A search is presented for vector-like T and B quark-antiquark pairs produced in proton-proton collisions at a center-of-mass energy of 13 TeV. Data were collected by the CMS experiment at the CERN LHC in 2016-2018, with an integrated luminosity of 138 fb$^{-1}$. Events are separated into single-lepton, same-sign charge dilepton, and multilepton channels. In the analysis of the single-lepton channel a multilayer neural network and jet identification techniques are employed to select signal events, while the same-sign dilepton and multilepton channels rely on the high-energy signature of the signal to distinguish it from standard model backgrounds. The data are consistent with standard model background predictions, and the production of vector-like quark pairs is excluded at 95% confidence level for T quark masses up to 1.54 TeV and B quark masses up to 1.56 TeV, depending on the branching fractions assumed, with maximal sensitivity to decay modes that include multiple top quarks. The limits obtained in this search are the strongest limits to date for $\mathrm{T\overline{T}}$ production, excluding masses below 1.48 TeV for all decays to third generation quarks, and are the strongest limits to date for $\mathrm{B\overline{B}}$ production with B quark decays to tW.
Distribution of ST in the training region for the $T\overline{T}$ MLP. The observed data are shown along with the predicted $T\overline{T}$ signal with mass of 1.2 (1.5) TeV in the singlet scenario and the background. Statistical and systematic uncertainties in the background prediction before performing the fit to data are also shown. The signal predictions of 1.2 TeV and 1.5 TeV signals have been scaled by factors of x300 and x600, respectively, for visibility.
Distribution of the leading jet’s DEEPAK8 light quark or gluon score in the training region for the $T\overline{T}$ MLP. The observed data are shown along with the predicted $T\overline{T}$ signal with mass of 1.2 (1.5) TeV in the singlet scenario and the background. Statistical and systematic uncertainties in the background prediction before performing the fit to data are also shown. The signal predictions of 1.2 TeV and 1.5 TeV signals have been scaled by factors of x300 and x600, respectively, for visibility.
Distribution of the MLP T quark score in the SR for the $T\overline{T}$ search. The observed data, predicted $T\overline{T}$ signal with mass of 1.2 (1.5) TeV in the singlet scenario, and the background are all shown. Statistical and systematic uncertainties in the background prediction before performing the fit to data are also shown. The signal predictions of 1.2 TeV and 1.5 TeV signals have been scaled by factors of x10 and x20, respectively, for visibility.
A search for long-lived particles decaying into muon pairs is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2017 and 2018, corresponding to an integrated luminosity of 101 fb$^{-1}$. The data sets used in this search were collected with a dedicated dimuon trigger stream with low transverse momentum thresholds, recorded at high rate by retaining a reduced amount of information, in order to explore otherwise inaccessible phase space at low dimuon mass and nonzero displacement from the primary interaction vertex. No significant excess of events beyond the standard model expectation is found. Upper limits on branching fractions at 95% confidence level are set on a wide range of mass and lifetime hypotheses in beyond the standard model frameworks with the Higgs boson decaying into a pair of long-lived dark photons, or with a long-lived scalar resonance arising from a decay of a b hadron. The limits are the most stringent to date for substantial regions of the parameter space. These results can be also used to constrain models of displaced dimuons that are not explicitly considered in this paper.
Expected and observed limits at 95% CL on the branching fraction B(hb --> PHI X) . B(PHI --> mu+mu-) as a function of signal mass for signal lifetime of 1 mm
Expected and observed limits at 95% CL on the branching fraction B(hb --> PHI X) . B(PHI --> mu+mu-) as a function of signal mass for signal lifetime of 100 mm
Expected and observed limits at 95% CL on the branching fraction B(H --> ZD ZD) . B(ZD --> mu+mu-) as a function of signal mass for signal lifetime of 1 mm
Protons consist of three valence quarks, two up-quarks and one down-quark, held together by gluons and a sea of quark-antiquark pairs. Collectively, quarks and gluons are referred to as partons. In a proton-proton collision, typically only one parton of each proton undergoes a hard scattering - referred to as single-parton scattering - leaving the remainder of each proton only slightly disturbed. Here, we report the study of double- and triple-parton scatterings through the simultaneous production of three J/$\psi$ mesons, which consist of a charm quark-antiquark pair, in proton-proton collisions recorded with the CMS experiment at the Large Hadron Collider. We observed this process - reconstructed through the decays of J/$\psi$ mesons into pairs of oppositely charged muons - with a statistical significance above five standard deviations. We measured the inclusive fiducial cross section to be 272 $^{+141}_{-104}$ (stat) $\pm$ 17 (syst) fb, and compared it to theoretical expectations for triple-J/$\psi$ meson production in single-, double- and triple-parton scattering scenarios. Assuming factorization of multiple hard-scattering probabilities in terms of single-parton scattering cross sections, double- and triple-parton scattering are the dominant contributions for the measured process.
Dimuon invariant mass ($m$), proper decay-length ($L$), transverse momentum ($p_{T}$), rapidity ($y$), and azimuthal angle ($\phi$) of each of the three $J/\psi$ candidates measured in the six triple-$J/\psi$ events passing our selection criteria.
