Galactic Center gamma ray excess from two Higgs doublet portal dark matter

We consider a simple extension of the type-II two-Higgs-doublet model by introducing a real scalar as a candidate for dark matter in the present Universe. The main annihilation mode of the dark matter particle with a mass of around 31–40 GeV is into a $b\overline{b}$ pair, and this annihilation mode suitably explains the observed excess of the gamma-ray flux from the Galactic Center. We identify the parameter region of the model that can fit the gamma-ray excess and satisfy phenomenological constraints, such as the observed dark matter relic density and the null results of direct dark matter search experiments. Most of the parameter region is found to be within the search reach of future direct dark matter detection experiments.

Figure 1

Contours of the invisible decay branching ratio of the SM-like Higgs boson, $\mathrm{BR}(h\to \varphi \varphi )=0.1$, 0.3, and 0.5. We have taken the DM mass $m_{\varphi }=40\mathrm{GeV}$ and $\tan \beta =10$.

Figure 2

Contours of $\mathrm{\Omega }{h}^2=0.1$ (thick blue line) and $(\sigma v{)}_0$ in units of $10^{-26}{\mathrm{cm}}^3/\mathrm{s}$ (dashed lines) for $m_{\mathrm{DM}}=40\mathrm{GeV}$ and ${\sigma }_2=0.02$. $\tan \beta$ is taken to be 30, 40, and 50 from left to right. The shaded regions are excluded by the LUX (2014) experiment [54], and the expected future sensitivity ($3\times 10^{-47}{\mathrm{cm}}^2$) of the XENON1T experiment [55] is depicted by the thin lines.

Figure 3

Same as Fig. 2 but for $m_{\mathrm{DM}}=30\mathrm{GeV}$.

Figure 4

Same as Fig. 2 but for ${\sigma }_2=0$. $\tan \beta$ is taken to be 10, 20, and 30 from left to right.

Figure 5

Same as Fig. 2 but for $\tan \beta =30$ and ${\sigma }_2=0.01$.