English

Potentially Large One-loop Corrections to WIMP Annihilation

High Energy Physics - Phenomenology 2010-05-25 v2 Cosmology and Nongalactic Astrophysics

Abstract

We compute one-loop corrections to the annihilation of non--relativistic particles χ\chi due to the exchange of a (gauge or Higgs) boson ϕ\phi with mass μ\mu in the initial state. In the limit mχμm_\chi \gg \mu this leads to the "Sommerfeld enhancement" of the annihilation cross section. However, here we are interested in the case μ\lsimmχ\mu \lsim m_\chi, where the one--loop corrections are well--behaved, but can still be sizable. We find simple and accurate expressions for annihilation from both SS- and PP-wave initial states; they differ from each other if μ0\mu \neq 0. In order to apply our results to the calculation of the relic density of Weakly Interacting Massive Particles (WIMPs), we describe how to compute the thermal average of the corrected cross sections. We apply this formalism to scalar and Dirac fermion singlet WIMPs, and show that the corrections are always very small in the former case, but can be very large in the latter. Moreover, in the context of the Minimal Supersymmetric Standard Model, these corrections can decrease the relic density of neutralinos by more than 1%, if the lightest neutralino is a strongly mixed state.

Keywords

Cite

@article{arxiv.0911.3795,
  title  = {Potentially Large One-loop Corrections to WIMP Annihilation},
  author = {M. Drees and J. M. Kim and K. I. Nagao},
  journal= {arXiv preprint arXiv:0911.3795},
  year   = {2010}
}

Comments

25 pages, 8 figures. Added an appendix showing that the approximation works well in a scalar toy model. To be published in PRD.

R2 v1 2026-06-21T14:13:42.088Z