A search is presented for the associated production of a standard model Higgs boson with a top quark-antiquark pair ( $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ ), in which the Higgs boson decays ...into a b quark-antiquark pair, in proton-proton collisions at a centre-of-mass energy $ \sqrt{s}=13 $ TeV. The data correspond to an integrated luminosity of 35.9 fb$^{−1}$ recorded with the CMS detector at the CERN LHC. Candidate $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ events are selected that contain either one or two electrons or muons from the $ \mathrm{t}\overline{\mathrm{t}} $ decays and are categorised according to the number of jets. Multivariate techniques are employed to further classify the events and eventually discriminate between signal and background. The results are characterised by an observed $ \mathrm{t}\overline{\mathrm{t}}\mathrm{H} $ signal strength relative to the standard model cross section, μ = σ/σ$_{SM}$, under the assumption of a Higgs boson mass of 125 GeV. A combined fit of multivariate discriminant distributions in all categories results in an observed (expected) upper limit on μ of 1.5 (0.9) at 95% confidence level, and a best fit value of 0.72 ± 0.24(stat) ± 0.38(syst), corresponding to an observed (expected) signal significance of 1.6 (2.2) standard deviations above the background-only hypothesis.
A study of the $ {\mathrm{B}}^{+}\to \mathrm{J}/\psi \overline{\Lambda}\mathrm{p} $ decay using proton-proton collision data collected at $ \sqrt{s} $ = 8 TeV by the CMS experiment at the LHC, ...corresponding to an integrated luminosity of 19.6 fb$^{−1}$, is presented. The ratio of branching fractions $ \mathcal{B}\left({\mathrm{B}}^{+}\to \mathrm{J}/\psi \overline{\Lambda}\mathrm{p}\right)/\mathcal{B}\left({\mathrm{B}}^{+}\to \mathrm{J}/{\psi \mathrm{K}}^{\ast }{(892)}^{+}\right) $ is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011($ \mathcal{B} $))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of $ \overline{\Lambda} $ and K$^{*}$(892)$^{+}$ decays to reconstructed final states. The invariant mass distributions of the $ \mathrm{J}/\psi \overline{\Lambda} $, J/ψp, and $ \overline{\Lambda}\mathrm{p} $ systems produced in the $ {\mathrm{B}}^{+}\to \mathrm{J}/\psi \overline{\varLambda}\mathrm{p} $ decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the observed invariant mass distributions are consistent with the contributions from excited kaons decaying to the $ \overline{\Lambda}\mathrm{p} $ system.
Results of a search for nonresonant production of Higgs boson pairs, with each Higgs boson decaying to a $ \mathrm{b}\overline{\mathrm{b}} $ pair, are presented. This search uses data from ...proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{−1}$, collected by the CMS detector at the LHC. No signal is observed, and a 95% confidence level upper limit of 847 fb is set on the cross section for standard model nonresonant Higgs boson pair production times the squared branching fraction of the Higgs boson decay to a $ \mathrm{b}\overline{\mathrm{b}} $ pair. The same signature is studied, and upper limits are set, in the context of models of physics beyond the standard model that predict modified couplings of the Higgs boson.
The WZ production cross section is measured in proton-proton collisions at a centre-of-mass energy $ \sqrt{s} $ = 13 TeV using data collected with the CMS detector, corresponding to an integrated ...luminosity of 35.9 fb$^{−1}$. The inclusive cross section is measured to be σ$_{tot}$(pp → WZ) = 48.09$_{− 0.96}^{+ 1.00}$ (stat)$_{− 0.37}^{+ 0.44}$ (theo)$_{− 2.17}^{+ 2.39}$ (syst) ± 1.39(lum) pb, resulting in a total uncertainty of −2.78/+2.98 pb. Fiducial cross section and ratios of charge-dependent cross section measurements are provided. Differential cross section measurements are also presented with respect to three variables: the Z boson transverse momentum p$_{T}$, the leading jet p$_{T}$, and the M(WZ) variable, defined as the invariant mass of the system composed of the three leptons and the missing transverse momentum. Differential measurements with respect to the W boson p$_{T}$, separated by charge, are also shown. Results are consistent with standard model predictions, favouring next-to-next-to-leading-order predictions over those at next-to-leading order. Constraints on anomalous triple gauge couplings are derived via a binned maximum likelihood fit to the M(WZ) variable.
