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

TL;DR

This paper estimates decay rates of heavy baryons involving sterile neutrinos, highlighting their potential for detection in experiments and comparing their production to mesons, with implications for current experimental bounds.

Contribution

It provides the first tree-level estimates of heavy baryon decay branching ratios into sterile neutrinos, emphasizing their significance in sterile neutrino searches.

Findings

Charmed baryons are less promising for sterile neutrino searches than mesons.

Beauty baryons have comparable sterile neutrino production rates to beauty mesons.

Current experimental bounds constrain certain heavy baryon decay branching ratios to sterile neutrinos.

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 ${\rm Br}(\Lambda_b\to\Lambda_c+\mu^-+\nu_x)\lesssim 3.9\cdot10^{-7}-1.4\cdot10^{-7}$.