Probing heavy neutrinos in the COMET experiment

TL;DR

The paper proposes using the COMET experiment, primarily designed for muon-electron conversion, to search for heavy neutrinos in the 1 MeV to 100 MeV mass range through their production and decay signatures.

Contribution

It introduces a novel application of the COMET experiment to search for heavy neutrinos, expanding its scientific scope beyond its original purpose.

Findings

Sensitivity comparable to PS191 bound with 10^17 muons

Heavy neutrinos can be produced via active-sterile mixing

Decay to electron-positron pairs provides detectable signals

Abstract

We argue that the COMET experiment --- a dedicated experiment for the $\mu$-$e$ conversion search --- can be a powerful facility to search for heavy neutrinos in the mass range $1\,{\rm MeV} \lesssim M \lesssim 100\,{\rm MeV}$. The stopped muons captured by the target nuclei or decaying in orbit are efficiently produce heavy neutrinos via the active-sterile mixing. The produced heavy neutrinos then decay to electron-positron pair (plus an active neutrino), which events are clearly seen by the cylindrical drift chamber surrounding the target. The expected sensitivity is comparable to the PS191 bound when the COMET experiment achieves $\sim 10^{17}$ stopping muons in the target.