Two-Higgs-doublet model
The two-Higgs-doublet model (2HDM) is an extension of the Standard Model of particle physics.[1][2] 2HDM models are one of the natural choices for beyond-SM models containing two Higgs doublets instead of just one. There are also models with more than two Higgs doublets, for example three-Higgs-doublet models etc.[3]
The addition of the second Higgs doublet leads to a richer phenomenology as there are five physical scalar states viz., the
Such a model can be described in terms of six physical parameters: four Higgs masses (), the ratio of the two vacuum expectation values () and the mixing angle () which diagonalizes the mass matrix of the neutral CP even Higgses. The SM uses only 2 parameters: the mass of the Higgs and its vacuum expectation value.
The masses of the H and A bosons could be below 1 TeV and the CMS has conducted searches around this range but no significant excess above the standard model prediction has been observed.[6][7]
Classification
Two-Higgs-doublet models can introduce flavor-changing neutral currents which have not been observed so far. The Glashow-Weinberg condition, requiring that each group of fermions (up-type quarks, down-type quarks and charged leptons) couples exactly to one of the two doublets, is sufficient to avoid the prediction of flavor-changing neutral currents.
Depending on which type of fermions couples to which doublet , one can divide two-Higgs-doublet models into the following classes:[8][9]
Type | Description | up-type quarks couple to | down-type quarks couple to | charged leptons couple to | remarks |
---|---|---|---|---|---|
Type I | Fermiophobic | charged fermions only couple to second doublet | |||
Type II | MSSM-like | up- and down-type quarks couple to separate doublets | |||
X | Lepton-specific | ||||
Y | Flipped | ||||
Type III | Flavor-changing neutral currents at tree level | ||||
Type FCNC-free | By finding a matrix pair which can be diagonalized simultaneously. [10] |
By convention, is the doublet to which up-type quarks couple.
See also
References
- ^ "Higgs Scalars and the Nonleptonic Weak Interactions", Christopher T. Hill, (1977); see pg. 100.
- ^ Gunion, J.; H. E. Haber; G. L. Kane; S. Dawson (1990). The Higgs Hunters Guide. Addison-Wesley.
- S2CID 118482476.
- ].
- PMID 31178657.
- ^ "Hunting the Higgs boson siblings with top quarks | CMS Experiment". cms.cern. Retrieved 2023-09-02.
- ^ "CMS-PAS-TOP-22-010". cms-results.web.cern.ch. Retrieved 2023-09-02.
- S2CID 119312000.
- S2CID 119214990.
- ISSN 2470-0010.