Leptophilic Dark Matter and AMS-02 Cosmic-ray Positron Flux

Abstract: With the measurement of positron flux published recently by AMS-02 collaboration, we show how the leptophilic dark matter fits the observation. We obtain the percentages of different products of dark matter annihilation that can best describe the flux of high energy positrons observed by AMS. We show that dark matter annihilates predominantly into $\tau\tau$ pair, while both $ee$ and $\mu\mu$ final states should be less than $20\%$. When gauge boson final states are included, the best branching ratio of needed $\tau\tau$ mode reduces.