Flavorspin

TL;DR

This paper introduces Flavorspin, a novel SU(2) flavor symmetry model for quark flavor structure, where Yukawa couplings are real, CP violation arises separately, and the symmetry scale suppresses flavor-changing processes.

Contribution

It proposes a new SU(2) flavor symmetry framework with real Yukawa couplings, decoupling CP violation from flavor symmetry breaking, and explores its implications for quark masses, mixings, and CP violation.

Findings

Yukawa couplings are real and determined by masses and mixings.

CP violation can be introduced with minimal impact on low-energy observables.

Flavor-changing neutral currents are suppressed by a high symmetry-breaking scale.

Abstract

We propose that the flavor structure of the quark sector of the Standard Model is determined by a vectorial SU(2) flavor symmetry, which we dub Flavorspin, under which quarks transform as triplets. The fundamental Yukawa couplings are real and CP violation is not directly linked to the breaking of the flavor symmetry. A CP-conserving scenario is naturally defined with the feature that the Yukawa spurions are completely determined in terms of the masses and mixings. CP violation may be introduced with negligible impact on low-energy observables other than generating a large CP violating phase in the Standard Model mixing matrix. The scale of flavor-symmetry violation must be large in order to prevent sizable Flavor Changing Neutral Currents, which can be partially suppressed if Flavorspin is a residual symmetry of a larger flavor group.