Observation of a peaking structure in the J/psi phi mass spectrum from B(+/-) to J/psi phi K(+/-) decays

Understand

A peaking structure in the J/psi phi mass spectrum near threshold is observed in B(+/-) to J/psi phi K(+/-) decays, produced in pp collisions at sqrt(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/psi, corresponds to an integrated luminosity of 5.2 inverse femtobarns.
• 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 Gamma = 28 +15 -11 (stat.) +- 19 (syst.) MeV, respectively.