Gamma-ray line from electroweakly interacting non-abelian spin-1 dark matter

Abstract

We study gamma-ray line signatures from electroweakly interacting non-abelian spin-1 dark matter (DM). In this model, $Z_2$-odd spin-1 particles including a DM candidate have the SU(2)${}_L$ triplet-like features, and the Sommerfeld enhancement is relevant in the annihilation processes. We derive the annihilation cross sections contributing to the photon emission and compare with the SU(2)${}_L$ triplet fermions, such as Wino DM in the supersymmetric Standard Model. The Sommerfeld enhancement factor is approximately the same in both systems, while our spin-1 DM predicts the larger annihilation cross sections into $\gamma \gamma /Z\gamma$ modes than those of the Wino by $\frac{38}{9}$. This is because a spin-1 DM pair forms not only $J=0$ but also $J=2$ partial wave states where $J$ denotes the total spin angular momentum. Our spin-1 DM also has a new annihilation mode into $Z_2$-even extra heavy vector and photon, $Z^{\prime }\gamma$. For this mode, the photon energy depends on the masses of DM and the heavy vector, and thus we have a chance to probe the mass spectrum. The latest gamma-ray line search in the Galactic Center region gives a strong constraint on our spin-$1$ DM. We can probe the DM mass for $\lesssim 25.3$TeV by the Cherenkov Telescope Array experiment even if we assume a conservative DM density profile.

31 pages, 6 figures, 2 tables, the version published in JHEP

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