Neutrino non-radiative decay in matter: constraints and prospects

TL;DR

This paper derives new bounds on neutrino-Majoron couplings from supernova neutrino observations and explores future detection prospects, showing potential for significantly improved constraints and impacts on the diffuse supernova neutrino background.

Contribution

It introduces novel bounds on neutrino-Majoron couplings using supernova data and assesses future detection capabilities with detailed simulations.

Findings

Current bounds can be improved by future supernova observations.

Neutrino decay significantly affects the diffuse supernova neutrino background.

Future detectors could tighten constraints on neutrino-Majoron couplings.

Abstract

Neutrinos, being massive, can decay. A heavier neutrino could decay into a lighter one and a massless scalar or pseudoscalar boson, such as the Majoron. Two-body non-radiative decay could occur in dense matter, such as in the inner dense regions of a core-collapse supernova. We first derive novel bounds on neutrino-Majoron couplings using the spectral distortions induced by neutrino non-radiative two-body decay in matter, and two-dimensional likelihood analyses of the 24 $\bar{\nu}_e$ events from SN1987A. We then explore the prospects of neutrino-Majoron couplings from a future galactic core-collapse supernova, leaving either a neutron star or a black-hole. To this aim, we use information from detailed one-dimensional supernova simulations. We consider the supernova neutrino signal associated with inverse-beta decay in the upcoming JUNO and Hyper-Kamiokande detectors, with neutrino-argon scattering in DUNE, or with coherent neutrino-nucleus scattering in the DARWIN experiment. In a full 3$\nu$ framework, based on the spectral distortions induced by neutrino decay in matter, we perform two-dimensional likelihood analyses and provide prospects for the limits on neutrino-Majoron couplings. Our results show that the observation of a future supernova will significantly improve on the current bounds, in particular from SN1987A and neutrinoless double-beta decay. Finally, we explore the impact of neutrino decay in matter on the diffuse supernova neutrino background formed by past supernova explosions. We show for the first time that the effects on black-hole contributions are important and modify the DSNB number of events by several tens of percent in Hyper-Kamiokande.