Sommerfeld Enhancement from Quantum Forces for Dark Matter

TL;DR

This paper investigates how quantum forces influence the Sommerfeld enhancement of dark matter annihilation, revealing novel effects like temperature-induced resonances and background-dependent cross section modifications relevant for cosmology and detection.

Contribution

It provides the first calculation of Sommerfeld factors induced by quantum forces for both bosonic and fermionic mediators, including background effects, with implications for dark matter phenomenology.

Findings

Quantum forces cause temperature-induced resonance peaks.

Background corrections can enhance or suppress annihilation cross sections.

New features differ from traditional Yukawa potential predictions.

Abstract

Quantum forces are long-range interactions that arise only at the loop level. In this work, we study the Sommerfeld enhancement of dark matter (DM) annihilation cross sections caused by quantum forces. One notable feature of quantum forces is that they are subject to coherent enhancement in the presence of a background of mediator particles, which occurs in many situations in cosmology. We show that this effect has important implications for the Sommerfeld enhancement and DM physics. For the first time, we calculate the Sommerfeld factor induced by quantum forces for both bosonic and fermionic mediators, including the background corrections. We observe several novel features of the Sommerfeld factor that do not exist in the case of the Yukawa potential, such as temperature-induced resonance peaks for massless mediators, and having both enhancement and suppression effects in the same model with different DM masses. As direct applications, we discuss the DM phenomenology affected by the Sommerfeld enhancement from quantum forces, including thermal freeze-out, CMB spectral distortion from DM annihilation, and DM indirect detection. We highlight one particularly interesting effect relevant to indirect detection caused by the Sommerfeld enhancement in a non-thermal background of bosonic mediators in the galaxy, in which case the DM mass is shifted due to the background correction and the effective cross section for DM annihilation can be either enhanced or suppressed. This may be important for DM searches in the Milky Way or its satellite galaxies.