1,450 research outputs found

    Measurement of the B s 0 → J / ψK S 0 effective lifetime from proton-proton collisions at s = 13 TeV

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    Abstract The effective lifetime of the B s 0 meson in the decay B s 0 → J / ψK S 0 is measured using data collected during 2016–2018 with the CMS detector in s = 13 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 140 fb−1. The effective lifetime is determined by performing a two-dimensional unbinned maximum likelihood fit to the B s 0 meson invariant mass and proper decay time distributions. The resulting value of 1.59 ± 0.07(stat) ± 0.03(syst) ps is the most precise measurement to date and is in good agreement with the expected value

    Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery

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    In the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the articl

    Observation of nuclear modifications in W±^{±} boson production in pPb collisions at √S^{S}NN = 8.16 TeV

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    The production of W-+/- bosons is studied in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of root s(NN) = 8.16 TeV. Measurements are performed in the W-+/- -> mu(+/-)nu(mu) channel using a data sample corresponding to an integrated luminosity of 173.4 +/- 6.1 nb(-1), collected by the CMS Collaboration at the LHC. The number of positively and negatively charged W bosons is determined separately in the muon pseudorapidity region in the laboratory frame vertical bar eta(mu)(lab)vertical bar < 2.4 and transverse momentum p(T)(mu) > 25 GeV/c. The W-+/- boson differential cross sections, muon charge asymmetry, and the ratios of W-+/- boson yields for the proton-going over the Pb-going beam directions are reported as a function of the muon pseudorapidity in the nucleon-nucleon centre-of-mass frame. The measurements are compared to the predictions from theoretical calculations based on parton distribution functions (PDFs) at next-to-leading-order. The results favour PDF calculations that include nuclear modifications and provide constraints on the nuclear PDF global fits. (C) 2019 The Author(s). Published by Elsevier B.V

    Search for a heavy composite Majorana neutrino in events with dilepton signatures from proton-proton collisions at √s=13 Tev

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    Results are presented of a search for a heavy Majorana neutrino N ⠃ decaying into two same-flavor leptons ⠃ (electrons or muons) and a quark-pair jet. A model is considered in which the N ⠃ is an excited neutrino in a compositeness scenario. The analysis is performed using a sample of proton-proton collisions at & RADIC;s = 13 TeV recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138 fb-1. The data are found to be in agreement with the standard model prediction. For the process in which the N ⠃ is produced in association with a lepton, followed by the decay of the N ⠃ to a same-flavor lepton and a quark pair, an upper limit at 95% confidence level on the product of the cross section and branching fraction is obtained as a function of the N ⠃ mass mN ⠃ and the compositeness scale ⠄. For this model the data exclude the existence of Ne (N & mu;) for mN ⠃ below 6.0 (6.1) TeV, at the limit where mN ⠃ is equal to ⠄. For mN ⠃ N 1 TeV, values of ⠄ less than 20 (23) TeV are excluded. These results represent a considerable improvement in sensitivity, covering a larger parameter space than previous searches in pp collisions at 13 TeV.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3

    Measurement of the double-differential inclusive jet cross section in proton-proton collisions at s s \sqrt{s} = 5.02 TeV

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    Abstract The inclusive jet cross section is measured as a function of jet transverse momentum p T and rapidity y. The measurement is performed using proton-proton collision data at s s \sqrt{s} = 5.02 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 27.4 pb −1. The jets are reconstructed with the anti-k T algorithm using a distance parameter of R = 0.4, within the rapidity interval |y| < 2, and across the kinematic range 0.06 < p T < 1 TeV. The jet cross section is unfolded from detector to particle level using the determined jet response and resolution. The results are compared to predictions of perturbative quantum chromodynamics, calculated at both next-to-leading order and next-to-next-to-leading order. The predictions are corrected for nonperturbative effects, and presented for a variety of parton distribution functions and choices of the renormalization/factorization scales and the strong coupling α S

    Bottom quark energy loss and hadronization with B+ and B s 0 nuclear modification factors using pp and PbPb collisions at s NN = 5.02 TeV

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    Abstract The production cross sections of B s 0 and B+ mesons are reported in proton-proton (pp) collisions recorded by the CMS experiment at the CERN LHC with a center-of-mass energy of 5.02 TeV. The data sample corresponds to an integrated luminosity of 302 pb−1. The cross sections are based on measurements of the B s 0 → J/ψ(μ+μ−)ϕ(1020)(K+K−) and B+ → J/ψ(μ+μ−)K+ decay channels. Results are presented in the transverse momentum (pT) range 7–50 GeV/c and the rapidity interval |y| 10 GeV/c, both mesons are found to be suppressed in PbPb collisions (with RAA values significantly below unity), with less suppression observed for the B s 0 mesons. In this pT range, the RAA values for the B+ mesons are consistent with those for inclusive charged hadrons and D0 mesons. Below 10 GeV/c, both B+ and B s 0 are found to be less suppressed than either inclusive charged hadrons or D0 mesons, with the B s 0 RAA value consistent with unity. The RAA values found for the B+ and B s 0 are compared to theoretical calculations, providing constraints on the mechanism of bottom quark energy loss and hadronization in the quark-gluon plasma, the hot and dense matter created in ultrarelativistic heavy ion collisions

