Interpreting the LZ 248 keV Event using Dark QCD

Abstract

The LUX-ZEPLIN (LZ) Collaboration has reported a nuclear-recoil candidate with reconstructed energy $248\pm 23_{\mathrm{stat}}\pm 23_{\mathrm{sys}}\mathrm{keV}$. We investigate an interpretation in terms of composite inelastic dark matter, in which a dimension-ten operator splits the lightest baryon of a confining $SU(3{)}_{\mathrm{D}}$ theory into two Majorana states. Endothermic scattering is mediated by a leptophobic vector coupled to baryon number. For a dark-baryon mass of $1\mathrm{TeV}$ and a splitting of $300\mathrm{keV}$, a reference nucleon cross section of $6.5\times 10^{-43}\mathrm{c}{\mathrm{m}}^2$ lies within LZ's published two-sided 90\% confidence interval. This benchmark fixes $M_V/g_B\simeq 9.9\mathrm{TeV}$, where $M_V$ and $g_B$ are the mediator mass and baryon-number gauge coupling, and is compatible with solar neutrino and dijet constraints.

6 pages, 1 figure