Two Higgs doublet model - Alchetron, the free social encyclopedia

In particle physics, a two-Higgs-doublet model (2HDM) is an extension of the Standard Model in which a second Higgs doublet is added.

The addition of the second Higgs doublet leads to five physical states: 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 ± . Such a model has six free parameters: four Higgs masses ( m h , m H , m A , m H ± ), the ratio of the two vacuum expectation values ( tan ⁡ β ) and a mixing angle ( α ).

A special case is when cos ⁡ ( β − α ) = 0 , the so-called alignment limit, in which the lighter CP even Higgs boson h has couplings like the Higgs boson of the Standard Model.

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 Φ , one can divide two-Higgs-doublet models into the following classes:

By convention, Φ 2 is the doublet to which up-type quarks couple.

References

Two-Higgs-doublet model Wikipedia

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