Thermal and non-thermal production of dark matter via Z′-portal(s)

We study the genesis of dark matter in the primordial Universe for representative classes of Z'-portals models. For weak-scale Z' mediators we compute the range of values of the kinetic mixing allowed by WMAP/PLANCK experiments corresponding to a FIMP regime. We show that very small values of delta (10(-12) less than or similar to delta less than or similar to 10(-11)) are sufficient to produce the right amount of dark matter. We also analyse the case of very massive gauge mediators, whose mass m(Z'), is larger than the reheating temperature, T-RH, with a weak-scale coupling g(D) to ordinary matter. Relic abundance constraints then impose a direct correlation between T-RH and the effective scale A of the interactions: Lambda similar to 10(3) - 10(5) x T-RH. Finally we describe in some detail the process of dark thermalisation and study its consequences on the computation of the relic abundance.