Study of Bc+→J/ψDs+ and Bc+→J/ψDs∗+ decays in pp collisions at √s = 13 TeV with the ATLAS detector

A study of B_c^+ → J/ψD_s^+ and B_c^+ → J/ψD_s^{+} decays using 139 fb^{-1} of integrated luminosity collected with the ATLAS detector from √s = 13 TeV pp collisions at the LHC is presented. The ratios of the branching fractions of the two decays to the branching fraction of the B_c^+ → J/ψπ^+ decay are measured: B(B_c^+ → J/ψD_s^+)/B(B_c^+ → J/ψπ^+) = 2.76 ± 0.47 and B(B_c^+ → J/ψD_s^{+})/B(B_c^+ → J/ψπ^+) = 5.33 ± 0.96. The ratio of the branching fractions of the two decays is found to be B(B_c^+ → J/ψD_s^{+})/B(B_c^+ → J/ψD_s^+) = 1.93 ± 0.26. For the B_c^+ → J/ψD_s^{+} decay, the transverse polarization fraction, Γ_{++}/Γ, is measured to be 0.70 ± 0.11. The reported uncertainties include both the statistical and systematic components added in quadrature. The precision of the measurements exceeds that in all previous studies of these decays. These results supersede those obtained in the earlier ATLAS study of the same decays with √s = 7 and 8 TeV pp collision data. A comparison with available theoretical predictions for the measured quantities is presented.