Structure Of Quark Mass Matrices Research Articles

Minimizing the phase structure of quark mass matrices

Fritzsch–Xing matrices are a particular class of texture 4 zero hermitian quark mass matrices, known to be successful in accommodating the quark mixing data. In the present work, it is shown that these texture 4-zero matrices with only one phase parameter, unlike the usually considered two phase parameters, are not only consistent with the latest experimental quark mixing data, but also predict the CP violation parameters, J and corresponding phase delta , in agreement with the recent global analyses. We also show that the mass matrix elements do not exhibit a strong hierarchy and there is a strong correlation between some of the mass matrix elements of up and down sector. A precision measurement of delta as well as small quark masses would have the potential to constrain the phase structure of the matrices further.

QUARK MASS MATRICES AND OBSERVABLE QUANTITIES

A nearly historical account of quark mass matrix models is given, and the structure of quark mass matrices in the standard model is studied. For a minimal parameter basis suggested earlier, where Mu is diagonal and Md11, Md13, Md31 are zero, the dependence of mass matrices on the CP violating phase δ of V CKM is reported: all parameters are almost independent, except Md22 and Md23, and the equality |Md22| = Md23 is obtained for a value of δ very close to the value which is favored by experiments. Moreover, on this basis, Md12≃Md21 and Md33≃2Md32. Some comments on mass matrices in left–right symmetric models are added.

Patterns of quark mass matrices in a class of Calabi-Yau models

We study a class of superstring models compactified in the 3-generation Calabi-Yau manifold of Tian and Yau. Our analysis includes the complete E 6-singlet sector, which has been recently evaluated using techniques of spectral and exact sequences. We use the discrete symmetries of the models to find flat directions of symmetry breaking that leave unbroken a low energy matter parity and make all leptoquarks heavy while preserving light Higgs fields. Then we classify the patterns of ordinary quark mass matrices and show that (without invoking effects due to nonrenormalizable terms) only one structure can accommodate the observed value of fermion masses and mixing angles. The model, which unifies perturbatively and predicts a realistic structure of quark mass matrices with texture zeros, is one of the many possible string vacua. However, in contrast with what is often assumed in the search for realistic unified scenarios, it is highly nonminimal near the unification scale, and the predicted mass matrices have no simple symmetry properties.

CP violation, horizontal symmetry and the Kobayashi-Maskawa matrix

It is pointed out that in order to have CP violation in horizontal, generation mixing, interactions, while the Kobayashi-Maskawa matrix itself is real, a very specific structure is required for the unitary matrices that relate weak to mass eigenstates. Implications for the structure of quark mass matrices are also discussed.

Structure of quark mass matrices in the rishon model

Consequence of a proposed horizontal symmetry Z 12 for the structure of quark mass matrices in the rishon model are investigated. A single model with both a definite prediction for the Cabibbo angle and a natural explanation for the magnitude of CP violation is found.

Quark mass matrices in left-right symmetric gauge theories

The most general left-right symmetry for SU(2) L×SU(2) R×U(1) gauge theories with any number of flavours and with at most two scalar multiplets transforming as q q bilinears is analyzed. In order to get additional constraints on the structure of quark mass matrices, all possible horizontal groups (continuous or discrete) are investigated. We give a complete classification of physically inequivalent quark mass matrices for four and six flavours. It is argued that our methods and results are also applicable in the case of dynamical symmetry breaking. Parity invariance and horizontal symmetry are shown to imply CP conservation on the lagrangian level. For all non-trivial three-generation models there is spontaneous CP violation, which in most cases turns out to be naturally small. Several six-flavour models predict m t ≅m b ( m u m c m d m s ) 1 2 and are, therefore, already ruled out experimentally. In the remaining few realistic models, predictions for the weak mixing angles are made.