Higgs Bosons in the Minimal Supersymmetric Standard Model with Explicit CP Violation

TL;DR

This paper analyzes the MSSM Higgs sector with explicit CP violation induced by loop effects involving third-generation squarks, using a CP-non-invariant RG-improved effective potential up to next-to-leading order. It shows that the three neutral Higgs bosons can mix strongly, significantly modifying their couplings to fermions and to W/Z bosons, which in turn reshapes production rates at colliders, especially for the lightest Higgs. The CP-violating Higgs mixing can relax LEP2 bounds on the lightest Higgs mass (potentially to around 60 GeV in some regions) and induce sizable CP-odd components in fermionic couplings, while the mass splitting between the heavier Higgs bosons can be enhanced and resonant CP-violating effects may arise when H_2 and H_3 are nearly degenerate. EDM constraints, notably from electron and neutron measurements, strongly constrain the parameter space, but scenarios with large CP violation in the third generation remain viable and motivate targeted searches at LEP2, Tevatron, LHC, NLC, and FMC.

Abstract

We study the Higgs-boson mass spectrum of the minimal supersymmetric standard model, in which the tree-level CP invariance of the Higgs potential is broken explicitly by loop effects of soft-CP-violating Yukawa interactions related to scalar quarks of the third generation. The analysis is performed by considering the CP-non-invariant renormalization-group improved effective potential through next-to-leading order that includes leading logarithms due to two-loop Yukawa and QCD corrections. We find that the three neutral Higgs particles predicted by the theory may strongly mix with one another, thereby significantly modifying their tree-level couplings to fermions and to the $W^\pm$ and Z bosons. We analyze the phenomenological consequences of such a minimal supersymmetric scenario of explicit CP violation on the production rates of the lightest Higgs particle, and discuss strategies for its potential discovery at high-energy colliders.

Figures (20)

• Figure 1: Two-loop contribution to EDM and CEDM of a light fermion $f$ in the CP-violating MSSM (mirror-symmetric graphs are not shown). Note that $\tilde{\tau}$ does not contribute to the CEDM of a coloured fermion $f$.
• Figure 2: Numerical estimates of (a) $M_{H_1}$ and (b) $2|M_{H_2}-M_{H_3}|/(M_{H_2} + M_{H_3})$ as a function of the CP-violating phase arg($A_t$).
• Figure 3: Numerical estimates of (a) $M_{H_1}$ and (b) $2|M_{H_2}-M_{H_3}|/(M_{H_2} + M_{H_3})$ as a function of $\mu$ in the CP-conserving MSSM.
• Figure 4: Numerical predictions for (a) $g^2_{H_1ZZ} = g^2_{H_2H_3Z}$ and (b) $M_{H_1} \le M_{H_2}$ as a function of arg($A_t$). The definitions of $g_{H_1ZZ}$ and $g_{H_2H_3Z}$ are given in Eqs. (\ref{['gHZZ']}) and (\ref{['gHHZ']}), respectively.
• Figure 5: Numerical predictions for (a) $g^2_{H_3ZZ} = g^2_{H_1H_2Z}$ and (b) $g^2_{H_2ZZ} = g^2_{H_1H_3Z}$ as a function of arg($A_t$). The definition of $g_{H_1ZZ}$ and $g_{H_2H_3Z}$ are given in Eqs. (\ref{['gHZZ']}) and (\ref{['gHHZ']}), respectively.