Dark antiatoms can explain DAMA

TL;DR

This paper proposes that a sub-dominant form of dark matter, composed of dark antiatoms with specific mass and size, can explain the positive DAMA detection signal through binding to thallium, while remaining undetected in other experiments.

Contribution

It introduces a novel dark matter candidate, dark antiatoms, and explains the DAMA results via their binding to thallium, a dopant in the detector.

Findings

Dark antiatoms can bind to high-Z atoms like thallium.

The proposed dark matter interacts via a millicharge due to photon-dark photon mixing.

This model accounts for DAMA's positive signal and null results elsewhere.

Abstract

We show that the existence of a sub-dominant form of dark matter, made of dark antiatoms of mass and size of the order of 1 TeV and 30 fm respectively, can explain the results of direct detection experiments, with a positive signal in DAMA/NaI and DAMA/LIBRA and no signal in other experiments. The signal comes from the binding of the dark antiatoms to thallium, a dopant in DAMA, and is not present for the constituent atoms of other experiments. The dark antiatoms are made of two particles oppositely charged under a dark U(1) symmetry and can bind to terrestrial atoms because of a kinetic mixing between the photon and the massless dark photon, such that the dark particles acquire an electric millicharge of the order of 0.0005e. This millicharge enables them to bind to high-Z atoms via radiative capture, after they thermalize in terrestrial matter through elastic collisions.