Speaker
Description
After the Higgs boson discovery, electroweak phase transition (EWPT) became a frontier of high-energy physics and cosmology. While EWPT is a crossover in the Standard Model, some of the promising BSM scenarios, like electroweak baryogenesis, require that it be strongly first-order. Extended Higgs models make it possible to realize such a strongly first-order EWPT. What is the fundamental model of the extended Higgs models? One of the interesting candidates is the composite Higgs model, in which Higgs bosons are pseudo-Nambu-Goldstone bosons of spontaneous breaking of global symmetries at high energies. However, it is not easy to realize strongly first-order EWPT in the Higgs sectors predicted in the composite Higgs models as it is. We here present a new scenario of strongly first-order EWPT in the $SO(6)/SO(5)$ composite Higgs model introducing explicit breaking terms of the symmetries. The low-energy effective field theory is a specific singlet extension of the Higgs sector, whose parameter space is constrained by the theoretical bounds via matching conditions and also by the low-energy experimental data. This scenario gives a strong prediction on the Higgs boson couplings. We discuss the collider signatures at future linear colliders, such as Higgs boson decays and also di-Higgs production.
This work is based on a collaboration with Shinya Kanemura, Yushi Mura, and Tetsuo Shindou, and the paper is in preparation.