Measured DPS effective cross section
$pp \rightarrow J/\psi J/\psi J/\psi X~$ fiducial cross section
A search is described for the production of a pair of bottom-type vector-like quarks (VLQs), each decaying into a b or $\mathrm{\bar{b}}$ quark and either a Higgs or a Z boson, with a mass greater than 1000 GeV. The analysis is based on data from proton-proton collisions at a 13 TeV center-of-mass energy recorded at the CERN LHC, corresponding to a total integrated luminosity of 137 fb$^{-1}$. As the predominant decay modes of the Higgs and Z bosons are to a pair of quarks, the analysis focuses on final states consisting of jets resulting from the six quarks produced in the events. Since the two jets produced in the decay of a highly Lorentz-boosted Higgs or Z boson can merge to form a single jet, nine independent analyses are performed, categorized by the number of observed jets and the reconstructed event mode. No signal in excess of the expected background is observed. Lower limits are set on the VLQ mass at 95% confidence level equal to 1570 GeV in the case where the VLQ decays exclusively to a b quark and a Higgs boson, 1390 GeV for when it decays exclusively to a b quark and a Z boson, and 1450 GeV for when it decays equally in these two modes. These limits represent significant improvements over the previously published VLQ limits.
Measured values of the trigger efficiencies for events with $\HT > 1350\GeV$. The uncertainties are statistical only.
Reconstructed VLQ mass distributions for simulated signal events with a generated VLQ mass $m_{B} = 1200\GeV$. A moderate requirement of $\chi^{2}$/ndf < 2$ is applied to the events. Mass distributions for 4-jet (left), 5-jet (center), and 6-jet (right) events are shown for the three decay modes: bHbH (upper row), bHbZ (middle row), and bZbZ (lower row).
Reconstructed VLQ mass distributions for simulated signal events with a generated VLQ mass $m_{B} = 1200\GeV$. A moderate requirement of $\chi^{2}$/ndf < 2$ is applied to the events. Mass distributions for 4-jet (left), 5-jet (center), and 6-jet (right) events are shown for the three decay modes: bHbH (upper row), bHbZ (middle row), and bZbZ (lower row).
A top quark mass measurement is performed using 35.9 fb$^{-1}$ of LHC proton-proton collision data collected with the CMS detector at $\sqrt{s} =$ 13 TeV. The measurement uses the $\mathrm{t\overline{t}}$ all-jets final state. A kinematic fit is performed to reconstruct the decay of the $\mathrm{t\overline{t}}$ system and suppress the multijet background. Using the ideogram method, the top quark mass ($m_\mathrm{t}$) is determined, simultaneously constraining an additional jet energy scale factor (JSF). The resulting value of $m_\mathrm{t}$ = 172.34 $\pm$ 0.20 (stat+JSF) $\pm$ 0.70 (syst) GeV is in good agreement with previous measurements. In addition, a combined measurement that uses the $\mathrm{t\overline{t}}$ lepton+jets and all-jets final states is presented, using the same mass extraction method, and provides an $m_\mathrm{t}$ measurement of 172.26 $\pm$ 0.07 (stat+JSF) $\pm$ 0.61 (syst) GeV. This is the first combined $m_\mathrm{t}$ extraction from the lepton+jets and all-jets channels through a single likelihood function.
Measured top quark mass $m_{t}$
The mass of the top quark is measured using a sample of $\mathrm{t\overline{t}}$ events collected by the CMS detector using proton-proton collisions at $\sqrt{s} =$ 13 TeV at the CERN LHC. Events are selected with one isolated muon or electron and at least four jets from data corresponding to an integrated luminosity of 35.9 fb$^{-1}$. For each event the mass is reconstructed from a kinematic fit of the decay products to a $\mathrm{t\overline{t}}$ hypothesis. Using the ideogram method, the top quark mass is determined simultaneously with an overall jet energy scale factor (JSF), constrained by the mass of the W boson in $\mathrm{q\overline{q}'}$ decays. The measurement is calibrated on samples simulated at next-to-leading order matched to a leading-order parton shower. The top quark mass is found to be 172.25 $\pm$ 0.08 (stat+JSF) $\pm$ 0.62 (syst) GeV. The dependence of this result on the kinematic properties of the event is studied and compared to predictions of different models of $\mathrm{t\overline{t}}$ production, and no indications of a bias in the measurements are observed.
Measured top quark mass $m_{t}$
A search for a heavy neutral Higgs boson, $A$, decaying into a $Z$ boson and another heavy Higgs boson, $H$, is performed using a data sample corresponding to an integrated luminosity of 36.1 fb$^{-1}$ from proton-proton collisions at $\sqrt{s} = 13$ TeV recorded in 2015 and 2016 by the ATLAS detector at the Large Hadron Collider. The search considers the $Z$ boson decaying to electrons or muons and the $H$ boson into a pair of $b$-quarks. No evidence for the production of an $A$ boson is found. Considering each production process separately, the 95% confidence-level upper limits on the $pp\rightarrow A\rightarrow ZH$ production cross-section times the branching ratio $H\rightarrow bb$ are in the range of 14-830 fb for the gluon-gluon fusion process and 26-570 fb for the $b$-associated process for the mass ranges 130-700 GeV of the $H$ boson and process for the mass ranges 130-700 GeV of the $H$ boson and 230-800 GeV of the $A$ boson. The results are interpreted in the context of the two-Higgs-doublet model.
