Observation of a peaking structure in the J/psi phi mass spectrum from B-+/- -> J/psi phi K-+/- decays
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.