We update indirect constraints on Electro-Weak Dark Matter (EWDM) considering
the Sommerfeld-Ramsauer-Townsend (SRT) effect for its annihilations into a pair
of standard model gauge bosons assuming that EWDM accounts for the observed
dark matter (DM) relic density for a given DM mass and mass gaps among the
multiplet components. For the radiative or smaller mass splitting, the
hypercharged triplet and higher multiplet EWDMs are ruled out up to the DM mass
~ 10 - 20 TeV by the combination of the most recent data from AMS-02
(antiproton), Fermi-LAT (gamma-ray), and HESS (gamma-line). The Majorana
triplet (wino-like) EWDM can evade all the indirect constraints only around
Ramsauer-Townsend dips which can occur for a tiny mass splitting of order 10
MeV or less. In the case of the doublet (Higgsino-like) EWDM, a wide range of
its mass > 500 GeV is allowed except Sommerfeld peak regions. Such a stringent
limit on the triplet DM can be evaded by employing a larger mass gap of the
order of 10 GeV which allows its mass larger than about 1 TeV. However, the
future CTA experiment will be able to cover most of the unconstrained parameter
space.Comment: 17 pages, 4 figures; result for an O(10 GeV) mass gap, future
sensitivity of CTA, and references adde
