Resummed Photon Spectra for WIMP Annihilation

TL;DR

This paper develops an effective field theory framework combining SCET techniques to accurately predict the photon spectrum from heavy WIMP annihilation, improving the interpretation of gamma-ray line searches in dark matter detection.

Contribution

It introduces a novel EFT approach that incorporates multiple SCET modes and resummation techniques, unifying previous approximations for WIMP photon spectra.

Findings

Numerically significant corrections to previous predictions.

Enhanced precision in photon spectrum modeling for indirect detection.

Demonstrates the importance of including spectrum details in experimental analysis.

Abstract

We construct an effective field theory (EFT) description of the hard photon spectrum for heavy WIMP annihilation. This facilitates precision predictions relevant for line searches, and allows the incorporation of non-trivial energy resolution effects. Our framework combines techniques from non-relativistic EFTs and soft-collinear effective theory (SCET), as well as its multi-scale extensions that have been recently introduced for studying jet substructure. We find a number of interesting features, including the simultaneous presence of SCET$_{\text{I}}$ and SCET$_{\text{II}}$ modes, as well as collinear-soft modes at the electroweak scale. We derive a factorization formula that enables both the resummation of the leading large Sudakov double logarithms that appear in the perturbative spectrum, and the inclusion of Sommerfeld enhancement effects. Consistency of this factorization is demonstrated to leading logarithmic order through explicit calculation. Our final result contains both the exclusive and the inclusive limits, thereby providing a unifying description of these two previously-considered approximations. We estimate the impact on experimental sensitivity, focusing for concreteness on an SU(2)$_{W}$ triplet fermion dark matter - the pure wino - where the strongest constraints are due to a search for gamma-ray lines from the Galactic Center. We find numerically significant corrections compared to previous results, thereby highlighting the importance of accounting for the photon spectrum when interpreting data from current and future indirect detection experiments.