Inelastic Dark Matter from a Higher-Dimensional Operator: The LUX-ZEPLIN High-Recoil Event and Thermal Relic

The recent LUX-ZEPLIN (LZ) data shows a nuclear-recoil event around $248\mathrm{k}\mathrm{e}\mathrm{V}$, motivating scenarios in which dark matter (DM) preferentially scatters at large recoil energies. We investigate an inelastic scattering interpretation in terms of a simple extension with a fermionic DM field interacting with the Standard Model through a single dimension-6 operator. A tiny soft symmetry breaking term facilitates an endothermic transition while naturally suppressing elastic scatterings. Without any fine tuning, a simultaneous explanation of the LZ data and the observed relic density can be effected for a DM mass in the $\sim (0.2,1)$ TeV range.