Exotic quarkonium states in CMS

¹ Universitá degli Studi di Bari
² INFN - Sezione di Bari

^a e-mail: leonardo.cristella@cern.ch

Published online: 22 March 2017

Abstract

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 √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 production cross section for the X(3872) times the unknown branching fraction for the decay of X(3872) →J/ψπ⁺π⁻ is extracted differentially in p_T and compared to theoretical predictions based on the Non-Relativistic QCD (NRQCD) factorization approach. 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 = 28₋₁₁⁺¹⁵ (stat.) ± 19(syst.) MeV, respectively. Evidence for an additional peaking structure at higher J/ψϕ mass is also reported.

The search for resonance-like structures in the B_s⁰π^± invariant mass spectrum do not show any unexpected result. An upper limit on the relative production of the claimed X(5568) and B_s multiplied by the unknown branching fraction of the decay X(5568) → B_sπ^± is estimated to be 3.9% at 95% CL in the most conservative case.