124 research outputs found

    Search for dijet resonances using events with three jets in proton-proton collisions at root s=13 TeV

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    A search for a narrow resonance with a mass between 350 and 700 GeV, and decaying into a pair of jets, is performed using proton-proton collision events containing at least three jets. The data sample corresponds to an integrated luminosity of 18.3 fb(-1) recorded at root s = 13 TeV with the CMS detector. Data are collected with a technique known as "data scouting", in which the events are reconstructed, selected, and recorded at a high rate in a compact form by the high-level trigger. The three-jet final state provides sensitivity to lower resonance masses than in previous searches using the data scouting technique. The spectrum of the dijet invariant mass, calculated from the two jets with the largest transverse momenta in the event, is used to search for a resonance. No significant excess over a smoothly falling background is found. Limits at 95% confidence level are set on the production cross section of a narrow dijet resonance and compared with the cross section of a vector dark matter mediator coupling to dark matter particles and quarks. Translating to a model where the narrow resonance interacts only with quarks, upper limits on this coupling range between 0.10 and 0.15, depending on the resonance mass. These results represent the most stringent upper limits in the mass range between 350 and 450 GeV obtained with a flavor-inclusive dijet resonance search. (C) 2020 The Author(s). Published by Elsevier B.V.Peer reviewe

    Determination of the strong coupling constant α_S(m_Z) from measurements of inclusive W± and Z boson production cross sections in proton-proton collisions at √s = 7 and 8 TeV

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    Twelve measurements of inclusive cross sections of W± and Z boson production, performed in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, are compared with perturbative quantum chromodynamics calculations at next-to-next- to-leading order (NNLO) accuracy obtained with the CT₁₄, HERAPDF2.0, MMHT₁₄, and NNPDF_(3.0) parton distribution functions (PDFs). Data and theory agree well for all PDF sets, taking into account the experimental and theoretical uncertainties. A novel procedure is employed to extract the strong coupling constant at the Z pole mass from a detailed comparison of all the experimental fiducial cross sections to the corresponding NNLO theoretical predictions, yielding α_S(m_Z) = 0.1163^(+0.0024)_(−0.0031) (CT₁₄), 0.1072^(+0.0043)_(−0.0040) (HERAPDF_(2.0)), 0.1186 ± 0.0025 (MMHT₁₄), and 0.1147 ± 0.0023 (NNPDF_(3.0)). Using the results obtained with the CT₁₄ and MMHT₁₄ PDFs, which yield the most robust and stable α_S(m_Z) extractions, a value α_S(m_Z) = 0.1175^(+0.0025)_(−0.0028) is determined

    Study of the B +→ J / ψ Λ ¯ p decay in proton-proton collisions at √s = 8 TeV

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    A study of the B⁺→J/ψΛ̅p decay using proton-proton collision data collected at √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 B(B⁺→J/ψΛ̅p)/B(B+→J/ψK*(892)⁺) is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011(B))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of Λ̅ and K*(892)⁺ decays to reconstructed final states. The invariant mass distributions of the J/ψΛ̅, J/ψp, and Λ̅p systems produced in the B+→J/ψΛ̅p 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 Λ̅p system

    A multi-dimensional search for new heavy resonances decaying to boosted WW, WZ, or ZZ boson pairs in the dijet final state at 13TeV

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    A search in an all-jet final state for new massive resonances decaying to WW, WZ, or ZZ boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an integrated luminosity of 77.3 fb(-1) recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13TeV. The search is focussed on potential narrow-width resonances with masses above 1.2TeV, where the decay products of each W or Z boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector triplet model, spin-1 Z' and W' resonances with masses below 3.5 and 3.8TeV, respectively, are excluded at 95% confidence level. In a bulk graviton model, upper limits on cross sections are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2TeV, respectively. The limits presented in this paper are the best to date in the dijet final state.Peer reviewe

    A multi-dimensional search for new heavy resonances decaying to boosted  W \text{ W }{}{}  W \text{ W }{}{} ,  W \text{ W }{}{}  Z \text{ Z }{}{} , or  Z \text{ Z }{}{}  Z \text{ Z }{}{} boson pairs in the dijet final state at 13 TeV

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    A search in an all-jet final state for new massive resonances decaying to WW, WZ, or ZZ boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an integrated luminosity of 77.3 fb1^{-1} recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13TeV. The search is focussed on potential narrow-width resonances with masses above 1.2TeV, where the decay products of each W or Z boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector tripletmodel, spin-1Z` and W` resonances with masses below 3.5 and 3.8 TeV, respectively, are excluded at 95% confidence level. In a bulk graviton model, upper limits on cross sections are set between 27 and 0.2 fb for resonance masses between 1.2 and 5.2TeV, respectively. The limits presented in this paper are the best to date in the dijet final state

    Study of the B⁺ → J/ψΛp decay in proton-proton collisions at √s = 8 TeV

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    A study of the B⁺ → J/ψΛp decay using proton-proton collision data collected at √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 B(B⁺ → J/ψΛp)/B(B⁺ → J/ψK∗(892)⁺) is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011(B))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of Λ and K*(892)⁺ decays to reconstructed final states. The invariant mass distributions of the J/ψΛ, J/ψp, and Λp systems produced in the B⁺ → J/ψΛp 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 Λp system

    Search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at s \sqrt{\mathrm{s}} = 13 TeV

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    Results are reported from a search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at s \sqrt{\mathrm{s}} = 13 TeV. The data sample corresponds to an integrated luminosity of 33.2 fb1^{-1} recorded by the CMS experiment at the LHC in 2016. The search exploits τ leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction B(τ → 3μ) of 8.0 x 108^{-8} at 90% confidence level is obtained, with an expected upper limit of 6.9 x 108^{-8}

    Measurement of the top quark Yukawa coupling from tt̄ kinematic distributions in the dilepton final state in proton-proton collisions at √s = 13  TeV

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    A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at √s = 13  TeV, corresponding to an integrated luminosity of 137  fb⁻¹, recorded with the CMS detector. The coupling strength with respect to the standard model value, Y_t, is determined from kinematic distributions in tt̄ final states containing ee, μμ, or eμ pairs. Variations of the Yukawa coupling strength lead to modified distributions for tt̄ production. In particular, the distributions of the mass of the tt̄ system and the rapidity difference of the top quark and antiquark are sensitive to the value of Y_t. The measurement yields a best fit value of Y_t = 1.16^(+0.24)_(−0.35), bounding Y_t < 1.54 at a 95% confidence level
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