Dark Higgs channel for Fermi GeV γ-ray excess

P Ko,Yong Tang

doi:10.1088/1475-7516/2016/02/011

Abstract

Dark Higgs is very generic in dark matter models where DM is stabilized by some spontaneously broken dark gauge symmetries. Motivated by tentative GeV scale γ-ray excess from the galactic center (GC), we investigate a scenario where a pair of dark matter X annihilates into a pair of dark Higgs H2, which subsequently decays into standard model particles through its mixing with SM Higgs boson. Besides the two-body decay of H2, we also include multibody decay channels of the dark Higgs. We find that the best-fit point is around MX ≃ 95.0 GeV, MH2 ≃ 86.7 GeV, ⟨σ v⟩ ≃ 4.0 × 10−26cm3/s and gives a p-value ≃ 0.40. Implication of this result is described in the context of dark matter models with dark gauge symmetries. Since such a dark Higgs boson is very difficult to produce at colliders, indirect DM detections of cosmic γ-rays could be an important probe of dark sectors, complementary to collider searches.

Highlights

Dark Higgs is very generic in dark matter models where DM is stabilized by some spontaneously broken dark gauge symmetries
Discussions has been extended to cascade two-body decay through new mediators, such as Z and dark Higgs H2, which are ubiquitous in new physics beyond SM
This work is intended to investigate GeV scale gamma-ray excess in models where DM annihilates into a pair of heavy dark Higgs (> 1GeV) which subsequently could decay into multi-body final states such as W W ∗ or W ∗W ∗, where W ∗ is a virtual W boson

Summary

FORMALISM

X + X → H2 + H2, followed by H2 → SM + SM (+SM ). An interesting thing is that MX MH2 125GeV give a good-fit This point is equivalent to the channel that DM X annihilates into SM Higgs, which has been already found in previous study [50, 55]. All the best-fit points give χ2 ∼ 44, and the minimal χ2 is reached when MX 87.0GeV, MH2 82.1GeV and σv 4.7 × 10−26cm3/s with χ2min/d.o.f 42.6/(22 − 3) which corresponds to a p-value, 1.5 × 10−3. It seems that this is not a good fit. We can see that the favored regions are consistent with those in Figs. 3 and 4 within 2-3σ

RELIC ABUNDANCE AND PHENOMENOLOGY

SUMMARY