Protecting the Baryon Asymmetry in Theories with R-parity Violation

We propose a mechanism for hiding the primordial baryon asymmetry from interactions that could wash it out. It requires the introduction of a baryon number carrying singlet which is in equilibrium in the early universe and shares any existing baryon asymmetry. It decouples from the Standard Model particles before all the interactions required to wash out the asymmetry are in equilibrium ($T \simeq 10$ TeV), and decays after the electroweak phase transition, but before nucleosynthesis. This mechanism can conserve a baryon asymmetry in models (a) with $B-L = 0$, such as many $SU(5)$ GUTs, or (b) with $B-L$ violating interactions in thermal equilibrium, such as SUSY with broken $R$-parity. As a result, cosmological constraints on $R$-parity violating operators are relaxed considerably.