    Observation of B 0 → ψ (2S)K S 0 π + π - and B s 0 → ψ (2S)K S 0 decays

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    Using a data sample of s√=13TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of 103~fb−1, the B0s→ψ(2S)K0S and B0→ψ(2S)K0Sπ+π− decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to B(B0s→ψ(2S)K0S)/B(B0→ψ(2S)K0S)=(3.33±0.69(stat)±0.11(syst)±0.34(fs/fd))×10−2 and B(B0→ψ(2S)K0Sπ+π−)/B(B0→ψ(2S)K0S)=0.480±0.013(stat)±0.032(syst), where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of B0s and B0 mesons, fs/fd

    CORE 3.2 (COmpendium of RElations, Version 3.2)

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    The present CORE 3.2 (COmpendium of RElations, Version 3.2) contains various formulas and relations used in the practical calculations in the Standard Model. The properties of the Pauli, Dirac, Gell--Mann matrices, wave functions of free fermions and gauge bosons are considered. We present the full Lagrangian of the Standard Model and the corresponding Feynman rules. The method of the evaluation of the Feynman (loop) integrals and calculations in non-covariant gauges is considered. We discuss in brief the relativistic kinematic and present a large number of the matrix elements of the various processes in the Standard Model.Comment: 81 pages, 21 figures, scripts.sty. arXiv admin note: substantial text overlap with arXiv:hep-ph/950745

    Measurement of the τ lepton polarization in Z boson decays in proton-proton collisions at s s \sqrt{s} = 13 TeV

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    Abstract The polarization of τ leptons is measured using leptonic and hadronic τ lepton decays in Z → τ + τ − events in proton-proton collisions at s s \sqrt{s} = 13 TeV recorded by CMS at the CERN LHC with an integrated luminosity of 36.3 fb −1. The measured τ − lepton polarization at the Z boson mass pole is P τ Z Pτ(Z) {\mathcal{P}}_{\tau}\left(\textrm{Z}\right) = −0.144 ± 0.006 (stat) ± 0.014 (syst) = −0.144 ± 0.015, in good agreement with the measurement of the τ lepton asymmetry parameter of A τ = 0.1439 ± 0.0043 = − P τ Z Pτ(Z) -{\mathcal{P}}_{\tau}\left(\textrm{Z}\right) at LEP. The τ lepton polarization depends on the ratio of the vector to axial-vector couplings of the τ leptons in the neutral current expression, and thus on the effective weak mixing angle sin2 θ W eff θWeff {\theta}_{\textrm{W}}^{\textrm{eff}} , independently of the Z boson production mechanism. The obtained value sin2 θ W eff θWeff {\theta}_{\textrm{W}}^{\textrm{eff}} = 0.2319 ± 0.0008(stat) ± 0.0018(syst) = 0.2319 ± 0.0019 is in good agreement with measurements at e + e − colliders

    Azimuthal correlations in Z +jets events in proton–proton collisions at s=13TeV\sqrt{s} = 13\,\text {Te}\hspace{-.08em}\text {V} s = 13 Te V

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    Abstract The production of Z bosons associated with jets is measured in pp\text {p}\text {p} pp collisions at s=13TeV\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} s = 13 Te V with data recorded with the CMS experiment at the LHC corresponding to an integrated luminosity of 36.3 fb1\,\text {fb}^{-1} fb - 1 . The multiplicity of jets with transverse momentum pT>30GeVp_{\textrm{T}} > 30\,\text {Ge}\hspace{-.08em}\text {V} p T > 30 Ge V is measured for different regions of the Z boson’s pT()p_{\textrm{T}} (\text {Z }) p T ( Z ) , from lower than 10 GeV\,\text {Ge}\hspace{-.08em}\text {V} Ge V to higher than 100 GeV\,\text {Ge}\hspace{-.08em}\text {V} Ge V . The azimuthal correlation Δϕ\varDelta \phi Δ ϕ between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions of pT()p_{\textrm{T}} (\text {Z }) p T ( Z ) . The measurements are compared with several predictions at leading and next-to-leading orders, interfaced with parton showers. Predictions based on transverse-momentum dependent parton distributions and corresponding parton showers give a good description of the measurement in the regions where multiple parton interactions and higher jet multiplicities are not important. The effects of multiple parton interactions are shown to be important to correctly describe the measured spectra in the low pT()p_{\textrm{T}} (\text {Z }) p T ( Z ) regions
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