Supersymmetric Baryogenesis at the Electroweak Phase Transition

TL;DR

This work investigates electroweak baryogenesis within the MSSM by exploiting non-universal soft terms that yield a light right-handed up-type squark through sizable $\tilde{c}_R-\tilde{t}_R$ or $\tilde{u}_R-\tilde{t}_R$ mixing. A single CP-violating phase in the up-type quark mass matrix, together with a non-commuting LR and RR squark mass structure, generates a space-time dependent CP-violating source term during the electroweak phase transition, driving the baryon asymmetry without new CP phases. The analysis shows that the EWPT can be strongly first order (with $h(T_0)/T_0 \sim O(1)$) and yields a baryon-to-entropy ratio around the observed level for plausible parameter choices; it also connects to low-energy flavor observables, predicting near-current bounds for $D^0-\bar{D}^0$ mixing and the neutron EDM, and yielding distinctive CP violation in the $B-\bar{B}$ system. These results link collider-scale SUSY breaking patterns to cosmological baryogenesis and low-energy flavor physics, offering testable predictions for upcoming experiments.

Abstract

We study the possibility of baryogenesis in the case of supersymmetry breaking with large mixing between the right-handed scalar charm and right-handed scalar top or right-handed scalar up and right-handed scalar top squarks resulting in one light right-handed up-type squark mass eigenstate. We argue that in this case the electroweak phase transition will be first order, and that large phases already present in the quark mass matrices can generate a baryon asymmetry of the correct magnitude without introducing any new phases specifically for this purpose. We study in detail a particular ansatz for supersymmetry breaking and CP violation where there is only one CP violating phase in the theory: in the up-type quark mass matrix. We study the constraints placed on this model by baryogenesis and flavor physics. This scenario has robust implications for low energy flavor phsyics including D-Dbar mixing and an electric dipole moment for the neutron that are close to the experimental bounds, and CP violation in the B-Bbar system that is different from that in the Standard Model.