Probing a diffuse flux of axion-like particles from galactic supernovae with neutrino water Cherenkov detectors

In this article, we claim that axion-like particles (ALPs) with MeV masses can be produced with semi-relativistic velocities in core-collapse supernovae (SNe), generating a diffuse galactic flux. We show that these ALPs can be detected in neutrino water Cherenkov detectors via $ap\to p\gamma$ interactions. Using Super-Kamiokande data, we derive new constraints on the ALP parameter space, excluding a region spanning one order of magnitude in the ALP-proton coupling above cooling bounds for ALP masses in the range of $1-70$~MeV and ALP-proton couplings between $\sim 2\times {10}^{-5}-2\times {10}^{-4}$. We show that the future Hyper-Kamiokande will be able to probe couplings as small as $\sim {10}^{-5}$, considerably constraining the allowed region above SN 1987A cooling bounds.