We study the B − L gauge extension of the Standard Model which contains a singlet scalar and three right-handed neutrinos. The vacuum expectation value of the singlet scalar breaks the U (1) B−L symmetry.Here the third generation right-handed neutrino is qualified as the dark matter candidate, as an artifact of Z 2 -charge assignment. Relic abundance of the dark matter is consistent with WMAP9 and PLANCK data, only near scalar resonances where dark matter mass is almost half of the scalar boson masses. Requiring correct relic abundance, we restrict the parameter space of the scalar mixing angle and mass of the heavy scalar boson of this model. Besides this, the maximum value of spin-independent scattering cross-section off nucleon is well-below the Xenon100 and recent LUX exclusion limits and can be probed by future Xenon1T experiment. In addition, we compute the annihilation of the dark matter into two photon final state in detail and compare with the Fermi-LAT upper bound on σv γγ for NFW and Einasto profile.

We study the extension of Minimal Supersymmetric Standard Model by adding one singlet and one hypercharge zero SU(2) triplet chiral superfield. The triplet sector gives an additional contributions to the scalar masses and we find that the lightest CP-even Higgs boson can have a mass of 119-120 GeV at the tree level, and radiative correction raises the value to 125 GeV. In this model no significant contributions from stop loops is needed to get the required Higgs mass which alleviates the fine tuning problem of fixing the stop mass to a high precision at the GUT scale. In addition this model gives a neutralino dark matter of mass around 100 GeV which is a mixture of Higgsino and Triplino with a dark matter density consistent with WMAP observations. The spin-independent scattering cross-section with nucleons is 10 −43 cm 2 , which makes it consistent with the bounds from direct detection experiments like XENON100 and others.

Editor: S. Dodelson Keywords:Dark matter phenomenology Gamma-ray excess Gauge extension of SM Recently the study of anomalous gamma-ray emission in the regions surrounding the galactic center has drawn a lot of attention as it points out that the excess of ∼ 1-3 GeV gamma-ray in the low latitude is consistent with the emission expected from annihilating dark matter. The best-fit to the gamma-ray spectrum corresponds to dark matter (DM) candidate having mass in the range ∼ 31-40 GeV annihilating into bb-pair with cross-section σ v = (1.4-2.0) × 10 −26 cm 3 s −1 . We have shown that the Higgs-portal dark matter models in presence of scalar resonance (in the annihilation channel) are well-suited for explaining these phenomena. In addition, the parameter space of these models also satisfies constraints from the LHC Higgs searches, relic abundance and direct detection experiments. We also comment on real singlet scalar Higgs-portal DM model which is found to be incompatible with the recent analysis.

Abstract:We propose an economic extension of minimal supersymmetric standard model with a SU(2) singlet and Y = 0 triplet, which can explain (i) the 125 GeV Higgs boson without fine tuning, (ii) the 130 GeV γ-ray line seen at Fermi-LAT, (as well as a second photon line at 114 GeV)(iii) an enhanced Higgs di-photon decay rate seen by ATLAS, while being consistent with dark matter relic density and recent XENON 100 exclusion limits on spin-independent direct detection cross-section. We obtain the required cross-section of 10 −27 cm 3 s −1 for the 130 GeV γ-ray flux through the resonant annihilation of dark matter via pseudoscalar triplet Higgs of mass ∼260 GeV. The dark matter is predominantly binohiggsino which has large couplings with photons (through higgsino) and gives correct relic density (through bino). We get the enhanced Higgs diphoton decay rate, R γγ ≃ 1.224 dominantly contributed by the light chargino-loops, which can account for the reported excess seen in the h → γγ channel by ATLAS.

We revisit the two real singlet extension of the Standard Model with a $$ {Z}_2\times {Z}_2^{\prime } $$ Z 2 × Z 2 ′ symmetry. One of the singlet scalars S2, by virtue of an unbroken $$ {Z}_2^{\prime } $$ Z 2 ′ symmetry, plays the role of a stable dark matter candidate. The other scalar S1, with spontaneously broken Z2-symmetry, mixes with the SM Higgs boson and acts as the scalar mediator. We analyze the model by putting in the entire set of theoretical and recent experimental constraints. The latest bounds from direct detection Xenon1T experiment severely restricts the allowed region of parameter space of couplings. To ensure the dark matter satisfies the relic abundance criterion, we rely on the Breit-Wigner enhanced annihilation cross-section. Further, we study the viability of explaining the observed gamma-ray excess in the galactic center in this model with a dark matter of mass in the ∼ 36 − 51 GeV window and present our conclusions.