Leptogenesis via Collisions: Leaking Lepton Number to the Hidden Sector

We propose a lepto-baryogenesis mechanism in which the non-zero B-L of the universe is produced in out-of-equilibrium, lepton number and CP violating scattering processes that convert ordinary particles into particles of some hidden sector. In particular, we consider the processes $l \phi > l’ \phi’, \bar l’ \bar phi’$mediatedbytheheavyMajorananeutrinos$N$ of the seesaw mechanism, where $l$ and $\varphi$ are ordinary lepton and Higgs doublets and $l^{\mathrm{\prime }}$, ${\varphi }^{\mathrm{\prime }}$ their hidden counterparts. Such a leptogenesis mechanism is effective even if the reheating temperature is much smaller than the heavy neutrino masses. In particular, it can be as low as ${10}^9$ GeV.