Observation of the charmless purely baryonic decay $\hat{I}{›}_b^0\to \hat{I}›p\overline{p}$

Abstract

A search for the charmless purely baryonic decay $\hat{I}{›}_b^0\to \hat{I}›p\overline{p}$ is performed using proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=13\text{TeV}$ and corresponding to an integrated luminosity of $6.0{\text{fb}}^{-1}$. The signal decay is observed with a significance of 5.1 standard deviations. Its branching fraction is measured for the first time, relative to that of the topologically similar decay $\hat{I}{›}_b^0\to \hat{I}›K^{+}{K}^{-}$. Contributions from intermediate charmonium resonances decaying to the $p\overline{p}$ and $K^{+}{K}^{-}$ final states are explicitly excluded with a requirement on the invariant mass of the companion hadron system, $m(h\bar{h})<2.85\text{GeV}$, where $h$ stands for a proton or a charged kaon. The relative branching fraction is found to be $$\frac{B(\hat{I}{›}_b^0\to \hat{I}›p\overline{p})}{B(\hat{I}{›}_b^0\to \hat{I}›K^{+}{K}^{-})}=(5.1\pm 1.3_{\text{(stat)}}\pm 0.3_{\text{(syst)}})\times 10^{-2}.$$

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1600/ (LHCb public pages)