272 research outputs found

    t, 3He and 4He production in Pb-Pb collisions at ‚ąösNN = 5.02 TeV

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    This paper reports the results obtained during the 2019 CERN Summer Student Program. It focuses on production of anti-triton, 3He and 4He in PbPb collisions at ‚ąösNN = 5.02 TeV. The study of the nuclei and anti-nuclei production at the LHC represents a fundamental step in understanding the nucleosynthesis mechanisms in heavy-ion collisions

    Search for a third-generation leptoquark coupled to a ŌĄ \tau lepton and a b quark through single, pair, and nonresonant production in proton-proton collisions at s= \sqrt{s}= 13 TeV

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    A search is presented for a third-generation leptoquark (LQ) coupled exclusively to a ŌĄ \tau lepton and a b quark. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector, corresponding to an integrated luminosity of 138 fb‚ąí1 ^{-1} . Events with ŌĄ \tau leptons and a varying number of jets originating from b quarks are considered, targeting the single and pair production of LQs, as well as nonresonant t t -channel LQ exchange. An excess is observed in the data with respect to the background expectation in the combined analysis of all search regions. For a benchmark LQ mass of 2 TeV and an LQ-b-ŌĄ\tau coupling strength of 2.5, the excess reaches a local significance of up to 2.8 standard deviations. Upper limits at the 95% confidence level are placed on the LQ production cross section in the LQ mass range 0.5-2.3 TeV, and up to 3 TeV for t t -channel LQ exchange. Leptoquarks are excluded below masses of 1.22-1.88 TeV for different LQ models and varying coupling strengths up to 2.5. The study of nonresonant ŌĄŌĄ \tau\tau production through t t -channel LQ exchange allows lower limits on the LQ mass of up to 2.3 TeV to be obtained.A search is presented for a third-generation leptoquark (LQ) coupled exclusively to a ŌĄ\tau lepton and a b quark. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector, corresponding to an integrated luminosity of 138 fb‚ąí1^{-1}. Events with ŌĄ\tau leptons and a varying number of jets originating from b quarks are considered, targeting the single and pair production of LQs, as well as nonresonant tt-channel LQ exchange. An excess is observed in the data with respect to the background expectation in the combined analysis of all search regions. For a benchmark LQ mass of 2 TeV and an LQ-b-ŌĄ\tau coupling strength of 2.5, the excess reaches a local significance of up to 2.8 standard deviations. Upper limits at the 95% confidence level are placed on the LQ production cross section in the LQ mass range 0.5-2.3 TeV, and up to 3 TeV for tt-channel LQ exchange. Leptoquarks are excluded below masses of 1.22-1.88 TeV for different LQ models and varying coupling strengths up to 2.5. The study of nonresonant ŌĄŌĄ\tau\tau production through tt-channel LQ exchange allows lower limits on the LQ mass of up to 2.3 TeV to be obtained

    Development of the CMS detector for the CERN LHC Run 3