Study of $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ → J/ψπ+π−K+K− decays

The decays $ {\mathrm{B}}_{\mathrm{s}}^0 $ → 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 $ {\mathrm{B}}_{\mathrm{s}}^0 $ → $ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $ and $ {\mathrm{B}}_{\mathrm{s}}^0 $ → 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, $ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 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$ {\displaystyle \begin{array}{c}{m}_{\mathrm{X}(4740)}=4741\pm 6\pm 6\kern0.5em \mathrm{MeV}/{c}^2,\\ {}{\Gamma}_{\mathrm{X}(4740)}=53\pm 15\pm 11\kern0.5em \mathrm{MeV},\end{array}} $where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the $ {\mathrm{B}}_{\mathrm{s}}^0 $ meson is performed and gives a value of$ {m}_{{\mathrm{B}}_{\mathrm{s}}^0}=5366.98\pm 0.07\pm 0.13\kern0.5em \mathrm{MeV}/{c}^2. $[graphic not available: see fulltext]