Search for dark matter produced in association with a single top quark or a top quark pair in proton-proton collisions at s=13 TeV

A search has been performed for heavy resonances decaying to ZZ or ZW in 2l2q final states, with two charged leptons (l = e, mu) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W' bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.A search has been performed for heavy resonances decaying to ZZ or ZW in 2l2q final states, with two charged leptons (l = e, mu) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W' bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.A search for dark matter produced in association with top quarks in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The data set used corresponds to an integrated luminosity of 35.9 fb(-1) recorded with the CMS detector at the LHC. Whereas previous searches for neutral scalar or pseudoscalar mediators considered dark matter production in association with a top quark pair only, this analysis also includes production modes with a single top quark. The results are derived from the combination of multiple selection categories that are defined to target either the single top quark or the top quark pair signature. No significant deviations with respect to the standard model predictions are observed. The results are interpreted in the context of a simplified model in which a scalar or pseudoscalar mediator particle couples to a top quark and subsequently decays into dark matter particles. Scalar and pseudoscalar mediator particles with masses below 290 and 300 GeV, respectively, are excluded at 95% confidence level, assuming a dark matter particle mass of 1 GeV and mediator couplings to fermions and dark matter particles equal to unity.Peer reviewe

Measurement of B_{s}^{0} meson production in pp and PbPb collisions at \sqrt{SNN}

The production cross sections of B_{s}^{0} mesons and charge conjugates are measured in proton-proton (pp) and PbPb collisions via the exclusive decay channel B_{s}^{0}→J/ψϕ→μ^{+}μ^{−}K^{+}K^{−} at a center-of-mass energy of 5.02 TeV per nucleon pair and within the rapidity range |y|<2.4 using the CMS detector at the LHC. The pp measurement is performed as a function of transverse momentum (p_{T}) of the B_{s}^{0} mesons in the range of 7 to 50 GeV/c and is compared to the predictions of perturbative QCD calculations. The B_{s}^{0} production yield in PbPb collisions is measured in two p_{T} intervals, 7 to 15 and 15 to 50 GeV/c, and compared to the yield in pp collisions in the same kinematic region. The nuclear modification factor (R_{AA}) is found to be 1.5±0.6(stat)±0.5(syst) for 7–15 GeV/c, and 0.87±0.30(stat)±0.17(syst) for 15–50 GeV/c, respectively. Within current uncertainties, the B_{s}^{0} results are consistent with models of strangeness enhancement, and suppression by parton energy loss, as observed for the B+ mesons

Measurement of the tt¯ production cross section, the top quark mass, and the strong coupling constant using dilepton events in pp collisions at √s = 13 TeV

A measurement of the top quark–antiquark pair production cross section σtt¯ in proton–proton collisions at a centre-of-mass energy of 13TeV is presented. The data correspond to an integrated luminosity of 35.9fb−1, recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events (e ± μ ∓, μ+μ−, e+e−) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of mMCt=172.5GeV the fit yields a measured cross section σtt¯=803±2(stat)±25(syst)±20(lumi)pb, in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the POWHEG simulation is performed. The measured value of mMCt=172.33±0.14(stat)+0.66−0.72(syst)GeV is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions

Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state with two bquarks and two tau leptons in proton-proton collisions at root s=13 TeV The CMS Collaboration

A search for an exotic decay of the Higgs boson to a pair of light pseudoscalar bosons is performed for the first time in the final state with two b quarks and two tau leptons. The search is motivated in the context of models of physics beyond the standard model (SM), such as two Higgs doublet models extended with a complex scalar singlet (2HDM + S), which include the next-to-minimal supersymmetric SM (NMSSM). The results are based on a data set of proton-proton collisions corresponding to an integrated luminosity of 35.9 fb(-1), accumulated by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV. Masses of the pseudoscalar boson between 15 and 60 GeVare probed, and no excess of events above the SM expectation is observed. Upper limits between 3 and 12% are set on the branching fraction B(h -> aa -> 2 tau 2b) assuming the SM production of the Higgs boson. Upper limits are also set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different 2HDM + S scenarios. Assuming the SM production cross section for the Higgs boson, the upper limit on this quantity is as low as 20% for a mass of the pseudoscalar of 40 GeV in the NMSSM. (C) 2018 The Author(s). Published by Elsevier B.V.Peer reviewe

A Deep Neural Network for Simultaneous Estimation of b Jet Energy and Resolution

We describe a method to obtain point and dispersion estimates for the energies of jets arising from b quarks produced in proton-proton collisions at an energy of s = 13 TeV at the CERN LHC. The algorithm is trained on a large sample of simulated b jets and validated on data recorded by the CMS detector in 2017 corresponding to an integrated luminosity of 41 fb - 1 . A multivariate regression algorithm based on a deep feed-forward neural network employs jet composition and shape information, and the properties of reconstructed secondary vertices associated with the jet. The results of the algorithm are used to improve the sensitivity of analyses that make use of b jets in the final state, such as the observation of Higgs boson decay to b b ¯

