227 Search Results

We present the first study of charged-hadron production associated with jets originating from b quarks in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data sample used in this study was collected with the CMS detector at the CERN LHC and corresponds to an integrated luminosity of 27.4 pb$$^{−1}$$. To characterize the jet substructure, the differential jet shapes, defined as the normalized transverse momentum distribution of charged hadrons as a function of angular distance from the jet axis, are measured for b jets. In addition to the jet shapes, the per-jet yields of charged particles associated with bmore » jets are also quantified, again as a function of the angular distance with respect to the jet axis. Extracted jet shape and particle yield distributions for b jets are compared with results for inclusive jets, as well as with the predictions from the pythia and herwig++ event generators.[graphic not available: see fulltext]« less

The rate for Higgs ($${\mathrm{H}} $$) bosons production in association with either one ($${\mathrm{t}} {\mathrm{H}} $$) or two ($${\mathrm{t}} {{\overline{{{\mathrm{t}}}}}} {\mathrm{H}} $$) top quarks is measured in final states containing multiple electrons, muons, or tau leptons decaying to hadrons and a neutrino, using proton–proton collisions recorded at a center-of-mass energy of $$13\,\text {Te}\text {V} $$ by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137$$\,\text {fb}^{-1}$$. The analysis is aimed at events that contain $${\mathrm{H}} \rightarrow {\mathrm{W}} {\mathrm{W}} $$, $${\mathrm{H}} \rightarrow {\tau } {\tau } $$, or $${\mathrm{H}} \rightarrow {\mathrm{Z}} {\mathrm{Z}} $$ decays and each ofmore » the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among $${\mathrm{t}} {\mathrm{H}} $$, $${\mathrm{t}} {{\overline{{{\mathrm{t}}}}}} {\mathrm{H}} $$, and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the $${\mathrm{t}} {{\overline{{{\mathrm{t}}}}}} {\mathrm{H}} $$ and $${\mathrm{t}} {\mathrm{H}} $$ signals correspond to $$0.92 \pm 0.19\,\text {(stat)} ^{+0.17}_{-0.13}\,\text {(syst)} $$ and $$5.7 \pm 2.7\,\text {(stat)} \pm 3.0\,\text {(syst)} $$ of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for $${\mathrm{t}} {{\overline{{{\mathrm{t}}}}}} {\mathrm{H}} $$, and to 1.4 (0.3) for $${\mathrm{t}} {\mathrm{H}} $$ production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling $$y_{{\mathrm{t}}}$$ of the Higgs boson to the top quark divided by its SM expectation, $$\kappa _{{\mathrm{t}}}=y_{{\mathrm{t}}}/y_{{\mathrm{t}}}^{\mathrm {SM}}$$, is constrained to be within $$-0.9< \kappa _{{\mathrm{t}}}< -0.7$$ or $$0.7< \kappa _{{\mathrm{t}}}< 1.1$$, at 95% confidence level. This result is the most sensitive measurement of the $${\mathrm{t}} {{\overline{{{\mathrm{t}}}}}} {\mathrm{H}} $$ production rate to date.« less

Angular distributions of the decay B$$^{+}$$→ K$$^{∗}$$(892)$$^{+}$$μ$$^{+}$$μ$$^{−}$$ are studied using events collected with the CMS detector in $$ \sqrt{\mathrm{s}} $$ = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb$$^{−1}$$. The forward-backward asymmetry of the muons and the longitudinal polarization of the K$$^{∗}$$(892)$$^{+}$$ meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction.[graphic not available: see fulltext]

A search for phenomena beyond the standard model in final states with two oppositely charged same-flavor leptons and missing transverse momentum is presented. The search uses a data sample of proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV, corresponding to an integrated luminosity of 137 fb$$^{−1}$$, collected by the CMS experiment at the LHC. Three potential signatures of physics beyond the standard model are explored: an excess of events with a lepton pair, whose invariant mass is consistent with the Z boson mass; a kinematic edge in the invariant mass distribution of the lepton pair; and the nonresonant productionmore » of two leptons. The observed event yields are consistent with those expected from standard model backgrounds. The results of the first search allow the exclusion of gluino masses up to 1870 GeV, as well as chargino (neutralino) masses up to 750 (800) GeV, while those of the searches for the other two signatures allow the exclusion of light-flavor (bottom) squark masses up to 1800 (1600) GeV and slepton masses up to 700 GeV, respectively, at 95% confidence level within certain supersymmetry scenarios.[graphic not available: see fulltext]« less

Measurements are presented of differential cross sections for the production of Z bosons in association with at least one jet initiated by a charm quark in pp collisions at $$ \sqrt{s} $$ = 13 TeV. The data recorded by the CMS experiment at the LHC correspond to an integrated luminosity of 35.9 fb$$^{−1}$$. The final states contain a pair of electrons or muons that are the decay products of a Z boson, and a jet consistent with being initiated by a charm quark produced in the hard interaction. Differential cross sections as a function of the transverse momentum p$$_{T}$$ ofmore » the Z boson and p$$_{T}$$ of the charm jet are compared with predictions from Monte Carlo event generators. The inclusive production cross section 405.4 ± 5.6 (stat) ± 24.3 (exp) ± 3.7 (theo) pb, is measured in a fiducial region requiring both leptons to have pseudorapidity |η| < 2.4 and p$$_{T}$$> 10 GeV, at least one lepton with p$$_{T}$$> 26 GeV, and a mass of the pair in the range 71–111 GeV, while the charm jet is required to have p$$_{T}$$> 30 GeV and |η| < 2.4. These are the first measurements of these cross sections in proton-proton collisions at 13 TeV.[graphic not available: see fulltext]« less

