Electroweak phase transition enhanced by a CP-violating dark sector

TL;DR

The paper investigates electroweak phase transitions in a CP-violating dark-sector 3-Higgs-doublet model (3HDM), using dimensional reduction to a 3D effective theory and a two-loop finite-temperature potential. By scanning a wide parameter space and applying rigorous theoretical and experimental constraints, it demonstrates that strong first-order EWPTs are attainable in sizeable regions, though two-loop effects typically weaken the transition relative to one-loop estimates. The authors show that two-loop corrections reduce the transition strength by about 27% and lower the critical temperature by roughly 7%, refining the identification of viable benchmarks for electroweak baryogenesis. They also explore two-step transitions and identify a benchmark with maximal CP violation that remains promising for baryogenesis, while noting the need for transport dynamics studies to fully establish baryogenesis viability. The methodology, based on dimensional reduction, symbolic matching, and numerical evaluation with BLOOP/DRalgo, provides a robust framework for analyzing EWPT in extended scalar sectors and can be extended to other BSM scenarios and lattice studies.

Abstract

Within a well-motivated 3-Higgs doublet model, in which the extended dark sector accommodates CP violation, we analyse the electroweak phase transition (EWPT) at one- and two-loop order. We show the importance of higher loop calculations in EWPT analyses and identify the regions of the parameter space of our model where EWPT is of first order while in agreement with all theoretical and experimental bounds, including Dark Matter relic density and direct and indirect searches.

Figures (7)

• Figure 1: Heat maps of the phase transition strength at one-loop as a function of scan parameters. The step size is $0.1\,\mathrm{\;GeV}$.
• Figure 2: Heat maps of the phase transition strength at two-loop as a function of scan parameters. The step size is $0.1\,\mathrm{\;GeV}$.
• Figure 3: Heat maps of critical temperature $T_c$ as a function of $m_{S_1}$ and $g_{h\mathrm{DM}}$ at one-loop (top) and two-loop (bottom).
• Figure 4: Temperature-normalised effective potential at one-loop (left) and two-loop (right) for the benchmark in Eq. \ref{['eq:MaximalCPV']}. Filled circles indicate the global minimum.
• Figure 5: Heat maps of the strength of the $(v_1, v_2, 0) \to (0, 0, v_3)$ transition at one-loop. Step size: $1\,\mathrm{\;GeV}$.