The 248 keV LZ Recoil: A Possible Hint of Non-SM-Like Quark Yukawa Couplings with a Scalar-Portal Dark Matter

The recent observation of an isolated nuclear recoil event at an energy of $248\pm 23(stat)\pm 23(sys)$ keV, as reported by the LUX-ZEPLIN (LZ) collaboration, can be an intriguing signature for Beyond the Standard Model (BSM) possibilities, particularly for dark matter (DM). This paper explores a scenario in which the observed recoil could simultaneously signal inelastic DM and a flavor-specific New Physics (NP) interaction in the quark sector. Considering a minimal extension of the Standard Model (SM) with two closely degenerate $Z_2$-odd vector-like fermions (VLFs), interacting with the SM via a scalar portal, the analysis shows that a perfect agreement with the observed 248 keV nuclear recoil can be achieved if the quark Yukawa couplings are allowed to deviate from their SM values. The underlying quarkophilic NP can originate from a dimension-6 effective operator at a NP scale $\mathrm{\Lambda }\le \mathcal{O}(10)$ TeV. Future collider searches can be crucial to test/falsify the proposal.