Axion signatures from supernova explosions through the nucleon electric-dipole portal

Understand

We consider axions coupled to nucleons and photons only through the nucleon electric-dipole moment (EDM) portal.

• This coupling is a model-independent feature of QCD axions, which solve the strong CP problem, and might arise as well in more general axion-like particle setups.
• We revise the supernova (SN) axion emission induced by the nucleon EDM coupling and refine accordingly the SN 1987A bound.
• Furthermore, we calculate the axion flux from a future Galactic SN and show that it might produce a peculiar and potentially detectable gamma-ray signal in a large underground neutrino detector such as the proposed Hyper-Kamiokande.