Semileptonic decays of charmed and beauty baryons with heavy sterile neutrinos in the final state

Abstract

We obtain tree-level estimates of various differential branching ratios of heavy baryon decays with massive sterile neutrinos ${\ensuremath{\nu}}_{x}$ in the final state. Generally, charmed baryons are found to be less promising than charmed mesons, in contrast to $b$ hadrons. In the latter case, branching ratios of beauty mesons and baryons into sterile neutrinos are of the same order. As a consequence, at high energies beauty baryons give contribution to sterile neutrino production comparable to the contribution of beauty mesons (up to about 15%). Experimental limits on active-to-sterile mixing are quite strong for neutrinos lighter than $D$ mesons but for heavier neutrinos they are weaker. As an example, for neutrino masses in the range $2\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}{m}_{{\ensuremath{\nu}}_{x}}\ensuremath{\lesssim}2.5\text{ }\text{ }\mathrm{GeV}$, current data imply that the bounds on ${\ensuremath{\Lambda}}_{b}$-hyperon branching ratios into sterile neutrinos are $\mathrm{Br}({\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}+{e}^{\ensuremath{-}}+{\ensuremath{\nu}}_{x})\ensuremath{\lesssim}1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}--1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathrm{Br}({\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}+{\ensuremath{\mu}}^{\ensuremath{-}}+{\ensuremath{\nu}}_{x})\ensuremath{\lesssim}3.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}--1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$.