  Electroweak baryogenesis (EWBG) in extensions of the Standard Model will be
tested quantitatively in upcoming nuclear and particle physics experiments, but
only to the extent that theoretical computations are robust. Currently there
exist orders-of-magnitude discrepancies between treatments of charge transport
dynamics during EWBG performed by different groups, each relying on different
sets of approximations. In this work, we introduce a consistent power counting
scheme (in ratios of length scales) for treating systematically the dynamics of
EWBG: CP-asymmetric flavor oscillations, collisions, and diffusion. Within the
context of a simplified model of EWBG, we derive the relevant Boltzmann
equations using non-equilibrium field theory, and solve them exactly without
ansatz for the functional form of the density matrices. We demonstrate the
existence of a resonant enhancement in charge production when the flavor
oscillation length is comparable to the wall thickness. We compare our results
with the existing treatment of EWBG by Konstandin, Prokopec, Schmidt, and Seco
(KPSS) who previously identified the importance of flavor oscillations in EWBG.
We conclude: (i) the power counting of KPSS breaks down in the resonant regime,
and (ii) this leads to substantial underestimation of the charge generated in
the unbroken phase, and potentially of the final baryon asymmetry.
