Detectable Gravitational Waves from Very Strong Phase Transitions in the General NMSSM

TL;DR

This work identifies regions in the general NMSSM where the electroweak phase transition is exceptionally strong, aided by a tree- and loop-level dynamics that realize an approximate $Z_2$ symmetry in the light sector. It introduces a subtraction/renormalization scheme to tame sizable radiative corrections from heavy fields and to stabilize the effective potential across both broken and symmetric phases. Benchmark points show a very strong EWPT with substantial latent heat and small $\beta/H$, yielding gravitational-wave spectra that can be within eLISA’s reach for certain designs. The results highlight a tangible link between high-scale SUSY dynamics, EWPT strength, and observable GW signals, offering a path to test NMSSM scenarios via future space-based GW detectors and collider phenomenology alike.

Abstract

We study the general NMSSM with an emphasis on the parameter regions with a very strong first-order electroweak phase transition (EWPT). In the presence of heavy fields coupled to the Higgs sector, the analysis can be problematic due to the existence of sizable radiative corrections. In this paper we propose a subtraction scheme that helps to circumvent this problem. For simplicity we focus on a parameter region that is by construction hidden from the current collider searches. The analysis proves that (at least) in the identified parameter region the EWPT can be very strong and striking gravitational wave signals can be produced. The corresponding gravitational stochastic background can potentially be detected at the planned space-based gravitational wave observatory eLISA, depending on the specific experiment design that will be approved.

Figures (6)

• Figure 1: The relevant self-energy diagrams of the soft field. The double line denotes the heavy field.
• Figure 2: Resummation of Daisy diagrams.
• Figure 3: The relevant two-particle-irreducible vacuum diagrams. The propagators are full propagators.
• Figure 4: The finite temperature potential in the benchmark point C. The upper [lower] plot shows the effective potential along the singlet direction $V(h=0,s)$ [along the SM-like Higgs direction $V(h,s=\left<S\right>_{\cancel{EW},T})$]. The potential minima at tree level and at one loop are the same as a consequence of the subtraction scheme we adopt.
• Figure 5: Spectrum of the stochastic gravitational wave backgrounds (black lines) coming from bubble collisions generated during the EWPT in the benchmark points of table \ref{['tab:params']}. The sensitivity curves of the eLISA designs described in the text are displayed in blue.