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.
The first measurement of the $Z$ boson production cross-section at centre-of-mass energy $\sqrt{s} = 5.02\,$TeV in the forward region is reported, using $pp$ collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of $100 \pm 2\,\rm{pb^{-1}}$. The production cross-section is measured for final-state muons in the pseudorapidity range $2.0<\eta<4.5$ with transverse momentum $p_{\rm{T}}> 20\,\rm{GeV/}\it{c}$. The integrated cross-section is determined to be \[ \sigma_{Z \rightarrow \mu^{+}\mu^{-}} = 39.6 \pm 0.7\,(\rm{stat}) \pm 0.6\,(\rm{syst}) \pm 0.8\,(\rm{lumi}) \ \rm{pb} \] for the di-muon invariant mass in the range $60<M_{\mu\mu}<120\,\rm{GeV/}\it{c^{2}}$. This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling. Based on a previous LHCb measurement of the $Z$ boson production cross-section in $p$Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV, the nuclear modification factor $R_{p\rm{Pb}}$ is measured for the first time at this energy. The measured values are $1.2^{+0.5}_{-0.3}\,(\rm{stat}) \pm 0.1\,(\rm{syst})$ in the forward region ($1.53<y^*_{\mu}<4.03$) and $3.6^{+1.6}_{-0.9}\,(\rm{stat}) \pm 0.2\,(\rm{syst})$ in the backward region ($-4.97<y^*_{\mu}<-2.47$), where $y^*_{\mu}$ represents the muon rapidity in the centre-of-mass frame.
Systematic uncertainties on the single differential cross-sections in bins of $y^{Z}$, presented in percentage.
Systematic uncertainties on the single differential cross-sections in bins of $p_{T}^{Z}$, presented in percentage.
Systematic uncertainties on the single differential cross-sections in bins of $\phi_{\eta}^{*}$, presented in percentage.
A search is presented for a third-generation leptoquark (LQ) coupled exclusively to a $\tau$ lepton and a b quark. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector, corresponding to an integrated luminosity of 138 fb$^{-1}$. Events with $\tau$ leptons and a varying number of jets originating from b quarks are considered, targeting the single and pair production of LQs, as well as nonresonant $t$-channel LQ exchange. An excess is observed in the data with respect to the background expectation in the combined analysis of all search regions. For a benchmark LQ mass of 2 TeV and an LQ-b-$\tau$ coupling strength of 2.5, the excess reaches a local significance of up to 2.8 standard deviations. Upper limits at the 95% confidence level are placed on the LQ production cross section in the LQ mass range 0.5-2.3 TeV, and up to 3 TeV for $t$-channel LQ exchange. Leptoquarks are excluded below masses of 1.22-1.88 TeV for different LQ models and varying coupling strengths up to 2.5. The study of nonresonant $\tau\tau$ production through $t$-channel LQ exchange allows lower limits on the LQ mass of up to 2.3 TeV to be obtained.
Product of acceptance and efficiency of a vector LQ signal as a function of LQ mass under the assumption of exclusive LQ couplings to b quarks and $\tau$ leptons. The acceptances and efficiencies are restricted to the sensitive region of $S_\mathrm{T}^\mathrm{MET} > 800\,\mathrm{GeV}$ and are computed with respect to all possible decay modes of two $\tau$ leptons.
Product of acceptance and efficiency of a vector LQ signal as a function of LQ mass under the assumption of exclusive LQ couplings to b quarks and $\tau$ leptons. The acceptances and efficiencies are restricted to the sensitive region of $\chi < 4$ and are computed with respect to all possible decay modes of two $\tau$ leptons.
Postfit distributions of $S_\mathrm{T}^\mathrm{MET}$ in the $\mathrm{e}\mu$ channel of the 0b category for the combined 2016-2018 data set after a simultaneous fit of the background and vector LQ signal to the data. The number of events in each bin are divided by the respective bin width. The last bin includes the overflow.
