Electroweak baryogenesis from light fermion sources: a critical study

Understand

Electroweak baryogenesis (EWBG) is sourced by nonstandard $CP$-violating interactions of the Higgs boson with fermions, usually taken to be the top quark, enhanced by its large Yukawa coupling.

• Numerous papers have studied EWBG sourced by lighter fermions, including the tau lepton and off-diagonal quark mass terms.
• We critically reassess the viability of EWBG in these scenarios, comparing the predictions based on the semiclassical (WKB) formalism for the source term to those from the VEV insertion approximation (VIA), using updated values for the collision terms, and clarifying discrepancies in the definition of the weak sphaleron rate.
• The VIA systematically predicts a baryon asymmetry that is orders of magnitude larger than the WKB formalism.