[Paper Review] Electroweak baryogenesis and the triple Higgs boson coupling

Shinya Kanemura, Yasuhiro Okada+1 more|ArXiv.org|Jul 22, 2005

Particle physics theoretical and experimental studies3 citations

TL;DR

This paper investigates electroweak baryogenesis in the two Higgs doublet model (2HDM) and minimal supersymmetric standard model (MSSM), showing that a strongly first-order electroweak phase transition—required for baryogenesis—induces large quantum corrections to the trilinear Higgs coupling (hhh). In the 2HDM, deviations from the Standard Model value exceed 10% in viable baryogenesis regions, making them detectable at a future International Linear Collider (ILC).

ABSTRACT

We study collider signatures of electroweak baryogenesis in the two Higgs doublet model and the minimal supersymmetric standard model. It is found that the trilinear coupling of the lightest Higgs boson receives large quantum corrections if the electroweak phase transition is strongly first order for successful baryogenesis. In the two Higgs doublet model, the magnitude of the deviation from the standard model value is shown to be larger than 10 percent. Such a deviation can be detected at a future electron-positron linear collider.

Motivation & Objective

• To explore the connection between electroweak baryogenesis and the trilinear Higgs boson coupling (hhh) in extended Higgs sectors.
• To determine whether large quantum corrections to the hhh coupling arise in models supporting a strong first-order electroweak phase transition.
• To assess the detectability of such deviations at future linear collider experiments like the ILC.
• To compare the 2HDM and MSSM in terms of the magnitude of hhh coupling deviations under baryogenesis conditions.
• To identify parameter regions where the sphaleron decoupling condition for baryogenesis is satisfied and hhh coupling deviations are significant.

Proposed method

• Calculated the finite-temperature effective potential in the 2HDM using one-loop corrections with ring (Daisy) summation to improve accuracy.
• Used high-temperature expansion and numerical computation to determine the critical temperature $T_c$ and vacuum expectation value $\varphi_c$ at the phase transition.
• Evaluated the one-loop radiative corrections to the trilinear Higgs coupling $\lambda_{hhh}^{\text{eff}}$ in the on-shell scheme, comparing with the SM prediction.
• Defined the deviation $\Delta\lambda_{hhh}^{\text{2HDM}} / \lambda_{hhh}^{\text{SM}}$ to quantify departure from the Standard Model.
• Applied similar analysis to the MSSM, estimating the hhh coupling shift via stop loop contributions to the effective potential.
• Combined the sphaleron decoupling condition $\varphi_c / T_c \geq 1$ with the hhh coupling deviation to identify observable parameter regions.

Experimental results

Research questions

• RQ1 What is the magnitude of the quantum correction to the trilinear Higgs coupling in the 2HDM when the electroweak phase transition is strongly first order?
• RQ2 Can such deviations in the hhh coupling be detected at a future electron-positron linear collider like the ILC?
• RQ3 How does the hhh coupling deviation scale with the mass of heavy Higgs bosons and the stop mass in the MSSM?
• RQ4 What parameter regions in the 2HDM and MSSM satisfy both the sphaleron decoupling condition and large hhh coupling deviations?
• RQ5 Is there a direct phenomenological signature of electroweak baryogenesis in the Higgs sector accessible via precision Higgs measurements?

Key findings

• In the 2HDM, the trilinear Higgs coupling deviates from the Standard Model value by more than 10% in regions where the electroweak phase transition is strongly first order.
• The deviation arises due to large quantum corrections from heavy Higgs bosons and top quarks in the loop when the phase transition is strongly first order.
• For $m_h = 120$ GeV, the phase transition becomes sufficiently strong for baryogenesis when heavy Higgs masses exceed approximately 200 GeV.
• The condition $\varphi_c / T_c \geq 1$ for sphaleron decoupling is satisfied for $m_\Phi \gtrsim 185$ GeV when $M=0$, and for $m_\Phi \gtrsim 300$ GeV when $M=150$ GeV.
• In the MSSM, the hhh coupling deviation is estimated at around 6% for $m_h = 120$ GeV, driven by light stop loop contributions.
• The combined parameter space where baryogenesis is viable and the hhh coupling deviates significantly from the SM is detectable at a future linear collider with $\sim$10–20% precision on the hhh coupling.