Fermion Masses and Mixing in Four and More Dimensions

Abstract

We give an overview of recent progress in the study of fermion mass and flavor mixing phenomena. Mass matrix ansatze are considered within the SM and SUSY GUTs where some predictive frameworks based on SU(5) and SO(10) are reviewed. We describe a variety of schemes to construct quark mass matrices in extra dimensions focusing on four major classes: models with the SM residing on 3-brane, models with universal extra dimensions, models with split fermions and models with warped extra dimensions. We outline how realistic patterns of quark mass matrices could be derived from orbifold models in heterotic superstring theory. Finally, we address the fermion mass problem in intersecting D-branes scenarios, and present models with D6-branes able to give a good quantitatively description of quark masses and mixing. The role of flavor/CP violation problem as a probe of new physics is emphasized.

Pieces of the flavour puzzle

“…The construction relies on a spontaneously broken abelian flavour symmetry, but the final results (6)(7)(8)(9) are valid in a more general context, where no symmetry is present to start with. A simple example is provided by a model with an extra spatial dimension, compactified on an orbifold S 1 /Z 2 to allow for 4D chiral fermions.…”

“…Several aspects that have been left aside or only briefly mentioned in this paper are covered in a number of reviews [ 1 – 4 ]. In particular I will not do justice to the vast literature of fermion masses in grand unified theory [ 5 – 7 ], nor to that discussing the flavour puzzle in the framework of string theory [ 8 , 9 ].…”