Probing the neutrino mass through semileptonic meson decays

TL;DR

This paper proposes that analyzing semileptonic meson decays can reveal the presence and mass of neutrinos, especially distinguishing between left- and right-handed interactions, by examining the forward-backward asymmetry.

Contribution

It introduces a method to test neutrino mass and chirality via decay asymmetries, providing explicit calculations for pseudoscalar and vector meson decays.

Findings

Forward-backward asymmetry is zero for massless neutrinos with left-handed interactions.

Non-zero asymmetry indicates a heavy neutrino or right-handed interactions.

Explicit analysis for pseudoscalar and vector meson decay channels.

Abstract

We argue that a detailed analysis of semileptonic decays can test the possibility of a massive neutrino. The key observable, related to the forward-backward asymmetry, is exactly zero for a massless neutrino but becomes non-zero if the neutral lepton is heavy and interacts with Standard Model fields via left-handed operators. For right-handed interactions, this quantity differs significantly from zero even for a massless right-handed neutrino. We demonstrate this explicitly using the example of a pseudoscalar meson decaying into another pseudoscalar meson. A similar discussion applies to decays into a vector meson, with an additional subtlety addressed in this work.