Parameters in a class of leptophilic dark matter models from PAMELA, ATIC and FERMI

In this work we study a class of leptophilic dark matter models, where the dark matter interacts with the standard model particles via the U(1)Li−LjU(1)Li−Lj gauge boson, to explain the e±e± excess in cosmic rays observed by ATIC and PAMELA experiments, and more recently by Fermi experiment. There are three types of U(1)Li−LjU(1)Li−Lj models: (a) U(1)Le−LμU(1)Le−Lμ, (b) U(1)Le−LτU(1)Le−Lτ, and (c) U(1)Le−LτU(1)Le−Lτ. Although ATIC or Fermi data are consistent with PAMELA data separately, ATIC and Fermi data do not agree with each other. We therefore aim to identify which of the three models can explain which data set better. We find that models (a) and (b) can give correct dark matter relic density and explain the ATIC and PAMELA data simultaneously recur to the Breit–Wigner enhancement. Whereas model (c) with a larger Z′Z′ mass can explain Fermi and PAMELA data simultaneously. In all cases the model parameters are restricted to narrow regions. Future improved data will decide which set of data is correct and also help to decide the correct dark matter model.