Decaying WIMP dark matter for AMS-02 cosmic positron excess

TL;DR

This paper proposes a model where heavy, thermally produced decaying dark matter explains the AMS-02 cosmic positron excess, involving a new Z_2 symmetry and non-renormalizable decay operators within a gauged vector-like lepton framework.

Contribution

It introduces a novel decaying dark matter scenario with a new Z_2 symmetry, compatible with thermal production and leptonic decay channels, within a gauged vector-like lepton model.

Findings

Explains the positron excess with decaying dark matter of 700 GeV to 3 TeV.

Ensures dark matter stability and decay via a new Z_2 symmetry and suppressed operators.

Aligns dark matter relic density with cosmological observations.

Abstract

For explaining the AMS-02 cosmic positron excess, which was recently reported, we consider a scenario of thermally produced and decaying dark matter (DM) into the standard model (SM) leptons with an extremely small decay rate, \Gamma_{DM} \sim 10^{-26} sec.^{-1}. Since the needed DM mass is relatively heavy (700 GeV < m_{DM} < 3000 GeV), we introduce another DM component apart from the lightest supersymmetric particle ("LSP"). For its (meta-) stability and annihilation into other particles, the new DM should be accompanied with another Z_2 symmetry apart from the R-parity. Sizable renormalizable couplings of the new DM with SM particles, which are necessary for its thermalization in the early universe, cannot destabilize the new DM because of the new Z_2 symmetry. Since the new DM was thermally produced, it can naturally explain the present energy density of the universe. The new DM can decay into the SM leptons (and the LSP) only through non-renormalizable operators suppressed by a superheavy squared mass parameter after the new symmetry is broken around TeV scale. We realize this scenario in a model of "gauged vector-like leptons," which was proposed recently for the naturalness of the Higgs boson.