Search for heavy neutral leptons in B-meson decays

TL;DR

This paper reports a search for long-lived heavy neutral leptons in B-meson decays at the LHCb experiment, setting new constraints on their mixing with muon neutrinos within a specific mass range.

Contribution

First search for heavy neutral leptons in B-meson decays at 13 TeV LHCb data, providing new limits on their mixing parameters.

Findings

No significant excess observed.

Constraints on |U_{μN}|^2 in the 1.6-5.5 GeV mass range.

Limits improve previous bounds in this mass window.

Abstract

A search for long-lived heavy neutral leptons produced in B-meson decays and decaying to a $ \mu^\pm \pi^\mp$ final state is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5\,\mathrm{fb}^{-1}$. The results are interpreted in both lepton-number-conserving and lepton-number-violating scenarios. No significant excess is observed. Constraints are placed on the squared mixing element $|U_{\mu N}|^2$ to the active muon neutrino, under the assumption that couplings to other lepton flavours are negligible, in the mass range of $1.6$-$5.5$ GeV.