This paper presents new sets of parameters (“tunes”) for the underlying-event model of the $${\textsc {herwig}} \,7$$ event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in $${\textsc {herwig}} \,7$$, and are obtained from a fit to minimum-bias data collected by the CMS experiment at $$\sqrt{s}=0.9$$, 7, and $$13 \,\text {Te}\text {V} $$. The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for eventmore » shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.« less

A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of $$ \sqrt{s} $$ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$$^{−1}$$. No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into $$ \gamma \gamma \mathrm{b}\overline{\mathrm{b}} $$.more » The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κ$$_{λ}$$ and the coupling between a pair of Higgs bosons and a pair of vector bosons c$$_{2V}$$ are constrained within the ranges −3.3 < κ$$_{λ}$$< 8.5 and −1.3 < c$$_{2V}$$< 3.5 at 95% confidence level. Constraints on κ$$_{λ}$$ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κ$$_{λ}$$ and the top quark Yukawa coupling modifier κ$$_{t}$$.[graphic not available: see fulltext]« less

Events containing one or more top quarks produced with additional prompt leptons are used to search for new physics within the framework of an effective field theory (EFT). The data correspond to an integrated luminosity of 41.5 fb$$^{−1}$$ of proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, collected by the CMS experiment in 2017. The selected events are required to have either two leptons with the same charge or more than two leptons; jets, including identified bottom quark jets, are also required, and the selected events are divided into categories based on the multiplicities of thesemore » objects. Sixteen dimension-six operators that can affect processes involving top quarks produced with additional charged leptons are considered in this analysis. Constructed to target EFT effects directly, the analysis applies a novel approach in which the observed yields are parameterized in terms of the Wilson coefficients (WCs) of the EFT operators. A simultaneous fit of the 16 WCs to the data is performed and two standard deviation confidence intervals for the WCs are extracted; the standard model expectations for the WC values are within these intervals for all of the WCs probed.[graphic not available: see fulltext]« less

The CP -violating weak phase ${\varphi }_{\mathrm{s}}$ and the decay width difference $\mathrm{\Delta }{\mathrm{\Gamma }}_{\mathrm{s}}$ between the light and heavy ${\mathrm{B}}_s^0$ mass eigenstates are measured with the CMS detector at the LHC in a sample of $48500$ reconstructed ${\mathrm{B}}_s^0\to \mathrm{J}/\mathrm{\psi }\mathrm{\varphi }\left(1020\right)\to {\mathrm{\mu }}^{+more »}$ μ − K + K − events. The measurement is based on a data sample corresponding to an integrated luminosity of $96.4{\text{fb}}^{-1}$ , collected in proton-proton collisions at $\sqrt{s}=13\text{TeV}$ in 2017–2018. To extract the values of ${\varphi }_{\mathrm{s}}$ and $\mathrm{\Delta }{\mathrm{\Gamma }}_{\mathrm{s}}$ , a time-dependent and flavor-tagged angular analysis of the ${\mathrm{\mu }}^{+}{\mathrm{\mu }}^{-}{\mathrm{K}}^{+}{\mathrm{K}}^{-}$ final state is performed. The analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on machine learning techniques. The measurement yields ${\varphi }_{\mathrm{s}}=-11\pm 50\text{(stat)}\pm 10\text{(syst)}\text{mrad}$ and $\mathrm{\Delta }{\mathrm{\Gamma }}_{\mathrm{s}}=0.114\pm 0.014\text{(stat)}\pm 0.007\text{(syst)}{\text{ps}}^{-1}$ , in agreement with the standard model predictions. When combined with the previous CMS measurement at $\sqrt{s}=8\text{TeV}$ , the following values are obtained: ${\varphi }_{\mathrm{s}}=-21\pm 44\text{(stat)}\pm 10\text{(syst)}\text{mrad}$ , $\mathrm{\Delta }{\mathrm{\Gamma }}_{\mathrm{s}}=0.1032\pm 0.0095\text{(stat)}\pm 0.0048\text{(syst)}{\text{ps}}^{-1}$ , a significant improvement over the 8 TeV result.« less

Measurements of the fiducial inclusive and differential production cross sections of the Higgs boson in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV are performed using events where the Higgs boson decays into a pair of W bosons that subsequently decay into a final state with an electron, a muon, and a pair of neutrinos. The analysis is based on data collected with the CMS detector at the LHC during 2016–2018, corresponding to an integrated luminosity of 137 fb$$^{−1}$$. Production cross sections are measured as a function of the transverse momentum of the Higgs boson and the associated jetmore » multiplicity. The Higgs boson signal is extracted and simultaneously unfolded to correct for selection efficiency and resolution effects using maximum-likelihood fits to the observed distributions in data. The integrated fiducial cross section is measured to be 86.5 ± 9.5 fb, consistent with the Standard Model expectation of 82.5 ± 4.2 fb. No significant deviation from the Standard Model expectations is observed in the differential measurements.[graphic not available: see fulltext]« less