Dark Matter Capture in a Core-Collapse Supernova Revives Dark Photons

TL;DR

This paper investigates how dark matter captured inside a star before a supernova can influence dark photon emission, potentially weakening existing stellar cooling constraints and revealing new parameter space for dark sector particles.

Contribution

It introduces a self-consistent analysis of dark matter effects on supernova cooling bounds, highlighting the role of asymmetric dark matter in modifying dark photon constraints.

Findings

Asymmetric dark matter can form a dark photosphere, suppressing dark photon emission.

Dark matter capture can reopen previously excluded dark photon parameter regions.

Equilibrium density of annihilating dark matter is too small to affect bounds significantly.

Abstract

Core-collapse supernovae serve as powerful probes of light, weakly coupled particles, such as dark photons. The conventional SN1987A cooling bound constrains the dark photon mass-mixing parameter space by requiring that the luminosity from the proto-neutron star core not exceed the observed neutrino emission. In this work, we revisit these limits by including the effect of dark matter (DM) captured inside the progenitor star before collapse. The trapped DM acts as an additional scattering target for dark photons, modifying their free-streaming length and, consequently, the supernova cooling rate. We perform a self-consistent analysis for both annihilating and asymmetric DM scenarios, incorporating light-mediator effects in the capture rate calculation. For annihilating DM, the equilibrium density remains too small to affect the bounds significantly. In contrast, asymmetric DM can accumulate to large densities, leading to the formation of a "dark photosphere" that suppresses the dark-photon luminosity and reopens previously excluded regions of parameter space. Our results emphasise the importance of accounting for astrophysical DM populations when deriving stellar-cooling constraints on dark sectors.