Type II two-Higgs-doublet model

Type II two-Higgs-doublet model
Name	Type II two-Higgs-doublet model
Field	Particle physics
Introduced	1970s
Key people	Glashow, Weinberg, Gunion
Related	Standard Model; Minimal Supersymmetric Standard Model

Type II two-Higgs-doublet model

The Type II two-Higgs-doublet model is an extension of the Standard Model that introduces two complex Higgs doublets to explain electroweak symmetry breaking, accommodate mass generation, and address phenomena related to flavor and CP violation. It plays a central role in the Minimal Supersymmetric Standard Model and has implications tested by experiments such as Large Hadron Collider, ATLAS experiment, and CMS experiment. The model connects to theoretical frameworks proposed by researchers including Sheldon Glashow, Steven Weinberg, and John Gunion.

Introduction

The Type II two-Higgs-doublet model augments the Glashow–Weinberg condition by assigning one Higgs doublet to up-type fermions and the other to down-type fermions and charged leptons, a structure mirrored in the MSSM and in constructions inspired by Grand Unified Theory scenarios like SU(5). It is motivated by issues raised in work by Gerard 't Hooft, Abdus Salam, and Hermann Weyl regarding symmetry breaking, and by phenomenological needs highlighted in precision measurements at facilities such as LEP and Tevatron.

Theoretical Framework

The Lagrangian of the model extends the Electroweak interaction sector of the Standard Model by introducing two scalar SU(2)L doublets, commonly denoted H_u and H_d, with hypercharge assignments matching conventions used by the Particle Data Group. The scalar potential includes quadratic and quartic terms parameterized by coefficients analogous to those in treatments by Peter Higgs and analyzed in studies by Howard Georgi and Lisa Randall. Gauge interactions link the doublets to the W and Z, as in electroweak theory developed by Sheldon Glashow and Steven Weinberg. Global symmetries, discrete Z2 parity assignments, and soft-breaking terms control tree-level flavor-changing neutral currents following arguments by Glashow–Weinberg. Renormalization-group evolution of the quartic couplings is performed in lines similar to analyses by Kenneth Wilson and David Gross.

Yukawa Couplings and Flavor Structure

In Type II the Yukawa sector assigns H_u to couple only to up-type quarks and H_d to couple to down-type quarks and charged leptons, reflecting textures considered in works by Michael Dine and Howard Haber. This separation is implemented via a discrete symmetry originally advocated in discussions by Glashow and Weinberg that forbids tree-level flavor-changing neutral currents, an idea related to constraints explored by Lincoln Wolfenstein in flavor physics. The resulting Yukawa matrices feed into the CKM matrix, connecting to CP-violation studies by Makoto Kobayashi and Toshihide Maskawa, and to rare-decay constraints measured by experiments like Belle II and LHCb. Flavor-changing processes such as neutral meson mixing in systems studied by CERN collaborations and by groups at SLAC National Accelerator Laboratory impose limits on off-diagonal entries and on the parameter tanβ, a ratio commonly used in analyses alongside conventions from the Particle Data Group.

Scalar Spectrum and Masses

The physical scalar spectrum contains a light CP-even scalar often identified with the 125 GeV boson observed by ATLAS experiment and CMS experiment, a heavy CP-even scalar, a CP-odd pseudoscalar, and a charged Higgs pair. Masses arise from diagonalization of the mass matrices determined by the scalar potential parameters and by electroweak symmetry breaking, techniques developed in literature by John Gunion, Howard Haber, and Gordon Kane. Radiative corrections from top and stop sectors are significant in supersymmetric embeddings analyzed by Hitoshi Murayama and Joseph Lykken. Benchmark scenarios used in searches reference conventions from collaborations including Higgs Cross Section Working Group and incorporate precision inputs from LEP Electroweak Working Group.

Phenomenology and Experimental Constraints

Collider searches at Large Hadron Collider with detectors ATLAS experiment and CMS experiment probe production modes such as gluon fusion, associated production with top quarks studied by CDF and D0 at Tevatron, and charged Higgs searches in top decays. Flavor observables from Belle II, BaBar, and LHCb constrain tanβ and charged Higgs mass via processes including B→X_sγ and B→τν, topics investigated in analyses by Gino Isidori and Fulvia De Fazio. Electroweak precision observables measured at LEP and corrections computed in frameworks by Peskin and Takeuchi place constraints on oblique parameters S and T. Direct detection limits from hadron collider searches are complemented by global fits using statistical techniques from groups at CERN and Fermilab; these fits use tools developed by collaborations such as HiggsTools and methodologies advocated by Glen Cowan.

Extensions and Variants

Variants of the Type II structure appear in supersymmetric constructions like the Minimal Supersymmetric Standard Model, in models with additional singlets studied by Pavel Fileviez Perez, and in frameworks incorporating CP violation as explored by Anupam Mazumdar. Alternative Yukawa assignments (Type I, Type X, Type Y) and aligned two-Higgs-doublet models are discussed in literature by Andreas Crivellin and David Straub. Embeddings into Grand Unified Theory schemes such as SO(10) GUT and consequences for dark matter candidates connect to research by Savas Dimopoulos and Mark Wise. Future tests at proposed machines like the International Linear Collider, Future Circular Collider, and experiments planned at KEK will further probe parameter space regions highlighted by theoretical studies from groups led by Michelangelo Mangano and Abdelhak Djouadi.

Category:Beyond the Standard Model