Flavored dark matter and the Galactic Center gamma-ray excess

Thermal relic dark matter particles with a mass of 31–40 GeV that dominantly annihilate to bottom quarks have been shown to provide an excellent description of the excess gamma rays observed from the center of the Milky Way. Flavored dark matter provides a well-motivated framework in which the dark matter can dominantly couple to bottom quarks in a flavor-safe manner. We propose a phenomenologically viable model of bottom flavored dark matter that can account for the spectral shape and normalization of the gamma-ray excess while naturally suppressing the elastic scattering cross sections probed by direct detection experiments. This model will be definitively tested with increased exposure at LUX and with data from the upcoming high-energy run of the Large Hadron Collider (LHC).

Figure 1

Feynman diagrams contributing to direct detection.

Figure 2

The $m_{\varphi }-{\lambda }_b$ parameter space of the $b$-FDM model for $m_{{\chi }_b}=40\mathrm{GeV}$. We represent parameters predicting an annihilation cross section consistent with the observed Galactic Center gamma-ray excess (red) and a thermal relic value, $\sigma v=4.4\times 10^{-26}{\mathrm{cm}}^3/\mathrm{s}$ (orange). We also display the limit reported by the LUX Collaboration (brown) assuming a local dark matter density of $0.3\pm 0.1\mathrm{GeV}/{\mathrm{cm}}^3$ [45]. LHC sbottom searches constrain $m_{\varphi }>725\mathrm{GeV}$ (grey). A projection in the mono-$b$ channel with 8 TeV data is also displayed (blue).

Figure 3

The cancellation between the box and photon loop diagrams shown in Fig. 1, compared to the (90% C.L.) upper limits from LUX. Results are shown for $m_{{\chi }_b}=40\mathrm{GeV}$, $m_{{\chi }_d}=60\mathrm{GeV}$, $m_{\varphi }=725\mathrm{GeV}$, and ${\lambda }_b=2.16$.