Probing scalar, Dirac, Majorana and vector DM through spin-0 electron-specific mediator at the electron fixed-target experiments

We discuss the thermal target curves of Majorana, Dirac, scalar and vector light dark matter (DM) that are associated with the freeze-out mechanism via the annihilation into e^+e^- pair through the electron-specific spin-0 mediator of dark matter. We also discuss the mechanism to produce the regarding DM mediator in the electron (positron) fixed-target experiments such as NA64e and LDMX. We derive the corresponding experimental reaches of the NA64e and LDMX that are complementary to the DM thermal target parameter space.