Heavy neutrino searches and NA62 status

TL;DR

This paper reports on searches for heavy neutrinos using the NA62 experiment's data, setting new limits on their properties, and provides an update on the experiment's progress towards measuring rare kaon decays.

Contribution

It presents the first limits on heavy neutrino mixing from NA62 data and updates on the experiment's status and future measurements.

Findings

No signal observed for heavy neutrinos, setting new upper limits.

Reported on the progress of the upgraded NA62 experiment since 2015.

Established constraints on the branching ratio of $K^+ o u_h o ext{decay}$ processes.

Abstract

The NA62 experiment at CERN SPS recorded in 2007 a large sample of $K^+\to\mu^+\nu_\mu$ decays. A peak search in the missing mass spectrum of this decay is performed. In the absence of observed signal, the limits obtained on $\mathcal{B}(K^+\to\mu^+\nu_h)$ and on the mixing matrix element $|U_{\mu4}|^2$ are reported. The upgraded NA62 experiment started data taking in 2015, with the aim of measuring the branching fraction of the $K+\to\pi^+\nu\bar{\nu}$ decay. An update on the status of the experiment is presented.