Search for contact interactions and large extra dimensions in the dilepton mass spectra from proton-proton collisions at \sqrt{s} = 13 TeV

A search for nonresonant excesses in the invariant mass spectra of electron and muon pairs is presented. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment in 2016, corresponding to a total integrated luminosity of 36 fb^{-1}. No significant deviation from the standard model is observed. Limits are set at 95% confidence level on energy scales for two general classes of nonresonant models. For a class of fermion contact interaction models, lower limits ranging from 20 to 32 TeV are set on the characteristic compositeness scale Λ. For the Arkani-Hamed, Dimopoulos, and Dvali model of large extra dimensions, the first results in the dilepton final state at 13 TeV are reported, and values of the ultraviolet cutoff parameter Λ_{T} below 6.9 TeV are excluded. A combination with recent CMS diphoton results improves this exclusion to Λ_{T} below 7.7 TeV, providing the most sensitive limits to date in nonhadronic final states

Search for the production of W^{\pm} W^{\pm} W^{\mp} events at \sqrt{s} = 13 TeV

A search for the production of events containing three W bosons predicted by the standard model is reported. The search is based on a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the CERN LHC and corresponding to a total integrated luminosity of 35.9 fb^{-1}. The search is performed in final states with three leptons (electrons or muons), or with two same-charge leptons plus two jets. The observed (expected) significance of the signal for W^{\pm} W^{\pm} W^{\mp} production is 0.60 (1.78) standard deviations, and the ratio of the measured signal yield to that expected from the standard model is 0.34_{-0.34}^{+0.62}. Limits are placed on three anomalous quartic gauge couplings and on the production of massive axionlike particles

Measurement of the energy density as a function of pseudorapidity in proton-proton collisions at root \sqrt{s} = 13 TeV

A measurement of the energy density in proton–proton collisions at a centre-of-mass energy of s√=13 TeV is presented. The data have been recorded with the CMS experiment at the LHC during low luminosity operations in 2015. The energy density is studied as a function of pseudorapidity in the ranges −6.6<η<−5.2 and 3.15<|η|<5.20. The results are compared with the predictions of several models. All the models considered suggest a different shape of the pseudorapidity dependence compared to that observed in the data. A comparison with LHC proton–proton collision data at s√=0.9 and 7TeV confirms the compatibility of the data with the hypothesis of limiting fragmentation

Constraints on anomalous HVV couplings from the production of Higgs bosons decaying to τ lepton pairs

A study is presented of anomalous HVV interactions of the Higgs boson, including its CP properties. The study uses Higgs boson candidates produced mainly in vector boson fusion and gluon fusion that subsequently decay to a pair of τ leptons. The data were recorded by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 35.9  fb−1. A matrix element technique is employed for the analysis of anomalous interactions. The results are combined with those from the H→4ℓ decay channel presented earlier, yielding the most stringent constraints on anomalous Higgs boson couplings to electroweak vector bosons expressed as effective cross section fractions and phases: the CP-violating parameter fa3cos(ϕa3)=(0.00±0.27)×10−3 and the CP-conserving parameters fa2cos(ϕa2)=(0.08+1.04−0.21)×10−3, fΛ1cos(ϕΛ1)=(0.00+0.53−0.09)×10−3, and fZγΛ1cos(ϕZγΛ1)=(0.0+1.1−1.3)×10−3. The current dataset does not allow for precise constraints on CP properties in the gluon fusion process. The results are consistent with standard model expectations

Search for resonant production of second-generation sleptons with same-sign dimuon events in proton-proton collisions at root s=13 TeV

A search is presented for resonant production of second-generation sleptons ( μ˜L , ν˜μ ) via the R-parity-violating coupling λ′211 to quarks, in events with two same-sign muons and at least two jets in the final state. The smuon (muon sneutrino) is expected to decay into a muon and a neutralino (chargino), which will then decay into a second muon and at least two jets. The analysis is based on the 2016 data set of proton-proton collisions at s√=13TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb−1 . No significant deviation is observed with respect to standard model expectations. Upper limits on cross sections, ranging from 0.24 to 730 fb , are derived in the context of two simplified models representing the dominant signal contributions leading to a same-sign muon pair. The cross section limits are translated into coupling limits for a modified constrained minimal supersymmetric model with λ′211 as the only nonzero R-parity violating coupling. The results significantly extend restrictions of the parameter space compared with previous searches for similar models