Differential and double-differential cross sections for the production of top quark pairs in proton-proton collisions at s=13 TeV are measured as a function of kinematic variables of the top quarks ...and the top quark-antiquark (tt¯) system. In addition, kinematic variables and multiplicities of jets associated with the tt¯ production are measured. This analysis is based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.8 fb−1. The measurements are performed in the lepton+jets decay channels with a single muon or electron and jets in the final state. The differential cross sections are presented at the particle level, within a phase space close to the experimental acceptance, and at the parton level in the full phase space. The results are compared to several standard model predictions that use different methods and approximations. The kinematic variables of the top quarks and the tt¯ system are reasonably described in general, though none predict all the measured distributions. In particular, the transverse momentum distribution of the top quarks is more steeply falling than predicted. The kinematic distributions and multiplicities of jets are adequately modeled by certain combinations of next-to-leading-order calculations and parton shower models.
A search for resonancelike structures in the B0sπ± invariant mass spectrum is performed using proton-proton collision data collected by the CMS experiment at the LHC at √s = 8 TeV , corresponding to ...an integrated luminosity of 19.7 fb−1. The B0s mesons are reconstructed in the decay chain B0s → J/ψϕ, with J/ψ → μ+μ− and ϕ → K+K−. The B0sπ± invariant mass distribution shows no statistically significant peaks for different selection requirements on the reconstructed B0s and π± candidates. Upper limits are set on the relative production rates of the X(5568) and B0s states times the branching fraction of the decay X(5568) ± → B0sπ±. In addition, upper limits are obtained as a function of the mass and the natural width of possible exotic states decaying into B0sπ±.
The prompt D0 meson azimuthal anisotropy coefficients, v2 and v3, are measured at midrapidity (|y| < 1.0) in Pb-Pb collisions at a center-of-mass energy √sNN = 5.02 TeV per nucleon pair with data ...collected by the CMS experiment. The measurement is performed in the transverse momentum (pT) range of 1 to 40 GeV/c, for central and midcentral collisions. The v2 coefficient is found to be positive throughout the pT range studied. The first measurement of the prompt D0 meson v3 coefficient is performed, and values up to 0.07 are observed for pT around 4 GeV/c. Compared to measurements of charged particles, a similar pT dependence, but smaller magnitude for pT < 6 GeV/c, is found for prompt D0 meson v2 and v3 coefficients. The results are consistent with the presence of collective motion of charm quarks at low pT and a path length dependence of charm quark energy loss at high pT, thereby providing new constraints on the theoretical description of the interactions between charm quarks and the quark-gluon plasma.
Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not ...known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.
The relative yields of Υ mesons produced in pp and Pb-Pb collisions at √sNN = 5.02 TeV and reconstructed via the dimuon decay channel are measured using data collected by the CMS experiment. Double ...ratios are formed by comparing the yields of the excited states, Υ(2S) and Υ(3S), to the ground state, Υ(1S), in both Pb-Pb and p p collisions at the same center-of-mass energy. The double ratios, Υ(nS)/Υ(1S)Pb−Pb/Υ(nS)/Υ(1S)pp, are measured to be 0.308 ± 0.055 (stat) ± 0.019 (syst) for the Υ(2S) and less than 0.26 at 95% confidence level for the Υ(3S). No significant Υ(3S) signal is found in the Pb-Pb data. The double ratios are studied as a function of collision centrality, as well as Υ transverse momentum and rapidity. No significant dependencies are observed.
Results are reported from a search for new physics in 13 TeV proton-proton collisions in the final state with large missing transverse momentum and two Higgs bosons decaying via H→bb¯. The search ...uses a data sample accumulated by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb−1. The search is motivated by models based on gauge-mediated supersymmetry breaking, which predict the electroweak production of a pair of Higgsinos, each of which can decay via a cascade process to a Higgs boson and an undetected lightest supersymmetric particle. The observed event yields in the signal regions are consistent with the standard model background expectation obtained from control regions in data. Higgsinos in the mass range 230–770 GeV are excluded at 95% confidence level in the context of a simplified model for the production and decay of approximately degenerate Higgsinos.
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 √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 pT of the Z boson and pT 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 pT > 10 GeV, at least one lepton with pT > 26 GeV, and a mass of the pair in the range 71–111 GeV, while the charm jet is required to have pT > 30 GeV and |η| < 2.4. These are the first measurements of these cross sections in proton-proton collisions at 13 TeV.
