for a LH b* with mb∗ = 2.4 TeV is shown by a dashed line. The shaded region is the uncertainty in the total background estimate. The lower panel shows the ratio of data to the background estimate, with the total uncertainty on the predicted background displayed as the gray band.
Upper limits on the production cross section times branching fraction of the b* LH hypothesis at a 95% CL. Dashed colored lines show the expected limits from the l+jets and all-hadronic channels, where the latter start at resonance masses of 1.4 TeV. The observed and expected limits from the combination are shown as solid and dashed black lines, respectively. The green and yellow bands show the 68 and 95% confidence intervals on the combined expected limits.
Dijet angular distributions from the first LHC pp collisions at center-of-mass energy sqrt(s) = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb-1. Dijet $\chi$ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the $\chi$ distributions excludes quark contact interactions with a compositeness scale $\Lambda$ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.
CHI distribution for mass bin 340 to 520 GeV.
CHI distribution for mass bin 520 to 800 GeV.
CHI distribution for mass bin 800 to 1200 GeV.
A search for new heavy particles manifested as resonances in two-jet final states is presented. The data were produced in 7 TeV proton-proton collisions by the Large Hadron Collider (LHC) and correspond to an integrated luminosity of 315 nb^-1 collected by the ATLAS detector. No resonances were observed. Upper limits were set on the product of cross section and signal acceptance for excited-quark (q*) production as a function of q* mass. These exclude at the 95% CL the q* mass interval 0.30 < mq* < 1.26 TeV, extending the reach of previous experiments.
The dijet mass distribution (NUMBER OF EVENTS).
95 PCT CL upper limit of the cross section x acceptance.
We present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e+e- pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au+Au data at sqrt(s_NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au^{star} nuclei. The event sample consists of 28 events with m_{e+e-} > 2 GeV/c^2 with zero like-sign background. The measured cross sections at midrapidity of d\sigma / dy (J/psi + Xn, y=0) = 76 +/- 33 (stat) +/- 11 (syst) micro b and d^2\sigma/dm dy (e^+e^- + Xn, y=0) = 86 +/- 23 (stat) +/- 16 (syst) micro b/(GeV/c^2) for m_{e+e-} \in [2.0,2.8] GeV/c^2 are consistent with various theoretical predictions.
J/PSI N for ultra peripheral Au+Au reactions. The values has been obtained from the fit of the number of counts as a function of the mass of the e+e- pairs detected. The J/PSI pick has been fixed at the known mass ofJ/PSI : 3.097 GeV/c2.
e+e- pairs N in ultra peripherals Au + Au reactions. The values has been obtained from the fit of the number of counts as a function of the mass of the e+e- pairs.The results are given for 3 intervals of masses of the electron pair : 2.0 to 2.3, 2.3 to 2.8 and 2.0 to 2.8 Gev/c2.
J/PSI production cross section at mid rapidity for ultra peripheral Au+Au reactions.
The production of two high-p_T jets in the interactions of quasi-real photons in e+e- collisions at sqrt{s_ee} from 189 GeV to 209 GeV is studied with data corresponding to an integrated e+e- luminosity of 550 pb^{-1}. The jets reconstructed by the k_T cluster algorithm are defined within the pseudo-rapidity range -1 < eta < 1 and with jet transverse momentum, p_T, above 3 GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum ptmean of the jets and is compared to perturbative QCD calculations.
Total cross section for dijet production. Errors are combined statistics and systematics.
Measured dijet production cross section as a function of the mean jet transverse momentum. Errors include both statistics and systematics.
Measured dijet production cross section as a function of jet pseudorapiditydifference. Errors include both statistics and systematics.
We present measurements of the total production rates and momentum distributions of the charmed baryon $\Lambda_c^+$ in $e^+e^- \to$ hadrons at a center-of-mass energy of 10.54 GeV and in $\Upsilon(4S)$ decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in $e^+e^- \to c\bar{c}$ events, allowing direct studies of $c$-quark fragmentation. We measure a momentum distribution for $\Lambda_c^+$ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of $\left< x_p \right> = 0.574\pm$0.009 and a total rate of $N_{\Lambda c}^{q\bar{q}} = 0.057\pm$0.002(exp.)$\pm$0.015(BF) $\Lambda_c^+$ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, $pK^-\pi^+$. In $\Upsilon (4S)$ decays we measure a total rate of $N_{\Lambda c}^{\Upsilon} = 0.091\pm$0.006(exp.)$\pm$0.024(BF) per $\Upsilon(4S)$ decay, and find a much softer momentum distribution than expected from B decays into a $\Lambda_c^+$ plus an antinucleon and one to three pions.
LAMBDA/C+ differential production rate per hadronic event for the continuum at cm energy 10.54 GeV.
The integrated number of LAMBDA/C+'s per hadronic event for the continuum at cm energy 10.54 GeV.
LAMBDA/C+ differential production rate per UPSILON(4S) decay at cm energy 10.58 GeV.