Yazar "Benato, L." seçeneğine göre listele

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    Measurements of polarization and spin correlation and observation of entanglement in top quark pairs using lepton plus jets events from proton-proton collisions at √s=13 TeV
    (Amer Physical Soc, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.; Chatterjee, S.; Özdemir, Kadirhan
    Measurements of the polarization and spin correlation in top quark pairs (t (t) over bar) are presented using events with a single electron or muon and jets in the final state. The measurements are based on proton-proton collision data from the LHC at root s = 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb(-1). All coefficients of the polarization vectors and the spin correlation matrix are extracted simultaneously by performing a binned likelihood fit to the data. The measurement is performed inclusively and in bins of additional observables, such as the mass of the t (t) over bar system and the top quark scattering angle in the t (t) over bar rest frame. The measured polarization and spin correlation are in agreement with the standard model. From the measured spin correlation, conclusions on the t (t) over bar spin entanglement are drawn by applying the Peres-Horodecki criterion. The standard model predicts entangled spins for t (t) over bart states at the production threshold and at high masses of the t (t) over bart system. Entanglement is observed for the first time in events at high t (t) over bar mass, where a large fraction of the t (t) over bar decays are spacelike separated, with an expected and observed significance of above 5 standard deviations.
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    Performance of the CMS high-level trigger during LHC Run 2
    (Iop Publishing Ltd, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.; Chatterjee, S.; Özdemir, Kadirhan
    The CERN LHC provided proton and heavy ion collisions during its Run 2 operation period from 2015 to 2018. Proton-proton collisions reached a peak instantaneous luminosity of 2.1 x 10(34) cm(-2)s(-1), twice the initial design value, at root s = 13 TeV. The CMS experiment records a subset of the collisions for further processing as part of its online selection of data for physics analyses, using a two-level trigger system: the Level-1 trigger, implemented in custom-designed electronics, and the high-level trigger, a streamlined version of the offline reconstruction software running on a large computer farm. This paper presents the performance of the CMS high-level trigger system during LHC Run 2 for physics objects, such as leptons, jets, and missing transverse momentum, which meet the broad needs of the CMS physics program and the challenge of the evolving LHC and detector conditions. Sophisticated algorithms that were originally used in offline reconstruction were deployed online. Highlights include a machine-learning b tagging algorithm and a reconstruction algorithm for tau leptons that decay hadronically.
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    Search for the Z Boson Decay to ττμμ in Proton-Proton Collisions at √s=13 TeV
    (Amer Physical Soc, 2024) Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Benato, L.; Bergauer, T.; Chatterjee, S.
    The first search for the Z boson decay to tau tau mu mu at the CERN LHC is presented, based on data collected by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb(-1). The data are compatible with the predicted background. For the first time, an upper limit at the 95% confidence level of 6.9 times the standard model expectation is placed on the ratio of the Z -> tau tau mu mu to Z -> 4 mu branching fractions. Limits are also placed on the six flavor-conserving four-lepton effective-field-theory operators involving two muons and two tau leptons, for the first time testing all such operators.