Searching for Dark Matter with circularly polarised photons from the Galactic Centre

TL;DR

This paper explores the potential of using circularly polarised gamma rays from the Galactic Centre as a novel method to detect dark matter interactions, highlighting the significance of photon polarisation in understanding new physics.

Contribution

It introduces the concept of using circular polarisation of gamma rays as a new probe for dark matter interactions, specifically from fermionic Majorana dark matter in the Galactic Centre.

Findings

Circular polarisation can reach up to 90% in the model.

Polarised gamma rays provide a new signature for dark matter detection.

Detection prospects discussed for future experiments.

Abstract

Conventional indirect dark matter (DM) searches look for an excess in the electromagnetic emission from the sky that cannot be attributed to known astrophysical sources, but its polarisation has not been explored to date. In this proceeding, we argue that photon polarisation is an important feature to understand new physics interactions. In particular, circular polarisation can be generated from Beyond the Standard Model interactions if they violate parity and there is an asymmetry in the number density of the initial state particles which participate in the interaction. We consider a simplified model for fermionic (Majorana) DM and study the circularly polarised gamma rays below 10 GeV from DM cosmic ray electron interactions. We study the differential flux of positive and negative polarised photons from the Galactic Centre and show that the degree of circular polarization can reach up to 90%. Finally, we discuss the detection prospects of this signal in future experiments.