Merlin Reichard (KIAS), "Exploring DM electromagnetic moments with direct detection experiments"

Wednesday May 13, 2026, 3:00 PM → 4:00 PM Asia/Seoul

CTPU Seminar room (Theory Bldg, 4F)

Dark matter (DM) remains one of the major puzzles in modern physics, as its origin and interactions with Standard Model particles are largely unknown. Despite extensive theoretical and experimental efforts, no conclusive non-gravitational signals have been observed so far, motivating the exploration of alternative interaction scenarios. One well-motivated possibility is that DM possesses electromagnetic (EM) interactions. Such couplings allow DM to interact with nuclei or electrons, making direct detection experiments an obvious choice in probing these models.

In this presentation, I focus on the case of spin-1/2 DM and its signatures in direct detection experiments. For small momentum transfer to the target, the interaction with the photon can be parameterized in terms of five independent electromagnetic moments. Using a factorized decomposition of the predicted event rate, I show how the sensitivity of current generation experiments such as XENON1T, PICO-60, and DarkSide-50 can be efficiently estimated. This framework also enables a systematic study of interference effects among the different EM interactions, highlighting the complementarity of experiments with different target materials.

In principle, these EM moments can be generated via quantum loops. After presenting the analytical expressions for the EM moments of a neutral spin-1/2 fermion generated by t-channel mediators at the one-loop level, I will translate the model-independent constraints on the EFT coefficients to the UV model parameter space. As case study I will present the results for the archetypical Majorana DM candidate, the lightest neutralino, whose Majorana nature restricts the number of its EM moments to one: the anapole moment. Finally, I discuss a tau-philic Dirac DM toy model in which quantum loop effects induce a magnetic dipole moment and a charge radius; if parity is violated, an anapole moment is generated, while CP violation further induces an electric dipole moment. Direct detection experiments turn out to provide a powerful probe of the underlying parameter space, allowing the exclusion of DM candidates with masses up to the TeV scale in parts of the parameter space.