Abstract
The Affleck-Dine leptogenesis scenario along the LHu flat direction is reconsidered. It is known that successful Affleck-Dine leptogenesis requires that the lightest neutrino mass is extremely small. This situation can be significantly relaxed if the neutrino mass in the early universe is different from the present one. We consider a supersymmetric Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) type model, which provides a solution to the strong CP problem and generates a SUSY μ-term and right-handed neutrino masses. If the PQ scale during lepton number generation is much larger than the present value, leptogenesis is very efficient so that enough baryon number can be generated without introducing a hierarchically small neutrino mass. The final baryon asymmetry is related to the μ-term, and hence linked to the level of electroweak fine-tuning. We also show the PQ breaking scalar dynamics that keeps a large PQ breaking scale during inflation and lepton number generation. The μ-term generating superpotential plays an important role for preserving the lepton asymmetry during saxion oscillation. In this scenario, the axion isocurvature perturbation is naturally suppressed.
Highlights
If the RHN mass is generated by the PQ field, it naturally takes hierarchically different values between the early universe and the present epoch
The PQ scalar can be stabilized at the Planck scale in the early universe until the lepton asymmetry is generated, which makes leptogenesis much more efficient than in the ordinary scenario
The predicted lightest neutrino mass to reproduce the observed baryon asymmetry can be close to the neutrino mass differences known from the neutrino oscillation data
Summary
We consider the neutrino sector for AD leptogenesis and the PQ breaking sector, which are described by the following superpotential,. The neutrino mass is generated by the see-saw mechanism at low energy X ∼ f : mν. And in the following, we assume that the lepton asymmetry is generated along the flattest LHu direction, which corresponds to the smallest neutrino mass mν. Since the phase minimum of this Hubble-induced A term differs from the soft SUSY breaking-induced A term, the AD field obtains angular momentum in the complex plane, generating the lepton number. Note that we have one more phase direction orthogonal to the above massive direction This does not appear in the potential, so is a massless mode corresponding to the axion of the spontaneously broken PQ symmetry. In the limit of φ0 X0, the massive mode is mostly aφ-like and the massless mode is mostly aX -like
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