PAMELA/ATIC anomaly from the meta-stable extra dark matter component and the leptophilic Yukawa interaction
Abstract
We present a supersymmetric model with two dark matter (DM) components explaining the galactic positron excess observed by PAMELA/HEAT and ATIC/PPB-BETS: One is the conventional (bino-like) lightest supersymmetric particle (LSP) , and the other is a TeV scale meta-stable neutral singlet ND, which is a Dirac fermion (N,Nc). In this model, ND decays dominantly into e+e- through an R parity preserving dimension 6 operator with the life time τN 1026 sec. We introduce a pair of vector-like superheavy SU(2) lepton doublets (L,Lc) and lepton singlets (E,Ec). The dimension 6 operator leading to the ND decay is generated from the leptophilic Yukawa interactions by W⊃ NecE+LhdEc+m3/2l1Lc with the dimensionless couplings of order unity, and the gauge interaction by L⊃ 2 g'ec*ec + h.c. The superheavy masses of the vector-like leptons (ML, ME 1016 GeV) are responsible for the longevity of ND. The low energy field spectrum in this model is just the MSSM fields and ND. Even for the case that the portion of ND is much smaller than that of in the total DM density [ O(10-10) nND/n], the observed positron excess can be explained by adopting relatively lighter masses of the vector-like leptons (1013 GeV ML,E 1016 GeV). The smallness of the electron mass is also explained. This model is easily embedded in the flipped SU(5) grand unification, which is a leptophilic unified theory.