Basis-independent methods for the two-Higgs-doublet model III: The CP-conserving limit, custodial symmetry, and the oblique parameters S, T, U

Nov, 2010
57 pages
Published in:
  • Phys.Rev.D 83 (2011) 055017
e-Print:
Report number:
  • SCIPP-10-18

Citations per year

20102014201820222024051015202530
Abstract: (arXiv)
In the Standard Model, custodial symmetry is violated by the hypercharge U(1) gauge interactions and the Yukawa couplings, while being preserved by the Higgs scalar potential. In the two-Higgs doublet model (2HDM), the generic scalar potential introduces new sources of custodial symmetry breaking. We obtain a basis-independent expression for the constraints that impose custodial symmetry on the 2HDM scalar potential. These constraints impose CP-conservation on the scalar potential and vacuum, and in addition add one extra constraint on the scalar potential parameters. We clarify the mass degeneracies of the 2HDM that arise as a consequence of the custodial symmetry. We also provide a computation of the 'oblique' parameters (S, T, and U) for the most general CP-violating 2HDM in the basis-independent formalism. We demonstrate that the 2HDM contributions to T and U vanish in the custodial symmetry limit, as expected. Using the experimental bounds on S and T from precision electroweak data, we examine the resulting constraints on the general 2HDM parameter space.
  • 11.30.Fs
  • 12.60.Fr
  • 12.15.Lk
  • 11.30.Er
  • Higgs particle: doublet
  • symmetry: custodial
  • potential: scalar
  • coupling: Yukawa
  • oblique
  • CP: violation