Real Higgs singlet and the electroweak phase transition in the standard model, (UM-P-93/80, OZ-93/20)

TL;DR

The paper investigates whether the SM can accommodate electroweak baryogenesis by extending the Higgs sector with a real singlet that couples to the SM doublet, constructing the finite-temperature effective potential with tree-level cubic terms and one-loop thermal corrections. It analyzes the conditions for a strong first-order phase transition by exploring degenerate minima at the transition temperature $T_c$ and demonstrates regions where $v(T_c)/T_c \gtrsim 1$ while maintaining $m_H \gtrsim 60$ GeV. The main finding is that the real singlet introduces tree-level cubic terms that facilitate a strong transition, making electroweak baryogenesis more viable in this minimal extension, with robustness against Higgs self-energy corrections. This work provides a concrete mechanism and parameter-space guidance for electroweak baryogenesis in a minimal SM-like framework.

Abstract

The effective potential at finite temperature is constructed within the minimal standard model when a real Higgs singlet is added on. We find that a region of parameter space exists for which one can find a first order transition strong enough to prevent the erasure due to sphalerons of baryon asymmetry, while keeping the mass of the smallest Higgs boson above the experimental lower bound of about 60 GeV.