Hadronic Probes of Non-Standard Neutrino Interactions

TL;DR

This paper investigates how hadronic leptonic decays can detect light neutrinophilic scalars that enhance neutrino self-interactions, offering a new way to probe non-standard neutrino physics with upcoming experiments.

Contribution

It provides detailed calculations of spectral distortions in hadronic decays caused by light scalars, and assesses the sensitivity of future experiments to these mediators.

Findings

Spectral tails in decays signal light neutrinophilic scalars.

Projected sensitivities of PIONEER and BeEST are promising.

Hadron decay experiments can effectively probe non-standard neutrino interactions.

Abstract

In this work, we study leptonic decays of hadrons as probes of light neutrinophilic scalars that mediate enhanced neutrino self-interactions. Such scalars can be emitted in processes involving neutrinos, turning two-body decays into three-body final states and producing characteristic spectral distortions. We compute these effects for charged pion decay and nuclear electron capture decay, including both on-shell and off-shell scalar emission, as well as the loop-induced renormalization required to cancel divergences. Using these results, we derive the projected sensitivity of PIONEER and assess the current and future reach of BeEST. The resulting low-energy spectral tails provide a characteristic signal for light neutrinophilic scalars, making upcoming hadron decay experiments powerful probes of light mediators of non-standard neutrino self-interactions.