Thursday, July 25, 2013

1307.6204 (P. S. Bhupal Dev et al.)

Neutrino Mass and Dark Matter in light of recent AMS-02 results    [PDF]

P. S. Bhupal Dev, Dilip Kumar Ghosh, Nobuchika Okada, Ipsita Saha
We study a simple extension of the Standard Model supplemented by an electroweak triplet scalar field to accommodate small neutrino masses by type-II seesaw mechanism, while an additional singlet scalar field can play the role of cold dark matter (DM) in the Universe. This DM candidate is naturally leptophilic, and for DM masses above the seesaw scale, the lepton flux due to its annihilation carries information about the neutrino mass hierarchy. Using the recently released high precision data on positron fraction and flux from AMS-02 experiment and assuming a DM interpretation of the observed excess, we show that a good fit to the AMS-02 data can be obtained in our model only for a normal hierarchical neutrino mass spectrum, while the inverted hierarchy case is strongly disfavored. We also find that the model predictions for excess photon and neutrino fluxes while simultaneously satisfying the AMS-02 positron excess are consistent with the current limits on the inclusive photon flux from Fermi-LAT and on the neutrino flux from IceCube respectively. Moreover, the absence of an excess anti-proton flux as suggested by PAMELA results, sets an indirect upper limit on the DM-nucleon spin-independent elastic scattering cross section in our model which is stronger than the existing DM direct detection bound from XENON100 in the AMS-02 preferred DM mass range.
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