16 Search Results

Production cross sections of Image 1, Image 2, and Image 3 states decaying into Image 4 in proton-lead ( $\mathrm{p}\mathrm{Pb}$ ) collisions are reported using data collected by the CMS experiment at $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02\text{TeV}$ . A comparison is made with corresponding cross sections obtained with $\mathrm{p}\mathrm{p}$ data measured at the same collision energy and scaled by the Pb nucleus mass number. The nuclear modification factor for Image 1 ismore » found to be Image 5. Similar results for the excited states indicate a sequential suppression pattern, such that Image 6. The suppression of all states is much less pronounced in $\mathrm{p}\mathrm{Pb}$ than in PbPb collisions, and independent of transverse momentum Image 7 and center-of-mass rapidity Image 8 of the individual Image 9 state in the studied range Image 10 and Image 11. Models that incorporate final-state effects of bottomonia in pPb collisions are in better agreement with the data than those which only assume initial-state modifications.« 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

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

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

A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb$$^{−1}$$, recorded at a center-of-mass energy of 13 TeV in 2016–2018. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is setmore » on the product of the cross section for production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level.[graphic not available: see fulltext]« less

A search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at $$ \sqrt{s} $$ = 13 TeV, corresponding to an integrated luminosity of 35.9 fb$$^{−1}$$, collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H → aa → μμττ, and considers pseudoscalar masses in the range 3.6 < m$$_{a}$$< 21 GeV. Because of the large mass difference between the H and the a bosons and the smallmore » masses of the a boson decay products, both the μμ and the ττ pairs have high Lorentz boost and are collimated. The ττ reconstruction efficiency is increased by modifying the standard technique for hadronic τ lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of m$$_{a}$$, on the branching fraction (ℬ) for H → aa → μμττ, down to 1.5 (2.0) × 10$$^{−4}$$ for m$$_{H}$$ = 125 (300) GeV. Model-dependent limits on ℬ(H → aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV.[graphic not available: see fulltext]« less

The momentum-weighted sum of the electric charges of particles inside a jet, known as jet charge, is sensitive to the electric charge of the particle initiating the parton shower. This paper presents jet charge distributions in $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV lead-lead (PbPb) and proton-proton (pp) collisions recorded with the CMS detector at the LHC. These data correspond to integrated luminosities of 404 μb$$^{−1}$$ and 27.4 pb$$^{−1}$$ for PbPb and pp collisions, respectively. Leveraging the sensitivity of the jet charge to fundamental differences in the electric charges of quarks and gluons, the jet charge distributions from simulated events aremore » used as templates to extract the quark- and gluon-like jet fractions from data. The modification of these jet fractions is examined by comparing pp and PbPb data as a function of the overlap of the colliding Pb nuclei (centrality). This measurement tests the color charge dependence of jet energy loss due to interactions with the quark-gluon plasma. No significant modification between different centrality classes and with respect to pp results is observed in the extracted quark- and gluon-like jet fractions.[graphic not available: see fulltext]« less

Results are presented from a search for events containing an excited lepton (electron or muon) produced in association with an ordinary lepton of the same flavor and decaying to a lepton and two hadronic jets. Both the production and the decay of the excited leptons are assumed to occur via a contact interaction with a characteristic energy scale Λ. The branching fraction for the decay mode under study increases with the mass of the excited lepton and is the most sensitive channel for very heavy excited leptons. The analysis uses a sample of proton-proton collisions collected by the CMS experimentmore » at the LHC at $$ \sqrt{s} $$ = 13 TeV, corresponding to an integrated luminosity of 77.4 fb$$^{−1}$$. The four-body invariant mass of the two lepton plus two jet system is used as the primary discriminating variable. No significant excess of events beyond the expectation for standard model processes is observed. Assuming that Λ is equal to the mass of the excited leptons, excited electrons and muons with masses below 5.6 and 5.7 TeV, respectively, are excluded at 95% confidence level. These are the best limits to date.[graphic not available: see fulltext]« less

This paper reports on a search for an extension to the scalar sector of the standard model, where a new CP-even (odd) boson decays to a Z boson and a lighter CP-odd (even) boson, and the latter further decays to a b quark pair. The Z boson is reconstructed via its decays to electron or muon pairs. The analysed data were recorded in proton-proton collisions at a center-of-mass energy $$ \sqrt{s} $$ = 13 TeV, collected by the CMS experiment at the LHC during 2016, corresponding to an integrated luminosity of 35.9 fb$$^{−1}$$. Data and predictions from the standard modelmore » are in agreement within the uncertainties. Upper limits at 95% confidence level are set on the production cross section times branching fraction, with masses of the new bosons up to 1000 GeV. The results are interpreted in the context of the two-Higgs-doublet model.[graphic not available: see fulltext]« less

The production of a $${\text {Z}}$$ boson, decaying to two charged leptons, in association with jets in proton-proton collisions at a centre-of-mass energy of 13 $$\,\text {TeV}$$ is measured. Data recorded with the CMS detector at the LHC are used that correspond to an integrated luminosity of 2.19 $$\,\text {fb}^\text {-1}$$ . The cross section is measured as a function of the jet multiplicity and its dependence on the transverse momentum of the $${\text {Z}}$$ boson, the jet kinematic variables (transverse momentum and rapidity), the scalar sum of the jet momenta, which quantifies the hadronic activity, and the balance inmore » transverse momentum between the reconstructed jet recoil and the $${\text {Z}}$$ boson. The measurements are compared with predictions from four different calculations. The first two merge matrix elements with different parton multiplicities in the final state and parton showering, one of which includes one-loop corrections. The third is a fixed-order calculation with next-to-next-to-leading order accuracy for the process with a $${\text {Z}}$$ boson and one parton in the final state. The fourth combines the fully differential next-to-next-to-leading order calculation of the process with no parton in the final state with next-to-next-to-leading logarithm resummation and parton showering.« less