Measurements of differential cross sections for inclusive very forward jet production in proton-lead collisions as a function of jet energy are presented. The data were collected with the CMS ...experiment at the LHC in the laboratory pseudorapidity range −6.6 < η < −5.2. Asymmetric beam energies of 4 TeV for protons and 1.58 TeV per nucleon for Pb nuclei were used, corresponding to a center-of-mass energy per nucleon pair of $ \sqrt{s_{\mathrm{NN}}} $ = 5.02 TeV. Collisions with either the proton (p+Pb) or the ion (Pb+p) traveling towards the negative η hemisphere are studied. The jet cross sections are unfolded to stable-particle level cross sections with p$_{T}$ ≳ 3 GeV, and compared to predictions from various Monte Carlo event generators. In addition, the cross section ratio of p+Pb and Pb+p data is presented. The results are discussed in terms of the saturation of gluon densities at low fractional parton momenta. None of the models under consideration describes all the data over the full jet-energy range and for all beam configurations. Discrepancies between the differential cross sections in data and model predictions of more than two orders of magnitude are observed.
A search for new massive particles decaying into a pair of Higgs bosons in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. Data were collected with the CMS detector at the ...LHC, corresponding to an integrated luminosity of 35.9 fb$^{−}^{1}$. The search is performed for resonances with a mass between 0.8 and 3.5 TeV using events in which one Higgs boson decays into a bottom quark pair and the other decays into two W bosons that subsequently decay into a lepton, a neutrino, and a quark pair. The Higgs boson decays are reconstructed with techniques that identify final state quarks as substructure within boosted jets. The data are consistent with standard model expectations. Exclusion limits are placed on the product of the cross section and branching fraction for generic spin-0 and spin-2 massive resonances. The results are interpreted in the context of radion and bulk graviton production in models with a warped extra spatial dimension. These are the best results to date from searches for an HH resonance decaying to this final state, and they are comparable to the results from searches in other channels for resonances with masses below 1.5 TeV.
A search for the production of a pair of top squarks at the LHC is presented. This search targets a region of parameter space where the kinematics of top squark pair production and top quark pair ...production are very similar, because of the mass difference between the top squark and the neutralino being close to the top quark mass. The search is performed with 35.9 fb$^{−1}$ of proton-proton collisions at a centre-of-mass energy of $ \sqrt{s}=13 $ TeV, collected by the CMS detector in 2016, using events containing one electron-muon pair with opposite charge. The search is based on a precise estimate of the top quark pair background, and the use of the M$_{T2}$ variable, which combines the transverse mass of each lepton and the missing transverse momentum. No excess of events is found over the standard model predictions. Exclusion limits are placed at 95% confidence level on the production of top squarks up to masses of 208 GeV for models with a mass difference between the top squark and the lightest neutralino close to that of the top quark.
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.
Search results are presented for physics beyond the standard model in final states with two opposite-charge, same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to ...an integrated luminosity of 35.9 fb$^{−1}$ of proton-proton collisions at $ \sqrt{s}=13 $ TeV collected with the CMS detector at the LHC in 2016. The analysis uses the invariant mass of the lepton pair, searching for a kinematic edge or a resonant-like excess compatible with the Z boson mass. The search for a kinematic edge targets production of particles sensitive to the strong force, while the resonance search targets both strongly and electroweakly produced new physics. The observed yields are consistent with the expectations from the standard model, and the results are interpreted in the context of simplified models of supersymmetry. In a gauge mediated supersymmetry breaking (GMSB) model of gluino pair production with decay chains including Z bosons, gluino masses up to 1500–1770 GeV are excluded at the 95% confidence level depending on the lightest neutralino mass. In a model of electroweak chargino-neutralino production, chargino masses as high as 610 GeV are excluded when the lightest neutralino is massless. In GMSB models of electroweak neutralino-neutralino production, neutralino masses up to 500-650 GeV are excluded depending on the decay mode assumed. Finally, in a model with bottom squark pair production and decay chains resulting in a kinematic edge in the dilepton invariant mass distribution, bottom squark masses up to 980–1200 GeV are excluded depending on the mass of the next-to-lightest neutralino.
Searches for resonant and nonresonant pair-produced Higgs bosons (HH) decaying respectively into ℓνℓν, through either W or Z bosons, and $ \mathrm{b}\overline{\mathrm{b}} $ are presented. The ...analyses are based on a sample of proton-proton collisions at $ \sqrt{s}=13 $ TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. Data and predictions from the standard model are in agreement within uncertainties. For the standard model HH hypothesis, the data exclude at 95% confidence level a product of the production cross section and branching fraction larger than 72 fb, corresponding to 79 times the standard model prediction. Constraints are placed on different scenarios considering anomalous couplings, which could affect the rate and kinematics of HH production. Upper limits at 95% confidence level are set on the production cross section of narrow-width spin-0 and spin-2 particles decaying to Higgs boson pairs, the latter produced with minimal gravity-like coupling.
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