A solar origin of the XENON1T excess without stellar cooling problems

TL;DR

The paper proposes a dark photon model with a $Z_2$ symmetry that explains the XENON1T excess without conflicting with stellar cooling constraints, and predicts new testable particles at sub-TeV energies.

Contribution

It introduces a novel effective field theory with a $Z_2$ symmetry that suppresses stellar cooling issues while accounting for the XENON1T excess.

Findings

The $Z_2$ symmetry forbids dark photon emission in dense stars.

The model explains the XENON1T excess through spontaneous $Z_2$ breaking.

Predicted new charged particles can be tested in laboratory experiments.

Abstract

Solar interpretations of the recent XENON1T excess events, such as axion or dark photon emissions from the sun, are thought to be at odds with stellar cooling bounds from the horizontal branch stars and red giants. We propose a simple effective field theory of a dark photon in which a $Z_2$ symmetry forbids a single dark photon emission in the dense stars, thereby evading the cooling bounds, while the $Z_2$ is spontaneously broken in the vacuum and sun, thereby explaining the XENON1T excess. The scalar responsible for the $Z_2$ breaking has an extremely flat potential, but the flatness can be maintained under quantum corrections. The UV completion of the EFT generally requires the existence of new electrically charged particles with sub-TeV masses with $O(1)$ couplings to the dark photon, offering the opportunity to test the scenario further and opening a new window into the dark sector in laboratory experiments.