SUSY GUT model building

The evolution of SUSY GUT model building is discussed, starting with the construction of 4D GUTs, to orbifold GUTs and finally to orbifold GUTs, within the heterotic string model. This evolution is an attempt to obtain realistic string models, perhaps relevant for the LHC. This review is in memory of the sudden loss of Julius Wess, a leader in the field, who will be sorely missed. Dedicated to the memory of Julius Wess.     

QCD and a holographic model of hadrons

We propose a five-dimensional framework for modeling low-energy properties of QCD. In the simplest three parameter model we compute masses, decay rates and couplings of the lightest mesons. The model fits experimental data to within 10%. The framework is a holographic version of the QCD sum rules, motivated by the anti-de Sitter/conformal field theory correspondence. The model naturally incorporates properties of QCD dictated by chiral symmetry, which we demonstrate by deriving the Gell-Mann-Oakes-Renner relationship for the pion mass.     

R-parity violating SUSY model

This is a phenomenological review ofR parity violating SUSY models, with particular emphasis on explicitR parity violation.     

The case for a quartet model of hadrons

A model of hadrons based on an underlying quartet leads to a more satisfactory picture of weak interactions than one based on a triplet. Hadrons containing the fourth type of quark may be as low as 700 MeV above their uncharmed counterparts. It is argued that charmed hadrons should be searched for in photoproduction and (under certain circumstances) in hadronic formation experiments.     

Spontaneous CP violation in a SUSY model with a complex CKM

It is pointed out that the recent measurement of the angle γ   of the unitarity triangle, providing irrefutable evidence for a complex Cabibbo–Kobayashi–Maskawa (CKM) matrix, presents a great challenge for supersymmetric models with spontaneous CP violation. We construct a new minimal extension of the minimal supersymmetric standard model (MSSM), with spontaneous CP breaking, which leads to a complex CKM matrix, thus conforming to present experimental data. This is achieved through the introduction of two singlet chiral superfields and a vector-like quark chiral superfield which mixes with the standard quarks. A Z₃$Z_3$ symmetry is introduced in order to have a potential solution to the strong CP problem.     

SUSY CP problem in gauge mediation model

SUSY CP problem in the gauge mediation supersymmetry breaking model is reconsidered. We pay particular attention to two sources of CP violating phases whose effects were not seriously studied before; one is the effect of the breaking of the GUT relation among the gaugino masses due to the field responsible for the GUT symmetry breaking, and the other is the supergravity effect on the supersymmetry breaking parameters, in particular, on the bi-linear supersymmetry breaking Higgs mass term. We show that both of them can induce too large electric dipole moments of electron, neutron, and so on, to be consistent with the experimental bounds.     

Study of heavy-light hadrons within a flux tube model

A classic mass loaded flux tube model and the diquark picture are employed to explore both mesons and baryons. The spectrum of Λ_c⁺ baryons and D_s mesons is systematically obtained. The spin-orbit interaction in D_s was simplified as an L·S coupling. The spin-orbit interaction in Λ_c was simplified as a J_l·J_c coupling. The predicted masses are consistent with the latest experiments.     

Study of heavy-light hadrons within a flux tube model

A classic mass loaded flux tube model and the diquark picture are employed to explore both mesons and baryons. The spectrum of A<'+><,c> baryons and D<,s> mesons is systematically obtained. The spin-orbit interaction in Ds was simplified as and (L→·S→) coupling.The spin-orbit interaction in Ac was simplified as a (J1→·Jc→) coupling. The predicted masses are consistent with the latest experiments.     

A Markoffian model for hadrons

The hadron is considered as a system consisting of other bound hadrons, the configuration state of which changes with the time. Its time development is described as a Markov process by Kolmogorov's equations. The stationary solution of Kolmogorov's equations for the Markoffian hadronic system makes it possible to calculate certain physical parameters for stable hadrons. The calculation of the magnetic moments of the proton and neutron in this model yields values which are in good agreement with the experimental data.     

Selection rules in a unified gauge model of leptons and hadrons

Decay modes and lifetimes of quarks, vector mesons and protons are determined for the unified model of leptons and hadrons recently proposed by Pati and Salam. It is found that while both the quarks and gauge mesons decay too rapidly to be observed, protons will be comfortably stable against decay into leptons, consistent with earlier estimates and existing experimental evidence. It is of special interest that while quarks may not be directly observable, their presence may be verified owing to the uniqueness of their preferred decay into quite a large number of pions. We also discuss an anomalous lepton-hadron scattering process whose occurrence would imply the presence of exotic SU(4) gluons carrying both baryon and lepton number.     

A non-Abelian vortex-bond model of hadrons

It is argued for a general class of models by analyzing the internal holonomy group of the cylindrically symmetric solutions that the most general vortex-like configurations of minimal energy can always be transformed to Abelian form. The corresponding “magnetic” fluxes are defined gauge invariantly. In the case of the SU(3) local gauge group, Nambu's valency-model is recovered. The stability problem in the case of small-amplitude oscillations reduces to the analogue investigation for “truly” Abelian vortices.     

Masses ofq 2 \bar q 2 states in a Bethe-Salpeter model

Ground-state masses ofq ^{2 –2} states (true and mock baryonium) are investigated in the framework of a Bethe-Salpeter formalism motivated from QCD. The four-particle system is described by pairwise interactions betweenqq orq pairs with a spectator approximation for the non-interacting pair. The quark-quark interactions are Coulomb plus harmonic interactions; the harmonic terms have been modified to produce linear confinement for heavier quarks, in agreement with experimental spectra. The confining interaction is proportional to the strong coupling constant _s. Apart from the quark masses, the confining interaction is characterized by three basic parameters: (i) a universal spring constant ₀; (ii) a constantC ₀/ ₀ ² , which defines the vacuum structure; (iii) a constantA ₀, which provides a smooth transition from quadratic to linear confinement as one goes from light to heavy quark systems. These three constants [ ₀ = 0.158 GeV;C ₀=0.296;A ₀=0.0283] have been shown to produce excellent fits to all quarkonia states [q ,q ,Q ] as well as baryon spectra (qqq); thus our predictions forq ^{2 2} states contain no free parameters. In this model, theL=0 ground states occur in the range 1.8–2 GeV, 2.15–2.3 GeV and 6.72–6.75 GeV foru ^{2 2},s ^{2 2} andc ^{2 2} states, respectively. We discuss the prospects for these states to be seen experimentally. In the case of thes ^{2 2} state, this is likely to have a rather narrow width, and may correspond to theX(2.22 GeV) meson observed in radiative decays of theJ/ meson. Thec ^{2 2} state might also be visible as a resonance with an appreciable width.Research supported in part by the National Science Foundation under grant NSF-PHY 86-06364Research supported in part by the U.S. Department of Energy     

The generalized parton distribution of the pion in a relativistic Bethe-Salpeter quark model

We present a Poincaré covariant calculation of the generalized parton distribution of the pion. Results for different values of the kinematical parameters are shown and discussed.     

The nuclear force and a magnetic monopole model of hadrons

The two-pion exchange potential of the nuclear force is constructed from the phase shifts of the low energy πN and ππ scattering. The large difference between the potentials thus constructed from the phenomenological potentials of Hamada-Johnston and of Bryan is pointed out. It is found that this difference has the form of the attractive Van der Waals potential plus an inner repulsive core. The existence of the Van der Waals force is discussed in connection with the magnetic monopole model of hadrons.     

A new quark model for hadrons

It is suggested that quarks and leptons are composites of still more fundamental PRE-entities.