PAMELA/ATIC anomaly from exotic mediated dark matter decay

Abstract

We discuss dark matter decay mediated by exotically charged particles (exotics) in a supersymmetric model with two dark matter (DM) components: One is the (bino-like) lightest supersymmetric particle (LSP) \chi, and the other is a newly introduced meta-stable neutral singlet $N$. $N$ decays to \chi e^+e^- via a dimension 6 operator induced by a penguin-type one loop diagram with the life time of 10^{26} sec., explaining energetic cosmic e^\pm excess observed recently by PAMELA and ATIC/PPB-BETS. The superheavy masses of exotics (\sim 10^{15-16} GeV) are responsible for the longevity of $N$. The superpartner of $N$ develops the vacuum expectation value (VEV) of order TeV so that the DM $N$ achieves the desired mass of 2 TeV. By the VEV, the U(1)_R symmetry is broken to the discrete Z_2 symmetry, which is identified with the matter parity in the minimal supersymmetric standard model (MSSM). Since we have the two DM components, even extremely small amount of $N$ [O(10^{-10}) < (n_N/n_\chi)] could account for the observed positron flux with relatively light exotics' masses [10^{12} GeV < M_{exo.} < 10^{16} GeV].