Higgs production from sterile neutrinos at future lepton colliders

TL;DR

This paper explores how sterile neutrinos can enhance Higgs production at future lepton colliders through resonant processes, potentially revealing new physics beyond the Standard Model.

Contribution

It introduces a novel resonant Higgs production mechanism involving heavy sterile neutrinos and assesses the sensitivity of future colliders to this process.

Findings

Neutrino Yukawa couplings below 1% can produce observable effects.

Sensitivity to heavy neutrinos improves with higher collider energies.

Future colliders can detect deviations from the Standard Model due to sterile neutrinos.

Abstract

In scenarios with sterile (right-handed) neutrinos that are subject to an approximate "lepton-number-like" symmetry, the heavy neutrinos (i.e. the mass eigenstates) can have masses around the electroweak scale and couple to the Higgs boson with, in principle, unsuppressed Yukawa couplings while accounting for the smallness of the light neutrinos' masses. In these scenarios, the on-shell production of heavy neutrinos and their subsequent decays into a light neutrino and a Higgs boson constitutes a hitherto unstudied resonant contribution to the Higgs production mechanism. We investigate the relevance of this resonant mono-Higgs production mechanism in leptonic collisions, including the present experimental constraints on the neutrino Yukawa couplings, and we determine the sensitivity of future lepton colliders to the heavy neutrinos. With Monte Carlo event sampling and a simulation of the detector response we find that, at future lepton colliders, neutrino Yukawa couplings below the percent level can lead to observable deviations from the SM and, furthermore, the sensitivity improves with higher center-of-mass energies (for identical integrated luminosities).