FERMILAB-PUB-19-602-T Electroweak phase transition with spontaneous Z2-breaking Marcela Carena,a;b;c Zhen Liud and Yikun Wanga;b aTheoretical Physics Department, Fermi National Accelerator Laboratory, Batavia, Illinois, 60510, USA bEnrico Fermi Institute, University of Chicago, Chicago, Illinois, 60637, USA cKavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois, 60637, USA dMaryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742, USA E-mail:
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[email protected] Abstract: This work investigates a simple, representative extension of the Standard Model with a real scalar singlet and spontaneous Z2 breaking, which allows for a strongly first-order phase transition, as required by electroweak baryogenesis. We perform ana- lytical and numerical calculations that systematically include one-loop thermal effects, Coleman-Weinberg corrections, and daisy resummation, as well as evaluation of bubble nucleation. We study the rich thermal history and identify the conditions for a strongly first-order electroweak phase transition with nearly degenerate extrema at zero tem- arXiv:1911.10206v2 [hep-ph] 15 Oct 2020 perature. This requires a light scalar with mass below 50 GeV. Exotic Higgs decays, as well as Higgs coupling precision measurements at the LHC and future collider facili- ties, will test this model. Additional information may be obtained from future collider constraints on the Higgs self-coupling. Gravitational-wave signals are