The first search for scalar leptoquarks produced in $\tau$-lepton-quark collisions is presented. It is based on a set of proton-proton collision data recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb$^{-1}$. The reconstructed final state consists of a jet, significant missing transverse momentum, and a $\tau$ lepton reconstructed through its hadronic or leptonic decays. Limits are set on the product of the leptoquark production cross section and branching fraction and interpreted as exclusions in the plane of the leptoquark mass and the leptoquark-$\tau$-quark coupling strength.
Observed and expected distributions of the collinear mass in the $\tau_\mathrm{h}$+jet btag category with the BDT requirements selecting the most signal-like events. The signal hypothesis corresponds to a scalar leptoquark coupled to u quarks and $\tau$ leptons with a coupling strength $\lambda$ equal to 1.5.
Observed and expected distributions of the collinear mass in the e+jet btag category with the BDT requirements selecting the most signal-like events. The signal hypothesis corresponds to a scalar leptoquark coupled to u quarks and $\tau$ leptons with a coupling strength $\lambda$ equal to 1.5.
Observed and expected distributions of the collinear mass in the $\mu$+jet btag category with the BDT requirements selecting the most signal-like events. The signal hypothesis corresponds to a scalar leptoquark coupled to u quarks and $\tau$ leptons with a coupling strength $\lambda$ equal to 1.5.
The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton-proton collisions at a center-of-mass energy of 13 TeV. The analysis uses a data sample corresponding to a total integrated luminosity of 138 fb$^{-1}$ collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The W+c production cross section and the cross section ratio $R^\pm_\text{c}$ = $\sigma$(W$^+$+$\bar{\text{c}}$) / $\sigma$(W$^-$+$\text{c}$) are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in $R^\pm_\text{c}$. The precision of the measurements is improved with respect to previous studies, reaching 1% in $R^\pm_\text{c}$ = 0.950 $\pm$ 0.005 (stat) $\pm$ 0.010 (syst). The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics.
Particle level efficiency*acceptance correction factors and cross section measurements for the four channels (W decay to muon or electron and charm identification via muon or secondary vertex inside a jet). The combined measurement is shown in the last row.
Parton level efficiency*acceptance correction factors and cross section measurements for the four channels (W decay to muon or electron and charm identification via muon or secondary vertex inside a jet). The combined measurement is shown in the last row.
Inclusive cross section predictions at QCD NLO accuracy from MCFM using different PDF sets
A measurement of the Higgs boson (H) production via vector boson fusion (VBF) and its decay into a bottom quark-antiquark pair ($\mathrm{b\bar{b}}$) is presented using proton-proton collision data recorded by the CMS experiment at $\sqrt{s}$ = 13 TeV and corresponding to an integrated luminosity of 90.8 fb$^{-1}$. Treating the gluon-gluon fusion process as a background and constraining its rate to the value expected in the standard model (SM) within uncertainties, the signal strength of the VBF process, defined as the ratio of the observed signal rate to that predicted by the SM, is measured to be $\mu^\text{qqH}_\mathrm{Hb\bar{b}}$ = 1.01 $^{+0.55}_{-0.46}$. The VBF signal is observed with a significance of 2.4 standard deviations relative to the background prediction, while the expected significance is 2.7 standard deviations. Considering inclusive Higgs boson production and decay into bottom quarks, the signal strength is measured to be $\mu^\text{incl.}_\mathrm{Hb\bar{b}}$ = 0.99 $^{+0.48}_{-0.41}$, corresponding to an observed (expected) significance of 2.6 (2.9) standard deviations.
The mbb distribution after weighted combination of all categories in the analysis weighted with S/(S + B). where S is the total Hbb signal yield (both VBF and ggH) and B is the total background yield including QCD multijet and Z+jets
The best fit values of the signal strength modifier for the different processes. The uncertainties, corresponding to one standard deviation confidence intervals, include both statistical and systematic sources. The additional breakdown of the uncertainties into their separate statistical and systematic contributions is also shown.
The best fit values of the signal strength modifier for the different processes by floating the VBF and ggH production rates independently. The uncertainties, corresponding to one standard deviation confidence intervals, include both statistical and systematic sources. The additional breakdown of the uncertainties into their separate statistical and systematic contributions is also shown.
