Susceptibilities and in-medium effects in Dark Matter-electron scattering

Research Project, 2023 – 2026

Despite decades of experimental searches, the particles that comprise our universe’s dark matter (DM) have not yet been detected. This could indicate that they are too light to be observed through the nuclear recoils induced by the scattering of DM particles in conventional detectors, and motivates the search for DM in the recoils of a lighter target: the electron. The purpose of this project is to develop, implement and apply a new formalism for the scattering of DM particles by electrons bound in materials. This will be done in four work streams, where the proposed formalism will be 1) developed; 2) implemented numerically; 3) applied to data analysis; and 4) optimised for DM discovery. The novelty of this project lies in the combined use of particle physics and condensed matter theory. The former is used to describe general DM-electron interactions in materials, and the latter to model the material response in terms of generalised susceptibilities. An important feature of the proposed formalism is that it automatically accounts for crucial in-medium effects, such as screening and collective excitations. When completed, the new formalism will therefore be a very powerful tool in the analysis of data from DM experiments that search for electronic transitions in crystals or superconductors, where in-medium effects are of great importance. Ultimately, this project will answer the fundamental question of how detector materials respond to general DM-electron interactions.