Semileptonic decays of charmed and beauty baryons with 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 $\nu_{x}$ in the final state. Heavy sterile neutrinos can be searched for in heavy baryon decays with missing mass as a signature as well as in fixed target experiments, where heavy baryon decays contribute to sterile neutrino production, with sterile neutrino decays as a signature. 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-meson but for heavier neutrinos they are weaker. As an example, for neutrino masses in the range 2 GeV $\lesssim m_{\nu_{x}}\lesssim 2.5$ GeV, current data imply that the bounds on $\Lambda_{b}$-hyperon branching ratios into sterile neutrinos are ${\rm Br}(\Lambda_b\to\Lambda_c+e^-+\nu_x)\lesssim 1.3\cdot10^{-5}-1.7\cdot10^{-6}$ and ${\rm Br}(\Lambda_b\to\Lambda_c+\mu^-+\nu_x)\lesssim 3.9\cdot10^{-7}-1.4\cdot10^{-7}$.