Revisiting the Higgs Boson Decay into a Photon and a Neutrino Pair

TL;DR

This paper provides new, concise calculations of the Higgs boson decay into a neutrino pair and a photon, highlighting the impact of non-resonant contributions on high-energy photon regions relevant for dark sector searches.

Contribution

It introduces a simplified one-loop calculation method for the decay rate and analyzes non-resonant effects beyond the narrow width approximation.

Findings

Decay rate $ o$ 1.33 keV, consistent with NWA

Non-resonant box diagrams affect high-energy photon spectrum

Implications for dark sector searches at future colliders

Abstract

We present new calculations of the leading-order one-loop amplitude and the decay rate for $H\to \nu \bar{\nu} \gamma$ within the standard model, employing reduction to a set of basic Passarino-Veltman functions resulting in more concise expressions compared to prior works. Our result for the total decay rate is $\Gamma(H\to \nu\bar{\nu} \gamma)=1.33\,\text{keV}$, in close agreement with the narrow width approximation (NWA) for the intermediate Z boson. A comparison with previous results available in the literature is also provided. We evaluate the differential decay rate with respect to the energy of the photon and find that the non-resonant contributions from box diagrams beyond the NWA notably affect the kinematic region associated with high-energy photons, where the intermediate Z boson is offshell. This suggests potential implications for searches of dark sector mediators, particularly in future lepton collider experiments.