Study of B0 s → J/ψπ+π −K+K− decays

Abstract

The decays B 0 s → J/ψπ+π −K+K− are studied using a data set corresponding to an integrated luminosity of 9 fb−1 , collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays B 0 s → J/ψK∗0K∗0 and B 0 s → χc1(3872)K+K−, where the K+K− pair does not originate from a φ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χc1(3872)φ, J/ψK∗0K∗0 , ψ(2S)φ and χc1(3872)K+K− states are reported. A structure, denoted as X(4740), is observed in the J/ψφ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be mX(4740) = 4741 ± 6 ± 6 MeV/c2 , ΓX(4740) = 53 ± 15 ± 11 MeV , where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the B 0 s meson is performed and gives a value of mB0 s = 5366.98 ± 0.07 ± 0.13 MeV/c2 .