Status of electroweak baryogenesis in minimal composite Higgs

Abstract

We present an update on the status of electroweak baryogenesis in minimal composite Higgs models. The particularity of this framework is that the electroweak phase transition can proceed simultaneously with the confinement phase transition of the new strong dynamics that produces the composite Higgs. The latter transition is controlled by the dilaton — the pseudo-Goldstone boson of an approximate scale invariance of the composite sector. Since it naturally is first-order, the electroweak phase transition becomes first-order too. Another appealing aspect is that the necessary additional source of CP violation can arise from the variation of the quark Yukawa couplings during the phase transition, which is built-in naturally in this scenario. These two features address the shortcomings of electroweak baryogenesis in the Standard Model. We confront this scenario with the latest experimental bounds derived from collider searches for new resonances and measurements of the Higgs couplings and electric dipole moments. All these constraints provide (or will be able to provide in the near future) important bounds on the considered scenario, with the most stringent ones coming from LHC searches for new resonances which constrain the dilaton mass and couplings. We identify the viable region of parameter space which satisfies all the constraints, and is characterized by a dilaton mass in the 300–500 GeV range and a Higgs decay constant f ≲ 1.1 TeV. We discuss its future tests.

Bridging the μHz gap in the gravitational-wave landscape: unveiling dark baryons

“…Finally, another possibility to address the observed baryon asymmetry of the universe, as demonstrated in refs. [66][67][68][69][70][71], involves EW baryogenesis in the context of CH models.…”

Cosmological phase transitions in composite Higgs models

“…The ordinary electroweak phase transition may follow from those phase transitions or simultaneously take place. Although the effect of a new strongly-interacting sector in the model on the electroweak phase transition has been extensively investigated in literature [9][10][11][12], including the application to electroweak baryogenesis [13][14][15][16][17][18], the dynamics of the phase transitions (i), (ii) has been largely unexplored in the context of a composite Higgs model, while its understanding is essential to clarify the evolution of our Universe and possibly brings about a new application to a cosmological issue as well as a further prediction of the model that is experimentally tested. 1 In particular, if either of the phase transitions (i), (ii) is of the first-order, it proceeds through the nucleation and expansion of true vacuum bubbles, which provides a significant departure from the thermal equilibrium, where the bubble collision [37][38][39][40], sound wave [41][42][43][44] and plasma turbulence [45][46][47][48][49][50] may generate an observable stochastic gravitational wave (GW) background.…”