# Visible neutrino decay in the light of appearance and disappearance long baseline experiments

## TL;DR

This paper explores constraints on neutrino decay involving Majorons using MINOS and T2K data, introducing visible decay effects that enhance the sensitivity of long-baseline experiments to decay parameters.

## Contribution

It presents the first analysis including visible decay contributions in neutrino decay constraints from long-baseline experiments, improving bounds on decay parameters by an order of magnitude.

## Key findings

- Visible decay improves constraints on neutrino decay parameters.
- Decay parameter α constrained to less than 10^{-5} eV^2 at 90% C.L.
- Results apply to both scalar and pseudoscalar Majoron couplings.

## Abstract

We investigate the present constraints from MINOS and T2K experiments for the neutrino decay scenario induced by non-diagonal couplings of Majorons to neutrinos. As novelty, on top of the typical invisible decay prescription, we add the contribution of visible decay, where final products can be observed. This new effect depends on the nature of the neutrino - Majoron coupling, which can be of scalar or pseudoscalar type. Using the combination of disappearance data from MINOS and disappearance and appearance data from T2K, for normal ordering, we constrain the decay parameter $\alpha\equiv E\,\Gamma$ for the heaviest neutrino, where $E$ and $\Gamma$ are the neutrino energy and width, respectively. We find that when considering visible decay within appearance data, one can improve current neutrino long-baseline constraints up to $\alpha< \mathcal{O}(10^{-5})$ eV$^2$, at 90\% C.L., for both kinds of couplings, which is better by one order of magnitude compared to previous bounds.