Abstract
Grand gauge–Higgs unification of five dimensional SU(6) gauge theory on an orbifold S^1/Z_2 with localized gauge kinetic terms is discussed. The Standard model (SM) fermions on one of the boundaries and some massive bulk fermions coupling to the SM fermions on the boundary are introduced, so that they respect an SU(5) symmetry structure. The SM fermion masses including top quark are reproduced by mild tuning the bulk masses and parameters of the localized gauge kinetic terms. Gauge coupling universality is not guaranteed by the presence of the localized gauge kinetic terms and it severely constrains the Higgs vacuum expectation value. Higgs potential analysis shows that the electroweak symmetry breaking occurs by introducing additional bulk fermions in simplified representations. The localized gauge kinetic terms enhance the magnitude of the compactification scale, which helps Higgs boson mass large. Indeed the observed Higgs boson mass 125 GeV is obtained.
Highlights
Gauge–Higgs unification (GHU) [1,2,3,4,5,6] is one of the candidates among the physics beyond the Standard Model (SM), which solves the hierarchy problem by identifying the SM Higgs field with one of the extra spatial component of the higher dimensional gauge field
One of the authors discussed a grand gauge–Higgs unification (GGHU) [40],1 where the five dimensional SU (6) GGHU was considered and the SM fermions were embedded in zero modes of SU (6) multiplets in the bulk
Integrating out these massive bulk fermions leads to non-local SM fermion masses, which are proportional to the bulk to boundary couplings and exponentially sensitive to their bulk masses
Summary
Gauge–Higgs unification (GHU) [1,2,3,4,5,6] is one of the candidates among the physics beyond the Standard Model (SM), which solves the hierarchy problem by identifying the SM Higgs field with one of the extra spatial component of the higher dimensional gauge field. We have shown that the electroweak symmetry breaking and an observed Higgs mass can be realized by introducing additional bulk fermions with large dimensional representation. We have attempted to analyze for the cases of three and four rank tensor representations, but an observed top quark mass was not obtained As another known approach [52], introducing the localized gauge kinetic terms has enhancement effects on fermion masses. We will show that the fermion mass hierarchy including top quark mass is realized by appropriately choosing the bulk mass parameters and the size of the localized gauge kinetic terms. 4, after briefly explaining the generation mechanism of the SM fermion masses, it is shown that the SM fermion masses including top quark can be reproduced by mild tuning of bulk masses and parameters of the localized gauge kinetic terms.
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