The Production of Single t-Quarks at LEP and HERA

We study the possibility to produce single t-quarks both at LEP II and HERA. While within the Standard Model such reactions are not observable, the possibility exists in a wide class of dynamical models for the fermion mass generation. General arguments, based on hierarchical and democratic symmetries are used to arrive at t-production rates which are detectable.Comment: 10 latex page

Lepton Mass Hierarchy and Neutrino Mixing

We speculate that the mass spectrum of three neutrinos might have a normal hierarchy as that of three charged leptons or that of three up-type (or down-type) quarks. In this spirit, we propose a novel parametrization of the $3\times 3$ lepton flavor mixing matrix. Its mixing angles $\theta_l$ and $\theta_\nu$ can be related to the mass ratios $m_e/m_\mu$ and $m_1/m_2$ in a specific texture of lepton mass matrices with vanishing (1,1) elements: $\tan\theta_l = \sqrt{m_e/m_\mu}$ and $\tan\theta_\nu = \sqrt{m_1/m_2}$. The latter relation, together with solar and atmospheric neutrino oscillation data, predicts 0.0030 eV $\lesssim m_1 \lesssim$ 0.0073 eV, 0.009 eV $\lesssim m_2 \lesssim$ 0.012 eV and 0.042 eV $\lesssim m_3 \lesssim$ 0.058 eV. The smallest neutrino mixing angle is found to be $\theta_{13} \approx \theta_l/\sqrt{2} \approx 3^\circ$, which is experimentally accessible in the near future.Comment: RevTex 10 pages, 2 figure

Relating the neutrino mixing angles to a lepton mass hierarchy

We propose two phenomenological scenarios of lepton mass matrices and show that either of them can exactly give rise to \tan^2\theta_{13} = m_e/(m_e + 2m_\mu), \tan^2\theta_{23} = m_\mu/(m_e + m_\mu) and \tan^2\theta_{12} = (m_e m_2 + 2m_\mu m_1)/(m_e m_1 + 2m_\mu m_2) in the standard parametrization of lepton flavor mixing. The third relation, together with current experimental data, predicts a normal but weak hierarchy for the neutrino mass spectrum. We also obtain \theta_{13} \approx 2.8^\circ for the smallest neutrino mixing angle and J \approx 1.1% for the Jarlskog invariant of leptonic CP violation, which will soon be tested in the long-baseline reactor and accelerator neutrino oscillation experiments. A seesaw realization of both scenarios is briefly discussed.Comment: RevTeX 11 pages. Accepted for publicatio

The Spin Structure of the Constituent Quarks and of the Nucleon

We define a constituent quark within QCD. It is shown that the spin of such a quark and hence also the spin of the nucleon reduced due to $\bar{q}q$-pairs, in agreement with experiment. A solution to the spin problem is given.Comment: 7 page

The Light Quark Sector, CP Violation, and the Unitarity Triangle

In view of the observed strong hierarchy of quark masses, we propose a new description of flavor mixing which is particularly suited for models of quark mass matrices based on flavor symmetries. The necessary and sufficient conditions for CP violation are clarified. The emergence of CP violation is primarily linked to a large phase difference (near 90^{\circ}) in the light quark sector. The unitarity triangle is determined by the mass ratios of the light quarks. We conclude that the unitarity triangle should be close or identical to a rectangular triangle, and CP violation is maximal in this sense. Instructive predictions for flavor mixing angles and CP-violating parameters, which can directly be confronted with the forthcoming data from B-meson factories, are obtained from a specific texture of quark mass matrices.Comment: Latex 28 pages. Nucl. Phys. B (in printing

Nearly Tri-Bimaximal Neutrino Mixing and CP Violation

We point out two simple but instructive possibilities to modify the tri-bimaximal neutrino mixing ansatz, such that leptonic CP violation can naturally be incorporated into the resultant scenarios of nearly tri-bimaximal flavor mixing. The consequences of two new ansaetze on solar, atmospheric and reactor neutrino oscillations are analyzed. We also discuss an interesting approach to construct lepton mass matrices under permutation symmetry, from which one may derive another nearly tri-bimaximal neutrino mixing scenario with no intrinsic CP violation in neutrino oscillations.Comment: LaTex 10 pages. Phys. Lett. B (in press

Quark Mass Hierarchies, Flavor Mixing and Maximal CP-Violation

Flavor mixing and the quark mass spectrum are intimately related. In view of the observed strong hierarchy of the quark and lepton masses and of the flavor mixing angles it is argued that the description of flavor mixing must take this into account. One particular interesting way to describe the flavor mixing emerges, which is particularly suited for models of quark mass matrices based on flavor symmetries. We conclude that the unitarity triangle important for $B$ physics should be close to or identical to a rectangular triangle. $CP$ violation is maximal in this sense.Comment: 21 latex page

Isospin Symmetry Breaking and the ρ−ω\rho-\omega-System

Simple quark models for the low lying vector mesons suggest a mixing between the u- and d-flavors and a violation of the isospin symmetry for the $\rho-\omega$- system much stronger than observed. It is shown that the chiral dynamics, especially the QCD anomaly, is responsible for a restoration of the isospin symmetry in the $\rho-\omega$-system.Comment: 4 pages, espcrc2.st

Large Mixing and CP Violation in Neutrino Oscillations

I introduce a simple phenomenological model of lepton flavor mixing and CP violation based on the flavor democracy of charged leptons and the mass degeneracy of neutrinos. The nearly bi-maximal mixing pattern, which can interpret current data on atmospheric and solar neutrino oscillations, emerges naturally from this model. The rephasing-invariant strength of CP or T violation amounts to about one percent and could be measured in the long-baseline neutrino experiments. The similarity and difference between lepton and quark flavor mixing phenomena are also discussed.Comment: LaTex 6 pages. Talk given at the Sixth Topical Seminar on Neutrino and Astroparticle Physics, San Miniato, Italy, May 1999 (To appear in the Proceedings Supplements of Nucl. Phys. B