Mixed leptogenesis sources and low-energy neutrino portals

Abstract

A mixed leptogenesis source and its low-energy neutrino portal depend on the same heavy-particle amplitudes. We determine how this common origin restricts matching cancellations and the scalar population produced during reheating. For two Majorana mass levels, each containing a degenerate pair, the inclusive lepton-number-violating invariant fixes an allowed norm domain for the mixed dimension-five coefficient at specified threshold strengths. An aligned flavour texture makes the conventional source vanish as a matrix and gives equal coupling norms for the two massive neutrinos. A continuous family preserves the neutrino-mass fit while relating the source to unequal light coupling strengths. The matched couplings give benchmark vacuum lifetimes of $1.62\times10^{12}\,\mathrm{s}$ and $2.80\times10^{11}\,\mathrm{s}$, while reheating normalized to the baryon abundance determines the primary spectrum. In the massless Born approximation with dilute outgoing states, bath-produced scalars carry $4.81\times10^{-5}$ of the primary scalar energy but contribute $11.1$ times its variance. The positive production functional converts the matching constraint into a conditional variance bound. We derive the scalar-mass dependence of stimulated emission and the Hartree moment equation, keeping the scalar mass and quartic as renormalized matching inputs. These results link the leptogenesis source to light-neutrino decay and the finite-density quantities entering subsequent coupled transport.