Abstract
We revisit dark matter annihilation as an explanation of the positron excess reported recently by the AMS-02 satellite-borne experiment. To this end, we propose a particle dark matter model by considering a Two Higgs Doublet Model (2HDM) extended with an additional singlet boson and a singlet fermion. The additional (light) boson mixes with the pseudoscalar inherent in the 2HDM, and the singlet fermion, which is the dark matter candidate, annihilates via this bosonic portal. The dark matter candidate is made leptophilic by choosing the lepton-specific 2HDM and a suitable high value of $\tan\beta$. We identify the model parameter space which explains the muon g-2 anomaly while evading the experimental constraints. After establishing the viability of the singlet fermion to be a dark matter candidate, we calculate the positron excess produced from its annihilation to the light bosons which primarily decay to muons. Incorporating the Sommerfeld effect caused by the light mediator and an appropriate boost factor, we find that our proposed model can satisfactorily explain the positron fraction excess as well as the positron spectrum data reported by AMS-02 experiment.
Highlights
The existence of dark matter in the Universe has been established principally through their gravitational effects and its amount in the Universe has been well determined by the PLANCK observations [1]
Incorporating the Sommerfeld effect caused by the light mediator and an appropriate boost factor, we find that our proposed model can satisfactorily explain the positron fraction excess as well as the positron spectrum data reported by the AMS-02 experiment
The AMS-02 experiment onboard the International Space Station reported an excess of positron fraction beyond the positron energy of 10 GeV
Summary
The existence of dark matter in the Universe has been established principally through their gravitational effects and its amount in the Universe has been well determined by the PLANCK observations [1]. The indirect detection of dark matter is based on the principle of detecting Standard Model particles produced due to the self-annihilation of dark matter in a suitable environment These annihilation products can appear as the excess of the expected flux which could not be explained by other known astrophysical processes. The Sommerfeld enhanced annihilation to quarks and leptons are strongly constrained using the measurements of cosmic microwave background radiation (CMB) anisotropies by PLANCK [1] and the dwarf galaxy results from Fermi-LAT [27] Such a difficulty can be circumvented by making the singlet boson leptophilic and forbidding the tau final state kinematically.
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