Implications of the first AMS-02 measurement for dark matter annihilation and decay

Abstract

In light of the first measurement ofthe positron fraction by the AMS-02 experiment,we perform a detailed global analysis onthe interpretation of the latest data ofPAMELA, Fermi-LAT, and AMS-02 in terms ofdark matter (DM) annihilation and decayin various propagation models.The allowed regions forthe DM particle mass and annihilation cross section or decay life-timeare obtained for channels with leptonic final states:2e, 2μ, 2τ, 4e, 4μ and 4τ.We show thatfor the conventional astrophysical backgroundthe AMS-02 positron fraction data alone favoura DM particle mass ∼ 500(800) GeVif DM particles annihilate dominantly into 2μ(4μ) final states,which is significantly lower than that favoured bythe Fermi-LAT data of the total flux of electrons and positrons.The allowed regions by the two experiments do not overlapat a high confidence level (99.99999%C.L.).We consider a number of propagation models with differenthalo height Zh, diffusion parameters D0 and δ1/2,and power indices of primary nucleon sources γp1/p2.The normalization and the slope of the electron background arealso allowed to vary.We find that the tension between the two experiments canbe only slightly reduced in the propagation model with large Zh and D0.The consistency of fit is improved forannihilation channels with 2τ and 4τ final stateswhich favour TeV scale DM particle with large cross sections above∼ 10−23 cm3s−1.In all the considered leptonic channels,the current data favour the scenario of DM annihilation over DM decay.In the decay scenario,the charge asymmetric DM decay is slightly favoured.