Study of Bs0 → J/ψπ ⁺π ⁻K ⁺K ⁻ decays

The decays Bs0 → 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 Bs0 → J / ψK ∗ 0K ¯ ∗ 0 and Bs0 → χ c1(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 χ c1(3872)ϕ, J / ψK ∗ 0K ¯ ∗ 0, ψ(2S)ϕ and χ c1(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±6MeV/c2,ΓX(4740)=53±15±11MeV, where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the Bs0 meson is performed and gives a value of mBs0=5366.98±0.07±0.13MeV/c2. [Figure not available: see fulltext.]