Inert Dark Matter in Type-II Seesaw

Abstract

Weakly interacting massive particle (WIMP) as a dark matter (DM) candidate is further inspired by recent AMS-02 data, which confirm the excess of positron fraction observed earlier by PAMELA and Fermi-LAT experiments. Additionally, the excess of positron+electron flux is still significant in the measurement of Fermi-LAT. For solving the problems of massive neutrinos and observed excess of cosmic-ray, we study the model with an inert Higgs doublet (IHD) in the framework of type-II seesaw model by imposing a $Z_2$ symmetry on the IHD, where the lightest particle of IHD is the DM candidate and the neutrino masses originate from the Yukawa couplings of Higgs triplet and leptons. We calculate the cosmic-ray production in our model by using three kinds of neutrino mass spectra, which are classified by normal ordering, inverted ordering and quasi-degeneracy. We find that when the constraints of DM relic density and comic-ray antiproton spectrum are taken into account, the observed excess of positron/electron flux could be explained well in normal ordered neutrino mass spectrum. Moreover, excess of comic-ray neutrinos is implied in our model. We find that our results on $\langle \sigma v \rangle$ are satisfied with and close to the upper limit of IceCube analysis. More data from comic-ray neutrinos could test our model.Comment: 31 pages, 24 figures, 6 tables; Version to appear in JHE