Reheating and Supersymmetric Flat-Direction Baryogenesis

TL;DR

The paper investigates Affleck-Dine baryogenesis in the MSSM under realistic reheating scenarios, showing that superpotential couplings connect flat directions to fields that can be produced in inflaton decays. The resultant thermal plasma induces masses $h^2T^2$ and thermal $A$-terms, driving earlier oscillations ($H_{ ext{osc}} eq m_{3/2}$) and potentially evaporating the flat-direction condensate, which can substantially alter the predicted baryon asymmetry $n_B/s$. By scanning over GUT- and Planck-scale lifting operators (dimension $n$), Yukawa couplings $h$, gauge couplings $g$, and the reheat scale, the authors map when thermal effects trigger oscillations and whether evaporation occurs before condensate domination. They find that, for most MSSM flat directions with $h o 10^{-2}$, the generated asymmetry is typically small or diluted, while certain exceptional directions with smaller $h$ or larger $M$ can yield larger $n_B/s$ or influence Q-ball formation; overall, reheating and finite-temperature dynamics tightly constrain viable baryogenesis scenarios in the MSSM.

Abstract

We re-examine Affleck-Dine baryo/leptogenesis from the oscillation of condensates along flat directions of the supersymmetric standard model, which attained large vevs at the end of inflationary epoque. The key observation is that superpotential interactions couple the flat directions to other fields, which acquire masses induced by the flat-direction vev that may be sufficiently small for them to be kinematically accessible to inflaton decay. The resulting plasma of inflaton decay products then may act on the flat directions via these superpotential Yukawa couplings, inducing thermal masses and supersymmetry-breaking A terms. In such cases the flat directions start their oscillations at an earlier time than usually estimated. The oscillations are also terminated earlier, due to evaporation of the flat direction condensate produced by its interaction with the plasma of inflaton decay products. In these cases we find that estimates for the resulting baryon/lepton asymmetry of the universe are substantially altered. We identify scenarios for the Yukawa couplings to the flat directions, and the order and mass scale of higher-dimensional superpotential interactions that set the initial flat direction vev, that might lead to acceptable baryo/leptogenesis.