Atomic responses function to study dark matter-electron interactions

Mukesh Kumar Pandey^1*, Chih-Pan Wu², Lakhwinder Singh⁴, C. P. Liu², Jiunn-Wei Chen¹, Hsin-Chang Chi², Henry T. Wong³

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Department of Physics, National Dong Hwa University, Hualien, Taiwan
³Institute of Physics, Academia Sinica, Taipei, Taiwan
⁴Department of Physics, Central University of South Bihar, Gaya, India

* Presenter:Mukesh Kumar Pandey, email:mkpandey@gmail.com

In this work, we focus on calculating the atomic response function (ARF) for target such as Germanium and Xenon, which are widely used in dark matter (DM) search experiments. These calculations are especially valuable for exploring interactions between dark matter particles and electrons. Through this study, we find that the probability or rate at which atoms can become ionized through DM-electron scattering can generally be described using four independent atomic response functions. Our goal is to provide a detailed atomic response function for DM-atom scattering at the leading order (LO) level, utilizing advanced and well-benchmarked atomic many-body calculations.
Our findings reveal that these newly identified atomic responses play a significant role in various scenarios, especially in the context of light-dark matter (LDM) particle interactions with atomic electrons, which we analyze using effective field theory. Using the calculated atomic response functions, we establish exclusion limits with a 90% confidence level (C.L.) on the strength of multiple DM-electron interactions, based on the null results of current DM search experiments with Germanium and Xenon as target.
Our approach applies robust methods like the relativistic random-phase approximation (RRPA) and the relativistic frozen-core approximation (RFCA) to obtain differential cross sections with high accuracy—within a 5% margin for RRPA and a 20% margin for RFCA. These findings, which provide a more detailed understanding of DM-atom interactions, will be presented at an upcoming conference.
This research was funded by the National Science and Technology Council (NSTC) of Taiwan, supporting our ongoing contributions to dark matter research.

Keywords: Atomic response function (ARF), Spin-Dependent(SD) Dark matter, Spin-independent(SI) Dark Matter, Germanium and Xenon detectors, Nonrelativistic effective field theory