Flavor symmetries and fermion masses

Abstract

We introduce several ways in which approximate flavor symmetries act on fermions and which are consistent with observed fermion masses and mixings. Flavor changing interactions mediated by new scalars appear as a consequence of approximate flavor symmetries. We discuss the experimental limits on masses of the new scalars, and show that the masses can easily be of the order of weak scale. Some implications for neutrino physics are also discussed. , Such flavor changing interactions would easily erase any primordial baryon asymmetry. We show that this situation can be saved by simply adding a new charged particle with its own asymmetry. The neutrality of the Universe, together with sphaleron processes, then ensures a survival of baryon asymmetry.Several topics on flavor structure of the supersymmetric grand unified theories are discussed. First, we show that the successful predictions for the Kobayashi-Maskawa mixing matrix elements, Vu&/Vcb = 1 Jm.,Jmc and "Vtd/Vts Jmd/m 8 , are a consequence of a large class of models, rather than specific properties of a few models. Second, we discuss how the recent observation of the decay b -+ S/ constrains the parameter space when the ratio of the vacuum expectation values of the two Higgs doublets, tan/3, is large. Finally, we discuss the flavor structure of proton decay. We observe a surprising enhancement of the branching ratio for the muon mode in S0(10) models compared to the same mode in the SU(5) model.

Texture zeros and weak basis transformations in the quark sector of the standard model

“…It is usually said that the CKM matrix is an arbitrary unitary matrix with five phases rotated away through the phase redefinition of the left-handed up and down quark fields [13]. This can be shown by using the following unitary matrix (2.17)…”

“…The expression into the square brackets is precisely the most general way to write a unitary matrix [13].…”

The light quark sector, CP violation, and the unitarity triangle

“…Since the concrete calculation of those mixing angles from R u,d 12 , R u,d 23 and R u,d 31 is rather complicated and less instructive (see, e.g., Ref. [27]), we shall subsequently follow a different and more straightforward procedure towards the same goal.…”

Parametrizing the Mixing Matrix: A Unified Approach

“…After the pioneering work of Kobayashi and Maskawa, 1 this matrix, which describes the mixing between quark mass eigenstates and the charged weak current eigenstates, has been parametrized in a number of phenomenologically useful ways. [2][3][4][5][6][7][8] Generalizations to N ≥ 3 generations of quarks, where the mixing matrix is characterized by N (N −1)/2 angles and (N −1)(N −2)/2 phases, have also been proposed. [8][9][10][11][12][13][14][15][16] Analogs of the mixing matrix also arise in the lepton sector if the neutrinos are taken as massive Dirac particles.…”