Observation of $B_{(s)}^0\to J/\ddot{I}ˆp\overline{p}$ decays and precision measurements of the $B_{(s)}^0$ masses

Abstract

The first observation of the decays $B_{(s)}^0\to J/\ddot{I}ˆp\overline{p}$ is reported, using proton-proton collision data corresponding to an integrated luminosity of $5.2{\text{fb}}^{-1}$, collected with the \mbox{LHCb}\xspace detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are \begin{align*} \mathcal{B}(B^0 \to J/ψp \overline{p}) &= (4.51\pm 0.40\; \text{(stat)} \pm 0.44\; \text{(syst)}) \times 10^{-7}, \\ \mathcal{B}(B^0_s \to J/ψp \overline{p}) &= (3.58\pm 0.19\; \text{(stat)} \pm 0.39\; \text{(syst)}) \times 10^{-6}. \end{align*} For the $B_s^0$ meson, the result is much higher than the expected value of $\mathcal{O}(10^{-9})$. The small available phase space in these decays also allows for the most precise single measurement of both the $B^0$ mass as $5279.74\pm 0.30(\mathrm{stat})\pm 0.10(\mathrm{syst})$ MeV, and the $B_s^0$ mass as $5366.85\pm 0.19(\mathrm{stat})\pm 0.13(\mathrm{syst})$ MeV.

All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-046.html