# Observation of ${B}_{\left(s\right)}^{0}\to J/\psi p\overline{p}$ Decays and Precision Measurements of the ${B}_{\left(s\right)}^{0}$ Masses

28 May 2019

Abstract: The first observation of the decays ${B}_{\left(s\right)}^{0}\to J/\psi p\overline{p}$ is reported, using proton-proton collision data corresponding to an integrated luminosity of $5.2\text{}\text{}{\mathrm{fb}}^{-1}$, collected with the LHCb 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 $B\left({B}^{0}\to J/\psi p\overline{p}\right)=\left[4.51±0.40\left(\text{stat}\right)±\phantom{\rule{0ex}{0ex}}0.44\left(\text{syst}\right)\right]×{10}^{-7}$, $B\left({B}_{s}^{0}\to J/\psi p\overline{p}\right)=\left[3.58±0.19\left(\text{stat}\right)±0.39\left(\text{syst}\right)\right]×{10}^{-6}$. For the ${B}_{s}^{0}$ meson, the result is much higher than the expected value of $O\left({10}^{-9}\right)$. The small available phase space in these decays also allows for the most precise single measurement of both the ${B}^{0}$ mass as $5279.74±0.30\left(\text{stat}\right)±0.10\left(\text{syst}\right)\text{}\text{}\mathrm{MeV}$ and the ${B}_{s}^{0}$ mass as $5366.85±0.19\left(\text{stat}\right)±0.13\left(\text{syst}\right)\text{}\text{}\mathrm{MeV}$.

Published in: Physical Review Letters 122 (2019)