Phase Transitions in the NMSSM

TL;DR

The paper analyzes finite-temperature phase transitions in the NMSSM with a weak-scale singlet, under Higgs-spectrum and vacuum-stability constraints. It reveals four distinct transition patterns, including three two-stage types, and shows that a strongly first-order electroweak transition can occur without a light stop in certain NMSSM regions, especially with tree-level CP violation in the Higgs sector. By mapping CP-conserving and CP-violating scenarios, it highlights the potential for electroweak baryogenesis within NMSSM parameter space, while noting that some transitions (e.g., via phase II) may not support baryogenesis due to phase degeneracy. The work also discusses the need for further study of sphaleron dynamics and broader parameter exploration to assess the viability and robustness of these baryogenesis scenarios.

Abstract

We study phase transitions in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) with the weak scale vacuum expectation values of the singlet scalar, constrained by Higgs spectrum and vacuum stability. We find four different types of phase transitions, three of which have two-stage nature. In particular, one of the two-stage transitions admits strongly first order electroweak phase transition, even with heavy squarks. We introduce a tree-level explicit CP violation in the Higgs sector, which does not affect the neutron electric dipole moment. In contrast to the MSSM with the CP violation in the squark sector, a strongly first order phase transition is not so weakened by this CP violation.

Figures (8)

• Figure 1: The allowed region in the $(\lambda,\kappa)$-plane for $v_{0n}=200\hbox{GeV}$, $\tan\beta_0=5$, $A_\kappa=-100\hbox{GeV}$ and $m_{H^\pm}=600\hbox{GeV}$ in the heavy squark case.
• Figure 2: The contour plot of the reduced effective potential at $T=0$ for the parameter set A (left-hand side) and D (right-hand side).
• Figure 3: The contour plot of the reduced effective potential at $T=0$ for the parameter set B (left-hand side) and C (right-hand side).
• Figure 4: The effective potentials at the local minima corresponding to the phase-EW (solid curve) and the phase-I (dashed curve) for the parameter set A. The right-hand plot is the close view of the left-hand one near the transition temperature.
• Figure 5: The effective potentials at the local minima corresponding to the phase-EW (solid curve), the phase-I${}^\prime$ (dashed curve), the phase-II (dotted curve) and the phase-SYM (thick dotted-dashed curve) for the parameter set B. The right-hand plot is the close view of the left-hand one near the transition temperature.