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

The Size of the Weak Bosons

We study the hypothesis that weak bosons are composite systems, which have a size of the order of 10^{-17} cm. The electromagnetic selfenergies of the weak bosons lead to specific departures from the standard electroweak model, in agreement with observation. Above the energy of 1 TeV the standard electroweak model breaks down completely.Comment: 8 page

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

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

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

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

How to Describe Neutrino Mixing and CP Violation

We present a classification of possible parametrizations of the 3x3 lepton flavor mixing matrix in terms of the rotation and phase angles. A particular parametrization, which is most convenient to describe the observables of neutrino oscillations and that of the neutrinoless double beta decay, is studied in detail. The possibility to determine the Dirac- and Majorana-type CP-violating phases are also discussed.Comment: Latex 9 pages. Some changes. Phys. Lett. B in printin

Four-Zero Texture of Hermitian Quark Mass Matrices and Current Experimental Tests

We show that the four-zero texture of Hermitian quark mass matrices can survive current experimental tests: it is able to yield sufficiently large predictions for the flavor mixing parameter $|V_{ub}/V_{cb}|$ and the CP-violating parameter $\sin 2\beta$, without fine-tuning of the input values of quark masses, provided the (2,2), (2,3) and (3,3) elements of up and down mass matrices roughly satisfy a geometrical hierarchy. The successful relations $|V_{us}| \approx \sqrt{m_u/m_c + m_d/m_s}$ and $|V_{td}/V_{ts}| \approx \sqrt{m_d/m_s}$ obtained previously from the six-zero texture of Hermitian quark mass matrices remain unchanged in the new ansatz.Comment: LaTex 9 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

Maximal CP Violation Hypothesis and Phase Convention of the CKM Matrix

The maximal CP violation hypothesis depends on the phase convention of the Cabibbo-Kobayashi-Maskawa matrix. A phase convention which leads to successful prediction under the maximal CP violation hypothesis is searched, and thereby, possible structures of the quark mass matrices are speculated.Comment: 9 pages, no figure, references adde