The 130 GeV gamma-ray line and Sommerfeld enhancements

Understand

Recently, possible indications of line spectral features in the Fermi-LAT photon spectrum towards the galactic center have been reported.

• If the distinct line features arise from dark matter (DM) annihilation into $\gamma X (X=\gamma, Z^{0} or h^{0})$, the corresponding annihilation cross-section is unnaturally large for typical loop-induced radiative processes.
• On the other hand, it is still too small to be responsible for the observed DM relic density.
• We show that the mechanism of Sommerfeld enhancement with scalar force-carrier can provide a simple solution to these puzzles.