Who: Achim Schwenk, TU Darmstadt
Place: Hybrid Seminar: Donostia International Physics Center
Date: Wednesday, 27 July 2022, 12:00
We discuss the application of chiral effective field theory (EFT) to the calculation of nuclear responses for the scattering of weakly interacting massive particles (WIMPs) off nuclear targets. A consistent interpretation of the limits set by current and future direct-detection searches in terms of the WIMP parameter space requires the use of a series of EFTs to bridge the gap between the scales of physics beyond the standard model and the nuclear scales to which the experimental searches are sensitive. Chiral EFT incorporates the QCD constraints in the nucleon matrix elements and the nuclear responses, and thus provides the necessary formalism to describe the hadronic and nuclear aspects of direct detection experiments.
We review the current status of calculations for WIMP interactions with nuclei based in chiral EFT. This includes large-scale calculations for spin-dependent WIMP scattering for all nuclei relevant for dark matter direct detection. For spin-dependent interactions, the inclusion of WIMPs coupling to two nucleons through two-body currents has especially improved the sensitivity of experiments to the paired species, e.g., for the spin-dependent WIMP- proton cross section limits for xenon detectors. Moreover, we have developed a general framework for WIMPs coupling to nuclei, focusing on all leading spin-independent nuclear responses that can be coherently enhanced with the number of nucleons. In fact, after the standard spin- independent WIMP-nucleon interactions, the next largest response results from the coupling of WIMPs to pions in nuclei. This led to the first limits for the WIMP-pion coupling from the XENON1T experiment. We also discuss insights provided by chiral EFT for the analysis of the experiments and connections of the nuclear responses to coherent elastic neutrino-nucleus scattering.
Host: J. J. Gomez-Cadenas