Two-Higgs-doublet_model Knowpia

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 CP even neutral Higgs bosons $h$ and $H$ (where $H$ is heavier than $h$ by convention), the CP odd pseudoscalar $A$ and two charged Higgs bosons $H \pm$ . The discovered Higgs boson is measured to be CP even, so one can map either $h$ or $H$ with the observed Higgs. A special case occurs when $\cos(\beta -\alpha )\rightarrow 0$ , the alignment limit, in which the lighter CP even Higgs boson $h$ has couplings exactly like the SM-Higgs boson.^[4] In another limit such limit, where $\sin(\beta -\alpha )\rightarrow 0$ , the heavier CP even boson, i.e. $H$ is SM-like, leaving $h$ to be the lighter than the discovered Higgs; however, it is important to note that experiments have strongly pointed towards a value for $\sin(\beta -\alpha )$ that is close to 1.^[5]

Such a model can be described in terms of six physical parameters: four Higgs masses ( $m_{\rm {h}},m_{\rm {H}},m_{\rm {A}},m_{\mathrm {H} ^{\pm }}$ ), the ratio of the two vacuum expectation values ( $\tan \beta$ ) and the mixing angle ( $\alpha$ ) 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 edit

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 $\Phi$ , 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	$\Phi _{2}$	$\Phi _{2}$	$\Phi _{2}$	charged fermions only couple to second doublet
Type II	MSSM-like	$\Phi _{2}$	$\Phi _{1}$	$\Phi _{1}$	up- and down-type quarks couple to separate doublets
X	Lepton-specific	$\Phi _{2}$	$\Phi _{2}$	$\Phi _{1}$
Y	Flipped	$\Phi _{2}$	$\Phi _{1}$	$\Phi _{2}$
Type III		$\Phi _{1},\Phi _{2}$	$\Phi _{1},\Phi _{2}$	$\Phi _{1},\Phi _{2}$	Flavor-changing neutral currents at tree level
Type FCNC-free		$\Phi _{1},\Phi _{2}$	$\Phi _{1},\Phi _{2}$	$\Phi _{1},\Phi _{2}$	By finding a matrix pair which can be diagonalized simultaneously. ^[10]

By convention, $\Phi _{2}$ is the doublet to which up-type quarks couple.

References edit

^ "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.
^ Keus, Venus; King, Stephen F.; Moretti, Stefano (2014-01-13). "Three-Higgs-doublet models: symmetries, potentials and Higgs boson masses". Journal of High Energy Physics. 2014 (1): 52. arXiv:1310.8253. Bibcode:2014JHEP...01..052K. doi:10.1007/JHEP01(2014)052. ISSN 1029-8479. S2CID 118482476.
^ Craig, N.; Galloway, J.; Thomas, S. (2013). "Searching for Signs of the Second Higgs Doublet". arXiv:1305.2424 [hep-ph].
^ Collaboration, CMS (2019). "Combined measurements of Higgs boson couplings in proton–proton collisions at √s=13 TeV". The European Physical Journal C. 79 (5): 421. arXiv:1809.10733. doi:10.1140/epjc/s10052-019-6909-y. PMC 6528832. 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.
^ Craig, N.; Thomas, S. (2012). "Exclusive Signals of an Extended Higgs Sector". Journal of High Energy Physics. 1211 (11): 083. arXiv:1207.4835. Bibcode:2012JHEP...11..083C. doi:10.1007/JHEP11(2012)083. S2CID 119312000.
^ Branco, G. C.; Ferreira, P.M.; Lavoura, L.; Rebelo, M.N.; Sher, Marc; Silva, João P. (July 2012). "Theory and phenomenology of two-Higgs-doublet models". Physics Reports. 516 (1). Elsevier: 1–102. arXiv:1106.0034. Bibcode:2012PhR...516....1B. doi:10.1016/j.physrep.2012.02.002. S2CID 119214990.
^ Botella, Francisco J.; Cornet-Gomez, Fernando; Nebot, Miguel (2018-08-30). "Flavor conservation in two-Higgs-doublet models". Physical Review D. 98 (3): 035046. arXiv:1803.08521. Bibcode:2018PhRvD..98c5046B. doi:10.1103/PhysRevD.98.035046. ISSN 2470-0010.

[1] "Higgs Scalars and the Nonleptonic Weak Interactions", Christopher T. Hill, (1977); see pg. 100.

[2] Gunion, J.; H. E. Haber; G. L. Kane; S. Dawson (1990). The Higgs Hunters Guide. Addison-Wesley.

[3] Keus, Venus; King, Stephen F.; Moretti, Stefano (2014-01-13). "Three-Higgs-doublet models: symmetries, potentials and Higgs boson masses". Journal of High Energy Physics. 2014 (1): 52. arXiv:1310.8253. Bibcode:2014JHEP...01..052K. doi:10.1007/JHEP01(2014)052. ISSN 1029-8479. S2CID 118482476.

[4] Craig, N.; Galloway, J.; Thomas, S. (2013). "Searching for Signs of the Second Higgs Doublet". arXiv:1305.2424 [hep-ph].

[5] Collaboration, CMS (2019). "Combined measurements of Higgs boson couplings in proton–proton collisions at √s=13 TeV". The European Physical Journal C. 79 (5): 421. arXiv:1809.10733. doi:10.1140/epjc/s10052-019-6909-y. PMC 6528832. PMID 31178657.

[6] "Hunting the Higgs boson siblings with top quarks | CMS Experiment". cms.cern. Retrieved 2023-09-02.

[7] "CMS-PAS-TOP-22-010". cms-results.web.cern.ch. Retrieved 2023-09-02.

[8] Craig, N.; Thomas, S. (2012). "Exclusive Signals of an Extended Higgs Sector". Journal of High Energy Physics. 1211 (11): 083. arXiv:1207.4835. Bibcode:2012JHEP...11..083C. doi:10.1007/JHEP11(2012)083. S2CID 119312000.

[9] Branco, G. C.; Ferreira, P.M.; Lavoura, L.; Rebelo, M.N.; Sher, Marc; Silva, João P. (July 2012). "Theory and phenomenology of two-Higgs-doublet models". Physics Reports. 516 (1). Elsevier: 1–102. arXiv:1106.0034. Bibcode:2012PhR...516....1B. doi:10.1016/j.physrep.2012.02.002. S2CID 119214990.

[10] Botella, Francisco J.; Cornet-Gomez, Fernando; Nebot, Miguel (2018-08-30). "Flavor conservation in two-Higgs-doublet models". Physical Review D. 98 (3): 035046. arXiv:1803.08521. Bibcode:2018PhRvD..98c5046B. doi:10.1103/PhysRevD.98.035046. ISSN 2470-0010.

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Summary

Classification edit

See also edit

References edit