Effect of inelastic scalar dark matter in hidden $U(1)$ scenario after the LZ nuclear recoil

Abstract

We study a hidden $U(1)_H$ extension of the Standard Model (SM) introducing two SM singlet complex scalar fields where one of them can be considered as a viable inelastic Dark Matter (DM) candidate due to its $U(1)_H$ charge being half of the charge of the other one which develops a vacuum expectation value. First we estimate a parameter region satisfying observed DM relic abundance through DM annihilation and further use these parameters to study inelastic DM-nucleus scattering to reproduce the recent high nuclear recoil energy event found by LZ collaboration. These interactions are mediated by a dark photon $(A^\prime)$ which is evolved after the spontaneous breaking of $U(1)_H$ symmetry and having a kinetic mixing with the SM photon. Hence we estimate bounds on the kinetic mixing as a function of $A^\prime$ mass and finally compare it with existing experimental bounds from different beam-dump and collider experiments. These parameters could be probed by lifetime and energy frontier experiments in future.