= Heavy-boson decay baryogenesis
{title2=$\epsilon=(r-\bar r)/2$}
Consider equal initial abundances of a heavy <boson> $X$ and its <antiparticle>. Two decay channels with different <baryon numbers>, for example $X\to uu$ and $X\to\bar d e^+$, have <branching fractions> $r$ and $1-r$. The conjugate channels have <branching fractions> $\bar r$ and $1-\bar r$. Their mean <baryon numbers> are $r-1/3$ and $-\bar r+1/3$, so each particle-antiparticle pair produces $r-\bar r$, or $\epsilon$ per decaying particle. Unequal <branching fractions> require <CP violation>; equal total <decay widths> are consistent with <CPT symmetry>. <Baryon number> cannot be assigned so that both channels conserve it. An initial abundance decaying outside <thermal equilibrium>, after inverse production becomes ineffective, can therefore generate a nonzero <baryon asymmetry>. At the microscopic level a decay-rate difference caused by <CP violation> requires interference of <decay amplitudes> with both a relative <weak phase> and an <absorptive phase>; complex couplings alone do not guarantee it. Subsequent <baryon-number washout> must be ineffective for the produced asymmetry to survive.
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