A search for new physics in final states consisting of at least one photon, multiple jets, and large missing transverse momentum is presented, using proton-proton collision events at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 137 fb$^{-1}$, recorded by the CMS experiment at the CERN LHC from 2016 to 2018. The events are divided into mutually exclusive bins characterized by the missing transverse momentum, the number of jets, the number of b-tagged jets, and jets consistent with the presence of hadronically decaying W, Z, or Higgs bosons. The observed data are found to be consistent with the prediction from standard model processes. The results are interpreted in the context of simplified models of pair production of supersymmetric particles via strong and electroweak interactions. Depending on the details of the signal models, gluinos and squarks of masses up to 2.35 and 1.43 TeV, respectively, and electroweakinos of masses up to 1.23 TeV are excluded at 95% confidence level.
SM background predictions, data observations and signal yields in the signal region.
The 95% CL observed upper limits on the production cross sections for $m_{\tilde{g}}$ in T5bbbbZg.
Gluino - neutralino mass points lying on the observed exclusion contour of T5bbbbZg model.
A search for new physics in top quark production with additional final-state leptons is performed using data collected by the CMS experiment in proton-proton collisions at $\sqrt{s}$ = 13 TeV at the LHC during 2016-2018. The data set corresponds to an integrated luminosity of 138 fb$^{-1}$. Using the framework of effective field theory (EFT), potential new physics effects are parametrized in terms of 26 dimension-six EFT operators. The impacts of EFT operators are incorporated through the event-level reweighting of Monte Carlo simulations, which allows for detector-level predictions. The events are divided into several categories based on lepton multiplicity, total lepton charge, jet multiplicity, and b-tagged jet multiplicity. Kinematic variables corresponding to the transverse momentum ($p_\mathrm{T}$) of the leading pair of leptons and/or jets as well as the $p_\mathrm{T}$ of on-shell Z bosons are used to extract the 95% confidence intervals of the 26 Wilson coefficients corresponding to these EFT operators. No significant deviation with respect to the standard model prediction is found.
The 1$\sigma$ and 2$\sigma$ uncertainty intervals extracted from the likelihood fits described in Section 7. The intervals are shown for the case where the other WCs are profiled, and the case where the other WCs are fixed to their SM values of zero.
Observed $2 \Delta NLL$ of a 2D scan for $c_{tW}$ and $c_{tZ}$ with the other WCs profiled.
Observed $2 \Delta NLL$ of a 2D scan for $c_{tW}$ and $c_{tZ}$ with the other WCs fixed to their SM values.
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.
Measurements of the charge-dependent two-particle angular correlation function in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_\mathrm{NN}}$ = 8.16 TeV and lead-lead (PbPb) collisions at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV are reported. The pPb and PbPb data sets correspond to integrated luminosities of 186 nb$^{-1}$ and 0.607 nb$^{-1}$, respectively, and were collected using the CMS detector at the CERN LHC. The charge-dependent correlations are characterized by balance functions of same- and opposite-sign particle pairs. The balance functions, which contain information about the creation time of charged particle pairs and the development of collectivity, are studied as functions of relative pseudorapidity ($\Delta \eta$) and relative azimuthal angle ($\Delta \phi$), for various multiplicity and transverse momentum ($p_\mathrm{T}$) intervals. A multiplicity dependence of the balance function is observed in $\Delta \eta$ and $\Delta \phi$ for both systems. The width of the balance functions decreases toward high-multiplicity collisions in the momentum region $\lt$ 2 GeV, for pPb and PbPb results. Integrals of the balance functions are presented in both systems, and a mild dependence of the charge-balancing fractions on multiplicity is observed. No multiplicity dependence is observed at higher transverse momentum. The data are compared with HYDJET, HIJING and AMPT generator predictions, none of which capture completely the multiplicity dependence seen in the data. The comparison of results with different center-of-mass energies suggest that the balance functions become narrower at higher energies, which is consistent with the idea of delayed hadronization and the effect of radial flow.
$\Delta\eta$ projection of balance function in low $p_{T}$ in 0-10% centrality
$\Delta\eta$ projection of balance function in low $p_{T}$ in 30-40% centrality
$\Delta\eta$ projection of balance function in low $p_{T}$ in 70-80% centrality
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