Extra vector-like matter and the lightest Higgs scalar boson mass in low-energy supersymmetry

TL;DR

This paper explores how adding vector-like matter in low-energy supersymmetry models can significantly increase the lightest Higgs boson mass while maintaining consistency with electroweak precision data and collider constraints.

Contribution

It demonstrates that extra vector-like supermultiplets can raise the Higgs mass without disrupting gauge coupling unification or electroweak precision fits.

Findings

Higgs mass can be increased significantly with new vector-like matter.

Electroweak precision observables remain compatible with experimental data.

Predicted collider signatures include specific decay patterns of new quarks and leptons.

Abstract

The lightest Higgs scalar boson mass in supersymmetry can be raised significantly by extra vector-like quark and lepton supermultiplets with large Yukawa couplings but dominantly electroweak-singlet masses. I consider models of this type that maintain perturbative gauge coupling unification. The impact of the new particles on precision electroweak observables is found to be moderate, with the fit to Z-pole data as good or better than that of the Standard Model even if the new Yukawa couplings are as large as their fixed-point values and the extra vector-like quark masses are as light as 400 GeV. I study the size of corrections to the lightest Higgs boson mass, taking into account the fixed-point behavior of the scalar trilinear couplings. I also discuss the decay branchings ratios of the lightest new quarks and leptons and general features of the resulting collider signatures.