CKM matrix and FCNC suppression in $SO(5) \times U(1) \times SU(3)$ gauge-Higgs unification

TL;DR

This paper investigates how the CKM matrix and suppression of FCNCs can be naturally realized in a gauge-Higgs unification model based on an $SO(5) imes U(1) imes SU(3)$ gauge symmetry, highlighting the role of gauge invariance.

Contribution

It demonstrates that gauge invariance in an $SO(5) imes U(1) imes SU(3)$ gauge-Higgs unification model naturally suppresses FCNCs and reproduces the CKM matrix with specific adjustments.

Findings

FCNCs are suppressed by a factor of about 10^{-6}

CKM matrix is successfully reproduced with a larger up quark mass

Flavor-changing Yukawa couplings are extremely small

Abstract

The Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix and flavor-changing neutral currents (FCNC's) in the quark sector are examined in the GUT inspired $SO(5) \times U(1) \times SU(3)$ gauge-Higgs unification in which the 4D Higgs boson is identified with the Aharonov-Bohm phase in the fifth dimension. Gauge invariant brane interactions play an important role for the flavor mixing in the charged-current weak interactions. The CKM matrix is reproduced except that the up quark mass needs to be larger than the observed one. FCNC's are naturally suppressed as a consequence of the gauge invariance, with a factor of order $10^{-6}$. It is also shown that induced flavor-changing Yukawa couplings are extremely small.