Observation of a peaking structure in the J/ψϕ mass spectrum from B±→ J/ψϕK± 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 +15-11 (stat.)±19 (syst.) MeV, respectively. Evidence for an additional peaking structure at higher J/ψϕ mass is also reported.