Though not considered in general, purely baryonic decays could shed light on the puzzle of the baryon number asymmetry in the universe by means of a better understanding of the baryonic nature of our matter world. As such, they constitute a yet unexplored class of decay processes worth investigating. We propose to search for purely baryonic decay processes at the LHCb experiment. No such type of decay has ever been observed. In particular, we concentrate on the decay ${\mathrm{\Lambda }}_b^0\to p\overline{p}n$, which is the simplest purely baryonic decay mode, with solely spin-$1/2$ baryons involved. We predict its decay branching ratio to be $\mathcal{B}({\mathrm{\Lambda }}_b^0\to p\overline{p}n)=(2.0_{-0.2}^{+0.3})\times {10}^{-6}$, which is sufficiently large to make the decay mode accessible to LHCb. Our study can be extended to other purely baryonic decays such as ${\mathrm{\Lambda }}_b^0\to p\overline{p}\mathrm{\Lambda }$, ${\mathrm{\Lambda }}_b^0\to \mathrm{\Lambda }\overline{p}\mathrm{\Lambda }$, and ${\mathrm{\Lambda }}_b^0\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}\mathrm{\Lambda }$, as well as to similar decays of antitriplet $b$ baryons such as ${\mathrm{\Xi }}_b^{0,-}$.

• Received 5 April 2016

DOI:https://doi.org/10.1103/PhysRevD.94.014027