New Insights of Electroweak Phase Transition in NMSSM

TL;DR

This paper analyzes the electroweak phase transition in the NMSSM, identifying key parameters that influence a strong first-order transition and implications for Higgs boson searches at the LHC.

Contribution

It introduces a new dimensionless parameter $R_\kappa$ to characterize the phase transition and links it to Higgs spectra, providing novel insights into the conditions for a strong first-order EWPT in NMSSM.

Findings

Strong first-order EWPT occurs near $R_\kappa \sim -1$ or positive $R_\kappa \lesssim 10$.

A light CP odd or even Higgs boson ($\sim 60-100$ GeV) is favored in these scenarios.

Implications for LHC searches for light Higgs states are discussed.

Abstract

We perform a detailed semi-analytical analysis of the electroweak phase transition (EWPT) property in NMSSM, which serves as a good benchmark model in which the 126 GeV Higgs mixes with a singlet. In this case, a strongly first order electroweak phase transition (SFOEWPT) is achieved by the tree-level effects and the phase transition strength $\gamma_c$ is determined by the vacua energy gap at $T=0$. We make an anatomy of the energy gap at both tree-level and loop-level and extract out a dimensionless phase transition parameter $R_\kappa \equiv 4 \kappa v_s / A_\kappa$, which can replace $A_\kappa$ in the parameterization and affect the light CP odd and even Higgs spectra. We find that SFOEWPT only occurs in $R_\kappa \sim -1$ and positive $R_\kappa \lesssim \mathcal{O}(10)$, which in the non-PQ limit case would prefer either a relatively light CP odd or CP even Higgs boson $\sim (60, 100)$ GeV, therefore serves as a smoking gun signal and requires new search strategies at the LHC.