Constraints on light dark matter effective operators from the LUX-ZEPLIN experiment

Abstract Light sub-GeV dark matter (DM) particles up-scattered by high-energy cosmic rays (CRs) (referred to as CRDM) can be energetic and become detectable by conventional DM direct detection experiments. Nevertheless, current CRDM theoretical frameworks remain limited by model-dependent parameterizations, whereas the effective operators provides a model-independent computing framework. In this work, we systematically investigate the general relativistic DM-nucleus spin-independent interactions. We first construct effective operators for dark matter with spin up to two, i.e. spin-1/2 fermionic DM ( χ ), the scalar DM ( ϕ ), the vector DM ( V μ ), spin-3/2 fermionic DM (Ψ) and spin-2 DM ( T μν ). We then derive the CRDM flux and the nuclear recoil event rate based on these operators, and employ nuclear recoil data from the LUX-ZEPLIN (LZ) experiment to constrain all effective operators. We set stringent constraints on the CRDM-nucleon scattering cross section for sub-GeV DM. Especially, our results show that the exclusion limits from the spin-2 T μν operator differ by as much as ten orders of magnitude from those calculated using constant cross section.