Composite Millicharged Dark Matter

TL;DR

This paper explores a composite millicharged dark matter model with pion-like particles from a QCD-like theory, analyzing two production mechanisms and their phenomenological implications, including potential signals and constraints.

Contribution

It introduces a novel composite millicharged dark matter model with two distinct production scenarios and detailed phenomenological and experimental constraint analysis.

Findings

Potential explanation for the 130 GeV Fermi photon line via dark pion decays

Self-interaction cross section impacts galaxy halo profiles

Constraints from isotope searches are more restrictive than underground detectors

Abstract

We study a composite millicharged dark matter model. The dark matter is in the form of pion-like objects emerging from a higher scale QCD-like theory. We present two distinct possibilities with interesting phenomenological consequences based on the choice of the parameters. In the first one, the dark matter is produced non-thermally and it could potentially account for the 130 GeV Fermi photon line via decays of the "dark pions". We estimate the self-interaction cross section which might play an important role both in changing the dark matter halo profile at the center of the galaxy and in making the dark matter warmer. In the second version the dark matter is produced via the freeze-in mechanism. Finally we impose all possible astrophysical, cosmological and experimental constraints. We study in detail generic constraints on millicharged dark matter that can arise from anomalous isotope searches of different elements and we show why constraints based on direct searches from underground detectors are not generally valid.