Observation of the $B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^0$ decay

Abstract

The first observation of the $B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^0$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9fb${}^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the $B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{€}^{+}$ channel is measured to be $$\frac{\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{€}^{+}\ddot{I}{€}^0)}{\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{€}^{+})}=2.80\pm 0.15\pm 0.11\pm 0.16,$$ where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for $B^{+}\to J/\ddot{I}ˆK^{\ast +}$ and $B^{+}\to J/\ddot{I}ˆK^{+}$ decays, which are used to determine the $\ddot{I}{€}^0$ detection efficiency. The $\ddot{I}{€}^{+}\ddot{I}{€}^0$ mass spectrum is found to be consistent with the dominance of an intermediate $\ddot{I}{}^{+}$ contribution in accordance with a model based on QCD factorisation.

30 pages, 6 figures. All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-046.html (LHCb public pages)