# Probing Non-Standard Neutrino Interactions with Supernova Neutrinos at Hyper-K

## TL;DR

This paper explores how future supernova neutrino observations at Hyper-Kamiokande could constrain non-standard neutrino self-interactions, which might significantly alter neutrino fluxes and flavor evolution in supernovae, depending on the mass hierarchy and interaction type.

## Contribution

It presents a detailed simulation framework to assess Hyper-Kamiokande's sensitivity to non-standard neutrino self-interactions during a galactic supernova event.

## Key findings

- Hyper-K can constrain flavor-violating NSSI down to ~0.1 G_F in inverted hierarchy.
- Sensitivity depends on neutrino mass hierarchy and NSSI flavor-violation.
- Deviations from no NSSI detectable if NSSI is particularly strong.

## Abstract

Non-standard neutrino self interactions (NSSI) could be stronger than Fermi interactions. We investigate the ability to constrain these four-neutrino interactions by their effect on the flux of neutrinos originating from a galactic supernova. In the dense medium of a core collapse supernova, these new self interactions can have a significant impact on neutrino oscillations, leading to changes at the flavor evolution and spectra level. We use simulations of the neutrino flux from a 13 solar mass, core collapse supernova at 10 kpc away, and numerically propagate these neutrinos through the stellar medium taking into account vacuum/MSW oscillations, SM $\nu-\nu$ scattering as well as $\nu-\nu$ interactions that arise from NSSI. We pass the resulting neutrino flux to a simulation of the future Hyper-Kamiokande detector to see what constraints on NSSI parameters are possible when the next galactic supernova becomes visible. We find that these constraints depend strongly on the neutrino mass hierarchy and if the NSSI is flavor-violating or preserving. Sensitivity to NSSI in the normal hierarchy (NH) at Hyper-K is limited by the experiment's ability to efficiently detect $\nu_{e}$, but deviations from no NSSI could be seen if the NSSI is particularly strong. In the inverted hierarchy (IH) scenario, Hyper-K can significantly improve constraints on flavor-violating NSSI down to $\mathcal{O}(10^{-1})G_{F}$.