Missing in Axion: where are XENON1T's big black holes?

TL;DR

This paper proposes using the black hole mass gap as a new method to constrain particles like axions, showing that axion interactions can lead to heavier black holes within the predicted mass gap.

Contribution

It introduces the black hole mass gap as a novel astrophysical tool for constraining new particles such as axions.

Findings

Axion-like particles can increase black hole masses within the mass gap.

Stellar simulations show axions can explain the XENON1T excess.

Heavier black holes (~56 MS) are consistent with axion models.

Abstract

We pioneer the black hole mass gap as a powerful new tool for constraining new particles. A new particle that couples to the Standard Model---such as an axion---acts as an additional source of loss in the cores of population-III stars, suppressing mass lost due to winds and quenching the pair-instability. This results in heavier astrophysical black holes. As an example, using stellar simulations we show that the solar axion explanation of the recent XENON1T excess implies astrophysical black holes of ~ 56 MS, squarely within the black hole mass gap predicted by the Standard Model.