Disentangling axion-like particle couplings to nucleons via a delayed signal in Super-Kamiokande from a future supernova

TL;DR

This paper proposes a method to detect axion-like particles from supernovae via delayed photon signals in water Cherenkov detectors, enabling the study of their couplings to nucleons and distinguishing between proton and neutron interactions.

Contribution

It introduces a novel detection signature for ALPs involving delayed photons from supernovae, allowing for probing specific ALP mass and coupling ranges and disentangling nucleon couplings.

Findings

ALPs produce detectable delayed photons in Super-Kamiokande.

Parameter space for ALP mass and coupling can be constrained.

Disentangling ALP-proton and ALP-neutron couplings is feasible.

Abstract

In this work, we show that, if axion-like particles (ALPs) from core-collapse supernovae (SNe) couple to protons, they would produce very characteristic signatures in neutrino water Cherenkov detectors through their scattering off free protons via $a \, p \rightarrow p \, \gamma$ interactions. Specifically, sub-MeV ALPs would generate photons with energies $\sim 30$ MeV, which could be observed by Super-Kamiokande and Hyper-Kamiokande as a delayed signal after a future detection of SN neutrinos. We apply this to a hypothetical neighbouring SN (at a maximum distance of 100 kpc) and demonstrate that the region in the parameter space with ALP masses between $10^{-4}$ MeV and $1$ MeV and ALP-proton couplings in the range $3 \times 10^{-6}-4 \times 10^{-5}$ could be probed. We argue that this new signature, combined with the one expected at $\sim 7$ MeV from oxygen de-excitation, would allow us to disentangle ALP-neutron and ALP-proton couplings.