The Strongly Coupled Fourth Family and a First-Order Electroweak Phase Transition. I : Quark Sector(Particles and Fields)

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概要

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• In models of dynamical electroweak symmetry breaking due to strongly coupled fourth-family quarks and leptons, their low-energy effective descriptions may involve multiple composite Higgs fields, leading to a possibility that the electroweak phase transition at finite temperature is first-order due to the Coleman-Weinberg mechanism. We examine the behavior of the electroweak phase transition on the basis of the effective renormalizable Yukawa theory, which consists of the fourth-family quarks and two SU (2)-doublet Higgs fields corresponding to the bilinear operators of the fourth-family quarks with/without imposing the compositeness condition. The strength of the first-order phase transition is estimated using the finite-temperature effective potential at one loop with ring improvement. In the Yukawa theory without the compositeness condition, it is found that there is a parameter region where the first-order phase transition is sufficiently strong for the electroweak baryogenesis with the experimentally acceptable Higgs boson and fourth-family quark masses. On the other hand, when the compositeness condition is imposed, the phase transition turns out to be weakly first-order, or possibly second-order, although the result is rather sensitive to the details of the compositeness condition. By combining with the result of the Yukawa theory without the compositeness condition, it is argued that with the fourth-family quark masses in the range of 330-480GeV, corresponding to the compositeness scale in the range of 1.0-2.3TeV, the four-fermion interaction among the fourth-family quarks does not lead to the strongly first-order electroweak phase transition.

• 2009-08-25

著者

• Kikukawa Yoshio

  Institute Of Physics University Of Tokyo

• KOHDA Masaya

  Department of Physics, Saitama University

• YASUDA Junichiro

  Center for the Studies of Higher Education, Nagoya University

• Kohda Masaya

  Department Of Physics Saitama University

• Yasuda Junichiro

  Center For The Studies Of Higher Education Nagoya University

• KIKUKAWA Yoshio

  Institute of Physics, University of Tokyo

関連論文

• The Strongly Coupled Fourth Family and a First-Order Electroweak Phase Transition. I : Quark Sector(Particles and Fields)

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