Abstract
By including spectator fields into the Boltzmann equations for Leptogenesis, we show that partially equilibrated spectator interactions can have a significant impact on the freeze-out value of the asymmetry in the strong washout regime. The final asymmetry is typically increased, since partially equilibrated spectators ''hide'' a part of the asymmetry from washout. We study examples with leptonic and non-leptonic spectator processes, assuming thermal initial conditions, and find up to 50% enhanced asymmetries compared to the limit of fully equilibrated spectators. Together with a comprehensive overview of the equilibration temperatures for various Standard Model processes, the numerical results indicate the ranges when the limiting cases of either fully equilibrated or negligible spectator fields are applicable and when they are not. Our findings also indicate an increased sensitivity to initial conditions and finite density corrections even in the strong washout regime.
Highlights
For the two examples (τ -Yukawa equilibration and b-Yukawa together with strongsphaleron equilibration) worked out numerically in sections 4 and 5, the freeze-out asymmetry assuming full equilibration of the spectator fields is larger than when these effects are neglected, in consistency with the well-known results presented in refs. [2, 3]
We find that the freeze-out asymmetry can be enhanced compared to the two limiting cases, cf. figures 3–5
The enhancement is typically more pronounced the stronger the washout strength is. This is because during the early stages of Leptogenesis, the large asymmetries that are present can be partly transferred to spectator fields
Summary
Closely track the asymmetry in left-handed leptons, that experiences direct washout). This is of interest, as one should expect here the largest effect from the partial equilibration on the freeze-out asymmetry, as part of the asymmetry (in principle up to one third) is hidden from washout in the right-handed τ -leptons.
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