2,188 research outputs found

    Search for new physics in the multijet and missing transverse momentum final state in proton-proton collisions at √s=8 Tev

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    Measurement of Higgs boson production and properties in the WW decay channel with leptonic final states

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    Study of double parton scattering using W+2-jet events in proton-proton collisions at √s=7 TeV

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    Search for Dark Matter and Supersymmetry with a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton-Proton Collisions at root s=8 TeV

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    Measurements of the tt¯ charge asymmetry using the dilepton decay channel in pp collisions at √s=7 TeV

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    Search for the lepton flavour violating decay B + → K + μ − τ + using B s 2 ∗ 0 decays

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    Abstract: A search is presented for the lepton flavour violating decay B+ → K+μ−τ+ using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1. The τ leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the τ lepton is determined by using B+ mesons from Bs2∗0→B+K− decays. No significant excess is observed, and an upper limit is set on the branching fraction ℬ(B+ → K+μ−τ+) < 3.9 × 10−5 at 90 % confidence level. The obtained limit is comparable to the world-best limit

    First Observation of a Doubly Charged Tetraquark and Its Neutral Partner

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    A combined amplitude analysis is performed for the decays B0→D ̄D0s+π- and B+→D-Ds+π+, which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb-1. Two new resonant states with masses of 2.908±0.011±0.020 GeV and widths of 0.136±0.023±0.013 GeV are observed, which decay to Ds+π+ and Ds+π- respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content [cs ̄ud ̄], and the latter state is a neutral tetraquark composed of [cs ̄ūd] quarks. Both states are found to have spin-parity of 0+, and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet

    Measurement of prompt D+D^+ and Ds+D^+_{s} production in pPbp\mathrm{Pb} collisions at sNN=5.02\sqrt {s_{\mathrm{NN}}}=5.02\,TeV

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    The production of prompt D+D^+ and Ds+D^+_{s} mesons is studied in proton-lead collisions at a centre-of-mass energy of sNN=5.02\sqrt {s_{\mathrm{NN}}}=5.02\,TeV. The data sample corresponding to an integrated luminosity of (1.58±0.02)nb1(1.58\pm0.02)\mathrm{nb}^{-1} is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using D+D^+ and Ds+D^+_{s} candidates with transverse momentum in the range of 0<pT<14GeV/c0<p_{\mathrm{T}} <14\,\mathrm{GeV}/c and rapidities in the ranges of 1.5<y<4.01.5<y^*<4.0 and 5.0<y<2.5-5.0<y^*<-2.5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between D+D^+, Ds+D^+_{s} and D0D^0 mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-006.html (LHCb public pages

    Observation of strangeness enhancement with charmed mesons in high-multiplicity pPbp\mathrm{Pb} collisions at sNN=8.16\sqrt {s_{\mathrm{NN}}}=8.16\,TeV

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    The production of prompt Ds+D^+_{s} and D+D^+ mesons is measured by the LHCb experiment in proton-lead (pPbp\mathrm{Pb}) collisions in both the forward (1.5<y<4.01.5<y^*<4.0) and backward (5.0<y<2.5-5.0<y^*<-2.5) rapidity regions at a nucleon-nucleon center-of-mass energy of sNN=8.16\sqrt {s_{\mathrm{NN}}}=8.16\,TeV. The nuclear modification factors of both Ds+D^+_{s} and D+D^+ mesons are determined as a function of transverse momentum, pTp_{\mathrm{T}}, and rapidity. In addition, the Ds+D^+_{s} to D+D^+ cross-section ratio is measured as a function of the charged particle multiplicity in the event. An enhanced Ds+D^+_{s} to D+D^+ production in high-multiplicity events is observed for the whole measured pTp_{\mathrm{T}} range, in particular at low pTp_{\mathrm{T}} and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity pPbp\mathrm{Pb} collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-021.html (LHCb public pages

    Measurement of χc1(3872) production in proton-proton collisions at \sqrt{s} = 8 and 13 TeV

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