Observation of a peaking structure in the J / ψ ϕ mass spectrum from B ± → J / ψ ϕ K ± decays

Abstract

A peaking structure in the J/ψφ mass spectrum near threshold is observed in B ±→J/ψφK± decays, produced in pp collisions at √s=7 TeV collected with the CMS detector at the LHC. 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. © 2014 The Authors.