What if ALP dark matter for the XENON1T excess is the inflaton

TL;DR

This paper explores the possibility that the axion-like particle (ALP) dark matter, which explains the XENON1T excess, could also have served as the inflaton, linking dark matter and early universe inflation.

Contribution

It proposes a unified scenario where the ALP responsible for the XENON1T excess also drove cosmic inflation, connecting dark matter properties with inflationary dynamics.

Findings

ALP mass and decay constant are consistent with inflationary predictions.

The scenario links dark matter properties to the inflationary energy scale.

Implications for the universe's thermal history after inflation.

Abstract

The recent XENON1T excess in the electron recoil data can be explained by anomaly-free axion-like particle (ALP) dark matter with mass $m_\phi = 2.3 \pm 0.2\,$keV and the decay constant $f_\phi/q_e \simeq 2 \times 10^{10} \sqrt{\Omega_\phi/\Omega_{\rm DM}}\,{\rm GeV}$. Intriguingly, the suggested mass and decay constant are consistent with the relation, $f_\phi \sim 10^3 \sqrt{m_\phi M_p}$, predicted in a scenario where the ALP plays the role of the inflaton. This raises a possibility that the ALP dark matter responsible for the XENON1T excess also drove inflation in the very early universe. We study implications of the XENON1T excess for the ALP inflation and thermal history of the universe after inflation.