# Detectability of Collective Neutrino Oscillation Signatures in the Supernova Explosion of a 8.8 $M_\odot$ star

## TL;DR

This study simulates collective neutrino oscillations in a supernova from an 8.8 solar mass star, demonstrating that upcoming detectors like Hyper-Kamiokande and DUNE can identify CNO effects up to 10 kpc, aiding supernova neutrino analysis.

## Contribution

First detailed simulation of CNO effects in a supernova from a low-mass progenitor, assessing detectability with future neutrino observatories.

## Key findings

- CNO effects commence after ~100 ms post bounce.
- Hyper-Kamiokande can detect CNO signatures up to 10 kpc in inverted hierarchy.
- DUNE can detect CNO signatures up to 10 kpc in normal hierarchy.

## Abstract

In order to investigate the impact of collective neutrino oscillations (CNO) on the neutrino signal from a nearby supernova, we perform 3-flavor neutrino oscillation simulations employing the multiangle effect. The background hydrodynamic model is based on the neutrino hydrodynamic simulation of a 8.8 \Msun progenitor star. We find that CNO commences after some 100 ms post bounce. Before this, CNO is suppressed by matter-induced decoherence. In the inverted mass hierarchy, the spectrum of $\bar{\nu}_e$ becomes softer after the onset of CNO. To evaluate the detectability of this modification, we define a hardness ratio between the number of high energy neutrino events and low energy neutrino events adopting a fixed critical energy. We show that Hyper-Kamiokande (HK) can distinguish the effect of CNO for supernova distances out to $\sim 10$ kpc. On the other hand, for the normal mass hierarchy, the spectrum of $\nu_e$ becomes softer after the onset of CNO, and we show that DUNE can distinguish this feature for supernova distances out to $\sim 10$ kpc. More work is necessary to optimize the best value of critical energy for maximum sensitivity. We also show that if the spectrum of $\bar{\nu}_e$ in HK becomes softer due to CNO, the spectrum of $\nu_e$ in DUNE becomes harder, and vice versa. This synergistic observations in $\bar{\nu}_e$ and $\nu_e$, by HK and DUNE respectively, will be an intriguing opportunity to test the occurrence of CNO.