Universally Leptophilic Dark Matter From Non-Abelian Discrete Symmetry

TL;DR

This paper proposes a non-Abelian discrete symmetry framework that ensures leptophilic dark matter decays predominantly into leptons, aligning with cosmic-ray positron anomaly observations and avoiding harmful decay operators.

Contribution

It introduces a model using A_4 symmetry to prohibit lower-dimensional decay operators, ensuring flavor-blind leptonic decay consistent with experimental data.

Findings

Dark matter decays mainly into leptons with a lifetime of ~10^26 seconds.

The model aligns with PAMELA and Fermi-LAT cosmic-ray data.

The symmetry also has implications for neutrino physics.

Abstract

The positron anomaly recently reported by the cosmic-ray measurements can be explained by the decaying dark matter scenario, where it decays mainly into leptons with the lifetime of O(10^26) second. When the dark matter is a fermionic particle, the lifetime of this order is known to be obtained by a dimension 6 operator suppressed by the unification scale 10^16 GeV, while such decay operators do not necessarily involve only leptons. In addition, the scenario would be spoiled if there exist lower-dimensional operators inducing the dark matter decay. We show in this letter that a single non-Abelian discrete symmetry such as A_4 is possible to prohibit all such harmful (non-leptonically coupled and lower-dimensional) operators. Moreover, the dark matter decays into charged leptons in a flavor-blind fashion due to the non-Abelian flavor symmetry, which results in perfect agreements not only with the PAMELA data but also with the latest Fermi-LAT data reported very recently. We also discuss some relevance between the discrete symmetry and neutrino physics.