A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton

TL;DR

This study utilizes XMM-Newton data to search for unknown spectral emission lines in the diffuse X-ray background, aiming to detect signals from potential dark matter candidates like sterile neutrinos or axions.

Contribution

It introduces a novel analysis method combining high-exposure X-ray data and posterior predictive p-value analysis to improve constraints on dark matter decay signals.

Findings

No definitive detection of new emission lines was made.

Significantly improved upper limits on sterile neutrino and axion parameters.

Enhanced constraints help narrow down viable dark matter models.

Abstract

The Standard Model of particle physics can be extended to include sterile (right-handed) neutrinos or axions to solve the dark matter problem. Depending upon the mixing angle between active and sterile neutrinos, the latter have the possibility to decay into monoenergetic active neutrinos and photons in the keV-range while axions can couple to two photons. We have used data taken with X-ray telescopes like e.g. XMM-Newton for the search of line emissions. We used pointings with high exposures and expected dark matter column densities with respect to the dark matter halo of the Milky Way. The posterior predictive p-value analysis has been applied to locate parameter space regions which favour additional emission lines. In addition, upper limits of the parameter space of the models have been generated such that the preexisting limits have been significantly improved.