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

TL;DR

This paper investigates gamma-ray line signals from a non-abelian spin-1 dark matter model, highlighting enhanced annihilation cross sections and new modes, with implications for detection via gamma-ray telescopes.

Contribution

It introduces a spin-1 dark matter model with larger annihilation cross sections and novel gamma-ray signatures compared to fermionic models like Wino DM.

Findings

Enhanced annihilation cross sections into gamma-ray lines compared to Wino DM.

Prediction of a new annihilation mode into Z' gamma involving heavy vector bosons.

Potential to probe DM masses up to 25.3 TeV with CTA observations.

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, $Z' \gamma$. 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.