Exotic quarkonium states in CMS
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The studies of the production of the X(3872), either prompt or from B-hadron decays, and of the J/ψϕ mass spectrum in B-hadron decays have been carried out by using pp collisions at \(\sqrt s \) = 7 TeV collected with the CMS detector at the LHC. The cross-section ratio of the X(3872) with respect to the ψ(2S) in the J/ψπ + π − decay channel and the fraction of X(3872) coming from B-hadron decays are measured as a function of transverse momentum (p T ), covering unprecedentedly high values of p T . For the first time, the prompt X(3872) cross section times branching fraction is extracted differentially in p T and compared with NRQCD predictions. The dipion invariant-mass spectrum of the J/ψπ + π − system in the X(3872) decay is also investigated. A peaking structure in the J/ψϕ mass spectrum near threshold is observed in B ± → J/ψϕK ± decays. The data sample, selected on the basis of the dimuon decay mode of the J/ψ, corresponds to an integrated luminosity of 5.2 fb−1. Fitting the structure to an S-wave relativistic Breit–Wigner lineshape above a three-body phase-space nonresonant component gives a signal statistical significance exceeding five standard deviations. The fitted mass and width values are m = 4148.0 ± 2.4(stat.) ± 6.3(syst.) MeV and Γ = 28+15 − 11(stat.) ± 19(syst.) MeV, respectively. Evidence for an additional peaking structure at higher J/ψϕ mass is also reported.
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