Search for the rare hadronic decay $B_s^0\to p\overline{p}$

A search for the rare hadronic decay $B_s^0\to p\overline{p}$ is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$. No evidence of the decay is found and an upper limit on its branching fraction is set at $\mathcal{B}(B_s^0\to p\overline{p})<4.4(5.1)\times {10}^{-9}$ at 90% (95%) confidence level; this is currently the world’s best upper limit. The decay mode $B^0\to p\overline{p}$ is measured with very large significance, confirming the first observation by the LHCb experiment in 2017. The branching fraction is determined to be $\mathcal{B}(B^0\to p\overline{p})=(1.27\pm 0.15\pm 0.05\pm 0.04)\times {10}^{-8}$, where the first uncertainty is statistical, the second is systematic and the third is due to the external branching fraction of the normalization channel $B^0\to K^{+}{\pi }^{-}$. The combination of the two LHCb measurements of the $B^0\to p\overline{p}$ branching fraction yields $\mathcal{B}(B^0\to p\overline{p})=(1.27\pm 0.13\pm 0.05\pm 0.03)\times {10}^{-8}$.

Figure 1

Invariant-mass distribution of $B^0\to K^{+}{\pi }^{-}$ candidates. The fit result is shown together with each fit model component.

Figure 2

Invariant-mass distribution of $p\overline{p}$ candidates with each fit model component.

Figure 3

Negative logarithm of the profile likelihoods ($-2\mathrm{\Delta }\ln L$) and the corresponding likelihood as a function of the $B_s^0\to p\overline{p}$ branching fraction. The solid blue line represents the statistical-only profile, whereas the dashed red line includes the systematic uncertainties. The solid magenta line shows the distribution of likelihood. The dashed violet vertical line at 0 shows the start point of the integral. The black (cyan) arrow shows the upper limits at 90% (95%) confidence level.