Nonthermal Solar Stalling of an Inelastic Scalar Signal in Xenon

Abstract

The LUX-ZEPLIN experiment has reported one nuclear-recoil candidate at $248\kev$ in an extended-energy search. We construct an anomaly-free $U(1)_{B-3L_\tau}$ model in which an $840\gev$ complex scalar undergoes an endothermic transition with splitting $320\kev$. A $160\mev$ vector with dark charge $Q_\chi=1$ gives $0.958$ accepted events in a public LZ-response reconstruction while scalar annihilation yields $\Omega h^2=0.1200$. The physical nucleon ratio $f_n/f_p=-0.86985$ suppresses solar iron capture, leaving $C_\odot=1.09\times10^{19}\,{\rm s}^{-1}$. We then evolve captured particles in energy, angular momentum, and internal state, including finite collision rates, thermal nuclear velocities, and the excited-state decay. The distribution stalls at an equivalent radius $r_{\rm eff}=0.194$--$0.198\rsun$, for which $\Gamma_{\rm ann}=(1.33$--$1.38)\times10^{15}\,{\rm s}^{-1}$, below a model-specific IceCube public-data proxy by more than three orders of magnitude. The benchmark also lies below the dedicated NA64 $B-L$ limit. Thus solar-neutrino bounds on electroweak inelastic dark matter do not transfer model-independently to light-mediator scalar realizations.