A new perspective on the electroweak phase transition in the Standard Model Effective Field Theory

TL;DR

This paper demonstrates that a first-order electroweak phase transition in the Standard Model Effective Field Theory can occur radiatively with a positive quartic coupling, higher new physics scale, and still satisfy experimental constraints, offering new insights into baryogenesis and gravitational wave signals.

Contribution

It shows that a first-order EWPT is possible in SMEFT with radiatively generated barriers, positive quartic coupling, and higher new physics scales, expanding previous phenomenological scenarios.

Findings

First-order EWPT can occur with radiative barriers and positive quartic coupling.

The parameter space consistent with experimental bounds is explicitly identified.

Potential collider signatures via di-Higgs production are briefly discussed.

Abstract

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.