Soft Collinear Effective Theory for Heavy WIMP Annihilation

TL;DR

This paper develops an effective field theory approach to systematically resum large Sudakov logarithms and account for long-distance effects in heavy WIMP annihilation, improving the accuracy of cross section predictions.

Contribution

It introduces a novel EFT framework that disentangles short- and long-distance effects, enabling precise calculations of WIMP annihilation with resummed logarithms and Sommerfeld enhancement.

Findings

Resummed cross section is reduced by a factor of ~3 at 3 TeV mass.

Universal Sudakov logarithms significantly affect annihilation rates.

Effective field theory accurately separates short- and long-distance effects.

Abstract

In a large class of models for Weakly Interacting Massive Particles (WIMPs), the WIMP mass $M$ lies far above the weak scale $m_W$. This work identifies universal Sudakov-type logarithms $\sim \alpha \log^2 (2\,M/m_W)$ that spoil the naive convergence of perturbation theory for annihilation processes. An effective field theory (EFT) framework is presented, allowing the systematic resummation of these logarithms. Another impact of the large separation of scales is that a long-distance wave-function distortion from electroweak boson exchange leads to observable modifications of the cross section. Careful accounting of momentum regions in the EFT allows the rigorously disentanglement of this so-called Sommerfeld enhancement from the short distance hard annihilation process. The WIMP is modeled as a heavy-particle field, while the light, energetic, final-state electroweak gauge bosons are treated as soft and collinear fields. Hard matching coefficients are computed at renormalization scale $\mu \sim 2\,M$, then evolved down to $\mu \sim m_W$, where electroweak symmetry breaking is incorporated and the matching onto the relevant quantum mechanical Hamiltonian is performed. The example of an $SU(2)_W$ triplet scalar dark matter candidate annihilating to line photons is used for concreteness, allowing the numerical exploration of the impact of next-to-leading order corrections and log resummation. For $M \simeq 3$ TeV, the resummed Sommerfeld enhanced cross section is reduced by a factor of $\sim 3$ with respect to the tree-level fixed order result.