Dynamical Dark Matter and the Positron Excess in Light of AMS

TL;DR

This paper shows that Dynamical Dark Matter can explain the AMS positron excess with lighter particles and simple decays, predicting a plateau in the positron fraction up to 1 TeV as a key signature.

Contribution

It demonstrates that DDM models can fit AMS data with lighter constituents and simple decays, challenging previous assumptions about dark matter decay complexity.

Findings

DDM can match AMS positron data with lighter particles.

A positron fraction plateau at ~1 TeV is predicted as a DDM signature.

The model remains consistent with FERMI and Planck constraints.

Abstract

The AMS-02 experiment has recently released data which confirms a rise in the cosmic-ray positron fraction as a function of energy up to approximately 350 GeV. Over the past decade, attempts to interpret this positron excess in terms of dark-matter decays have become increasingly complex and have led to a number of general expectations about the decaying dark-matter particles: such particles cannot undergo simple two-body decays to leptons, for example, and they must have rather heavy TeV-scale masses. In this paper, by contrast, we show that Dynamical Dark Matter (DDM) can not only match existing AMS-02 data on the positron excess, but also accomplish this feat with significantly lighter dark-matter constituents undergoing simple two-body decays to leptons. Moreover, we demonstrate that this can be done without running afoul of numerous other competing constraints from FERMI and Planck on decaying dark matter. Finally, we demonstrate that the Dynamical Dark Matter framework makes a fairly robust prediction that the positron fraction should level off and then remain roughly constant out to approximately 1 TeV, without experiencing any sharp downturns. Indeed, if we interpret the positron excess in terms of decaying dark matter, we find that the existence of a plateau in the positron fraction at energies less than 1 TeV may be taken as a "smoking gun" of Dynamical Dark Matter.