  A first-order Electroweak Phase Transition (EWPT) could explain the observed
baryon-antibaryon asymmetry and its dynamics could yield a detectable
gravitational wave signature, while the underlying physics would be within the
reach of colliders. The Standard Model, however, predicts a crossover
transition. We therefore study the EWPT in the Standard Model Effective Field
Theory (SMEFT) including dimension-six operators. A first-order EWPT has
previously been shown to be possible in the SMEFT. Phenomenology studies have
focused on scenarios with a tree-level barrier between minima, which requires a
negative Higgs quartic coupling and a new physics scale low enough to raise
questions about the validity of the EFT approach. In this work we stress that a
first-order EWPT is also possible when the barrier between minima is generated
radiatively, the quartic coupling is positive, the scale of new physics is
higher, and there is good agreement with experimental bounds. Our calculation
is done in a consistent, gauge-invariant way, and we carefully analyze the
scaling of parameters necessary to generate a barrier in the potential. We
perform a global fit in the relevant parameter space and explicitly find the
points with a first-order transition that agree with experimental data. We also
briefly discuss the prospects for probing the allowed parameter space using
di-Higgs production in colliders.
