HEP Theory Journal Club

Baryogenesis and gravity waves from a first-order electroweak phase transition

Benoit Laurent

McGill

Although the electroweak phase transition is predicted to be a smooth crossover in the Standard Model, it can be made first-order by a simple new physics input, like the singlet scalar extension. This type of cosmological phase transition is particularly interesting since it provides a mechanism for electroweak baryogenesis, which could explain the origin of the baryon asymmetry of the Universe. Furthermore, first-order phase transitions produce a stochastic background of gravitational waves that future space-based detectors could probe. These two observable quantities depend closely on the shape and terminal velocity of the electroweak bubble wall, which are highly nontrivial to compute. Moreover, the fluid equations previously used in the literature to describe them suffer from unphysical artifacts that make them unreliable for supersonic walls. In this talk, I present an improved set of equations free from these artifacts and I apply it to the singlet scalar extension. Finally, I show a scan of the parameter space and I discuss the results.