Observation of ηc(2S) →pp¯ and search for X(3872) →pp¯ decays

Journal article

The first observation of the decay ηc(2S) → pp is reported using proton–proton collision data corresponding to an integrated luminosity of 3.0fb^−1 recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ηc(2S)resonance is produced in the decay B+→[cc¯]K+. The product of branching fractions normalised to that for the J/ψ intermediate state, Rηc(2S), is measured to be Rηc (2S) ≡ B(B+→ηc(2S)K+)×B(ηc(2S)→ p¯p )/B(B+→ J/ψ K+)×B( J/ψ → p¯p ) = (1.58±0.33±0.09)×10^−2, where the first uncertainty is statistical and the second systematic. No signals for the decays B+→X(3872)(→pp¯)K+and B+→ψ(3770)(→pp¯p)K+are seen, and the 95% confidence level upper limits on their relative branching ratios are found to be RX(3872)<0.25 ×10−2and Rψ(3770)<0.10. In addition, the mass differences between the ηc(1S)and the J/ψstates, between the ηc(2S)and the ψ(2S)states, and the natural width of the ηc(1S)are measured as M J/ψ − Mηc (1S) = 110.2±0.5 ±0.9MeV, Mψ(2S) − Mηc (2S) = 52.5±1.7±0.6MeV, Γηc (1S) = 34.0±1.9±1.3MeV.

Authors: Aaij, R; Adeva, B; Adinolfi, M; Evans, T; Gandini, P

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Physics Letters B
• Volume: 769
• Pages: 305-313
• Publication date: 2017-03-01
• Acceptance date: 2017-03-23
• DOI: 10.1016/j.physletb.2017.03.046
• ISSN: 0370-2693
• Keywords: hep-ex