HiggsDubletts

HiggsDubletts is a term sometimes used to describe an extension of the Standard Model Higgs sector in which two SU(2) doublet scalar fields with hypercharge Y = 1 participate in electroweak symmetry breaking. In standard terminology, this is the two-Higgs-doublet model (2HDM). The framework introduces additional scalar degrees of freedom beyond the single Higgs boson of the Standard Model.

After electroweak symmetry breaking, the two complex doublets contribute five physical Higgs states: two neutral CP-even bosons h and H, one neutral CP-odd boson A, and a charged Higgs pair H±. The doublets acquire vacuum expectation values v1 and v2, with v^2 = v1^2 + v2^2 ≈ (246 GeV)^2 and tanβ = v2/v1. The neutral CP-even states are mixtures of the original fields, described by the angle α; the alignment limit, where sin(β−α) → 1, yields one state that closely resembles the Standard Model Higgs boson.

Yukawa couplings and flavor considerations are central to HiggsDubletts phenomenology. To avoid tree-level flavor-changing neutral currents, a Z2 symmetry is often imposed, leading to several 2HDM types (I, II, X, Y) that differ in how fermions couple to the two doublets. The model predicts altered couplings to gauge bosons and fermions, and introduces new decay channels and production modes for the additional scalars.

Theoretical aspects include the form of the Higgs potential, possible CP violation in the scalar sector, and constraints from vacuum stability and perturbativity. Experimental tests focus on precision measurements of the 125 GeV Higgs, direct searches for the heavier scalars, and indirect constraints from electroweak observables. HiggsDubletts also arise naturally in supersymmetric theories, notably the MSSM, where two Higgs doublets are required.