The signal efficiency for the production modes (gluon-gluon fusion and b-associated production) and the signal regions used in the analysis. The efficiency denominator has the total number of generated MC events. The numerator includes the events passing the full signal region selection, including the mbb window cuts. The table shows for each signal mass pair (mA, mH) 3 efficiencies corresponding to the two production modes in the two categories, 2tag and 3tag. These corresponds to "nb = 2 category" and "nb >= 3 category", respectively, of the preprint. No numbers for gluon-gluon fusion in the 3tag category are provided since those are not used in the analysis. The efficiencies are given in fractions.
The cross section times BR(A->ZH) times BR(H->bb) limits for a narrow width A boson produced via gluon-gluon fusion. For each signal point, characterised by the mass pair (mA, mH), two limits are provided, the observed and the expected. The result refers to the nb=2 category only.
The cross section times BR(A->ZH) times BR(H->bb) limits for a narrow width A boson produced in association with b-quarks. For each signal point, characterised by the mass pair (mA, mH), two limits are provided, the observed and the expected. The result refers to the combination of the nb=2 and nb>=3 categories.
Results of a search for physics beyond the Standard Model in events containing an energetic photon and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. As the number of events observed in data, corresponding to an integrated luminosity of 36.1 $\textrm fb^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV, is in agreement with the Standard Model expectations, exclusion limits in models where dark-matter candidates are pair-produced are determined. For dark-matter production via an axial-vector or a vector mediator in the s-channel, this search excludes mediator masses below 750-1200 GeV for dark-matter candidate masses below 230-480 GeV at 95% confidence level, depending on the couplings. In an effective theory of dark-matter production, the limits restrict the value of the suppression scale $M_{*}$ to be above 790 GeV at 95% confidence level. A limit is also reported on the production of a high-mass scalar resonance by processes beyond the Standard Model, in which the resonance decays to $Z\gamma$ and the Z boson subsequently decays into neutrinos.
Observed event yields in 36.1 fb$^{-1}$ of data compared to expected yields from SM backgrounds in all signal regions, as predicted from the simultaneous fit to their respective CRs. The first three lines report the yields obtained from the inclusive-SR fit, while the two last lines report the yields obtained from the multiple-bin fit. The uncertainty includes both the statistical and systematic uncertainties.
The observed 95% CL exclusion contour for a simplified model of dark-matter production involving an axial-vector operator, Dirac DM and couplings $g_{q}$ = 0.25, $g_{\chi}$ = 1 and $g_{l}$ = 0 as a function of the dark-matter mass $m_{\chi}$ and the mediator mass $m_{\mathrm{med}}$. The plane under the limit curve is excluded.
The expected 95% CL exclusion contour (+1$\sigma$) for a simplified model of dark-matter production involving an axial-vector operator, Dirac DM and couplings $g_{q}$ = 0.25, $g_{\chi}$ = 1 and $g_{l}$ = 0 as a function of the dark-matter mass $m_{\chi}$ and the mediator mass $m_{\mathrm{med}}$. The plane under the limit curve is excluded.
Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the Large Hadron Collider are reported. The data were collected in proton--proton collisions at a centre-of-mass energy of 13 TeV and correspond to an integrated luminosity of 3.2 $\rm fb^{-1}$. The observed data are in agreement with the Standard Model expectations. Exclusion limits are presented in models of new phenomena including pair production of dark matter candidates or large extra spatial dimensions. In a simplified model of dark matter and an axial-vector mediator, the search excludes mediator masses of up to 710 GeV for dark matter candidate masses up to 150 GeV. In an effective theory of dark matter production, values of the suppression scale $M_*$ up to 570 GeV are excluded and the effect of truncation for various coupling values is reported. For the ADD large extra spatial dimension model the search places more stringent limits than earlier searches in the same event topology, excluding $M_{\rm D}$ up to about 2.3 (2.8) TeV for two (six) additional spatial dimensions; the limits are reduced by 20--40% depending on the number of additional spatial dimensions when applying a truncation procedure.
Distribution of missing transverse momentum, reconstructed treating muons as non-interacting particles, in the data and for the background in the 1muCR. The total background expectation is normalized to the post-fit result. Overflows are included in the final bin. The errors include both statistical and systematic uncertainties determined by a bin-by-bin fit.
Distribution of missing transverse momentum, reconstructed treating muons as non-interacting particles, in the data and for the background in the 2muCR. The total background expectation is normalized to the post-fit result. Overflows are included in the final bin. The errors include both statistical and systematic uncertainties determined by a bin-by-bin fit.
Distribution of missing transverse momentum, reconstructed treating electrons as non-interacting particles, in the data and for the background in the 2eleCR. The total background expectation is normalized to the post-fit result. Overflows are included in the final bin. The errors include both statistical and systematic uncertainties determined by a bin-by-bin fit.
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