WIMP-nucleus scattering in chiral effective theory

TL;DR

This paper analyzes long-distance QCD effects on WIMP-nucleus interactions using chiral effective theory, revealing significant corrections to cross-sections and recoil spectra, especially in isospin-violating regimes.

Contribution

It provides the first comprehensive calculation of next-to-leading-order corrections to WIMP-nucleus scattering within chiral effective theory, including two-nucleon effects and form factor shifts.

Findings

Corrections significantly alter scattering rates in certain parameter regions.

The simple two-parameter model for scalar interactions is insufficient.

Recoil spectra shapes are qualitatively changed by the new effects.

Abstract

We discuss long-distance QCD corrections to the WIMP-nucleon(s) interactions in the framework of chiral effective theory. For scalar-mediated WIMP-quark interactions, we calculate all the next-to-leading-order corrections to the WIMP-nucleus elastic cross-section, including two-nucleon amplitudes and recoil-energy dependent shifts to the single-nucleon scalar form factors. As a consequence, the scalar-mediated WIMP-nucleus cross-section cannot be parameterized in terms of just two quantities, namely the neutron and proton scalar form factors at zero momentum transfer, but additional parameters appear, depending on the short-distance WIMP-quark interaction. Moreover, multiplicative factorization of the cross-section into particle, nuclear and astro-particle parts is violated. In practice, while the new effects are of the natural size expected by chiral power counting, they become very important in those regions of parameter space where the leading order WIMP-nucleus amplitude is suppressed, including the so-called "isospin-violating dark matter" regime. In these regions of parameter space we find order-of-magnitude corrections to the total scattering rates and qualitative changes to the shape of recoil spectra.