Leptogenesis, Z' bosons, and the reheating temperature of the Universe

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We study the impact for leptogenesis of new U(1) gauge bosons coupled to the heavy Majorana neutrinos.

• They can significantly enhance the efficiency of thermal scenarios in the weak washout regime as long as the Z' masses are not much larger than the reheating temperature ($M_{Z'}<10 T_{rh}$), with the highest efficiencies obtained for Z' bosons considerably heavier than the heavy neutrinos ($M_{Z'} > 100 M_1$).
• We show how the allowed region of the parameter space is modified in the presence of a Z' and we also obtain the minimum reheating temperature that is required for these models to be successful.