  We investigate the role of leptons in electroweak baryogenesis by studying a
relatively simple framework inspired by effective field theory that satisfies
all Sakharov conditions. In particular, we study the effectiveness of
CP-violating source terms induced by dimension-six Yukawa interactions for
quarks and charged leptons. Despite the relatively small Yukawa coupling,
CP-violating source terms involving taus are quite effective and can account
for the observed matter-antimatter asymmetry. We obtain analytical and
numerical expressions for the total baryon asymmetry, the former providing
important insight into what makes lepton CP violation relatively effective
compared to quark CP violation. Leptons also play an important role if the
CP-violating source involves top quarks. While the tau Yukawa coupling in the
Standard Model is small, it significantly enhances the baryon asymmetry by
transferring the chiral asymmetry in quarks, which is washed out by strong
sphalerons, to a chiral asymmetry in leptons. We conclude that leptons should
not be ignored even if CP violation is limited to the quark sector. The role of
leptons can be further increased in scenarios of new physics with additional
chiral-symmetry-breaking interactions between quarks and leptons, as can happen
in models with additional Higgs bosons or leptoquarks. Finally, we study
CP-violating dimension-six Yukawa interactions for lighter quarks and leptons
but conclude that these lead to too small baryon asymmetries.
