Evidence for a Narrow Near-Threshold Structure in the J/ψϕ Mass Spectrum in B+→J/ψϕK+ Decays

Abstract

Evidence is reported for a narrow structure near the J/ψϕ threshold in exclusive B+→J/ψϕK+ decays produced in p̅ p collisions at √s=1.96 TeV. A signal of 14±5 events, with statistical significance in excess of 3.8 standard deviations, is observed in a data sample corresponding to an integrated luminosity of 2.7 fb-1, collected by the CDF II detector. The mass and natural width of the structure are measured to be 4143.0±2.9(stat)±1.2(syst) MeV/c2 and 11.7-5.0+8.3(stat)±3.7(syst) MeV/c2.