Non-perturbative effect on thermal relic abundance of dark matter

We point out that thermal relic abundance of the dark matter is strongly altered by a non-perturbative effect called the Sommerfeld enhancement, when constituent particles of the dark matter are non-singlet under the SU(2)(L) gauge interaction and much heavier than the weak gauge bosons. Typical candidates for such dark matter particles are the heavy wino- and higgsino-like neutralinos. We investigate the non-perturbative effect on the relic abundance of dark matter for the wino-like neutralino as an example. We show that its thermal abundance is reduced by 50% compared to the perturbative result. The wino-like neutralino mass consistent with the observed dark matter abundance turns out to be 2.7 TeV <= m <= 3.0 TeV. (c) 2007 Elsevier B.V. All rights reserved.