Perturbative unitarity bound on the parameter space in composite two Higgs doublet models

Yıldırım E., Moretti S., Yagyu K., De Curtis S.

IOP Institute of Physics, Joint Annual HEPP and APP conference, Brighton, England, 21 - 23 March 2016, pp.1

  • Publication Type: Conference Paper / Summary Text
  • City: Brighton
  • Country: England
  • Page Numbers: pp.1
  • Karadeniz Technical University Affiliated: No


We discuss a composite two Higgs doublet model based on a symmetry breaking SO(6) × U (1) → SO(4) ×SO(2) × U (1)at a scale f, and explain how the effective kinetic Lagrangian of the model is obtained. The coupling of the Higgs boson as a pseudo Nambu-Goldstone boson to the standard model fields can deviate from that of the standard model Higgs boson due to the non-linear feature. These deviations cause to unitarity violation at high energies because the cancellation of the quadratic energy terms does not happen. We calculate the S-wave amplitude for all the possible two body to two body elastic scalar boson scatterings at the energy \sqrt{s} which involve the longitudinal component of weak gauge boson states as the corresponding Nambu-Goldstone boson states via the Equivalence Theorem Approximation.

We will examine the constrains on parameter space from perturbative unitarity with a fixed energy scale in the composite two Higgs doublet model. By requiring all the eigenvalues of the S-wave matrix to be smaller than a certain value, we obtain constraints on the parameter space such as s, ξ and masses of extra Higgs bosons. We show that stronger upper bounds on the masses of the CP-even and CP-odd Higgs bosons are obtained under the constraints from the unitarity and vacuum stability conditions.