Search for Heavy Neutrino in K->mu nu_h(nu_h-> nu gamma) Decay at ISTRA+ Setup

TL;DR

This study searches for heavy neutrinos in kaon decays, setting upper limits on their mixing parameters within specific mass and lifetime ranges, thereby constraining new physics models involving neutrino properties.

Contribution

It provides the first experimental upper limits on heavy neutrino mixing in the specified mass and lifetime range using the ISTRA+ setup.

Findings

Upper limits on |U_mu_h|^2: 5 x 10^{-5} (Majorana), 8 x 10^{-5} (Dirac)

Mass range 30-80 MeV/c^2 for heavy neutrinos

Lifetime range 10^{-11} to 10^{-9} seconds

Abstract

Heavy neutrino nu_h with m_h < 300MeV/c^2 can be effectively searched for in kaon decays. We put upper limits on mixing matrix element |U_mu_h}|^2 for radiatively decaying nu_h from K->mu nu_h (nu_h -> nu gamma) decay chain in the following parameter region: 30MeV/c^2 < m_h < 80MeV/c^2; 10^{-11}sec < tau_h < 10^{-9}sec. For the whole region |U_{mu h}|^2 < 5 x 10^{-5} for Majorana type of nu_h and | U_{\mu h}|^2 < 8 x 10^{-5} for the Dirac case.