Abstract
Within classically conformal models, the spontaneous breaking of scale invariance is usually associated to a strong first order phase transition that results in a gravitational wave background within the reach of future space-based interferometers. In this paper we study the case of the classically conformal gauged B–L model, analysing the impact of this minimal extension of the Standard Model on the dynamics of the electroweak symmetry breaking and derive its gravitational wave signature. Particular attention is paid to the problem of vacuum stability and to the role of the QCD phase transition, which we prove responsible for concluding the symmetry breaking transition in part of the considered parameter space. Finally, we calculate the gravitational wave signal emitted in the process, finding that a large part of the parameter space of the model can be probed by LISA.
Highlights
In regard of this, classically conformal – or scale-invariant – models [37,38,39,40,41,42,43] are an example of framework which typically induces a sizeable gravitational signature [20,30,44, 45], as thermal corrections here inevitably result in a potential barrier that separates the vacuum states of the theory
Particular attention is paid to the problem of vacuum stability and to the role of the QCD phase transition, which we prove responsible for concluding the symmetry breaking transition in part of the considered parameter space
After introducing the framework and briefly reviewing its general phenomenology, we focused on the phase transition dynamics that the scenario supports and on the high-energy properties of the theory
Summary
Classically conformal – or scale-invariant – models [37,38,39,40,41,42,43] are an example of framework which typically induces a sizeable gravitational signature [20,30,44, 45], as thermal corrections here inevitably result in a potential barrier that separates the vacuum states of the theory. The effective potential, including the contributions of thermal corrections and QCD phase transition, is presented, whereas the relative analyses of perturbativity and vacuum stability are detailed in Sect. 5. The electroweak phase transition is studied, and the resulting gravitational wave signature of the model is computed in Sect.
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