Search for heavy neutrino in $K^{+} \to \mu^{+} \nu_{H}$ decay

TL;DR

This study used high-statistics data from the OKA experiment to search for heavy neutrinos in kaon decays, setting upper limits on their existence in a specific mass range.

Contribution

First search for stable heavy neutrinos in $K^{+}$ decays using missing mass analysis with high-statistics data.

Findings

No peaks observed in missing mass spectrum.

Upper limits set on branching ratio and mixing element $|U_{A H}|^{2}$.

Excluded heavy neutrino masses between 220 and 375 MeV/c².

Abstract

A high statistics data sample of the $K^{+}\to\mu^{+}\nu_{\mu}$ decay was accumulated by the OKA experiment in 2012. The missing mass analysis was performed to search for the decay channel $K^{+}\to\mu^{+}\nu_{H}$ with a hypothetic stable heavy neutrino in the final state. The obtained missing mass spectrum does not show peaks which could be attributed to existence of stable heavy neutrinos in the mass range (220 $< m_{\nu_{H}} <$ 375) MeV$/c^{2}$. As a result, we obtain upper limits on the branching ratio and on the value of the mixing element $|U_{\mu H}|^{2}$.