12359775
Covariant, chirally symmetric, confining model of mesons.
We introduce a new model of mesons as quark-antiquark bound states. The model is covariant, confining, and chirally symmetric. Our equations give an analytic solution for a zero-mass pseudoscalar bound state in the case of exact chiral symmetry, and also reduce to the familiar, highly successful nonrelativistic linear potential models in the limit of heavy-quark mass and lightly bound systems. In this fashion we are constructing a unified description of all the mesons from the {pi} through the {Upsilon}. Numerical solutions for other cases are also presented.
125805875
HADRONIC DECAYS OF LOW LYING GLUEBALLS
118254960
Relativistic theory of few body systems and their electromagnetic interactions
Recent results obtained from the manifestly covariant spectator theory are summarized. A recent unpublished best fit to NN scattering using 13 OBE parameters gives x{sup 2}=2.25 and a triton binding energy of {minus}8.491 MeV. This agreement is possible because of the existence of off-shell coupling of the phenomenological, intermediate range effective scalar exchanges (both isoscalar and isovector). The previously published results for the deuteron form factors are reviewed, and new, preliminary results for electrodisintegration of the deuteron are presented.
118704383
Nucleon and N‐Delta Electromagnetic Transition Form Factors
We consider the baryons as three constituent valence quark systems. Their dynamics is described by the covariant Spectator formalism [1,2] for a quark-diquark system, where the diquark is always on its mass-shell. The electromagnetic interaction is considered in the relativistic impulse interaction (RIA) where the photon couples with the quark through the current j M = j\y^ + 72 l°2mV (m *s ^ e n u c l e o n mass). The two form factors j'l and 72 account for all QCD mechanisms (qq pairs, pion cloud and gluon sea effects). Only the 71 form factor includes pion cloud effects in its isovector part. The nucleon wave function consists of spin-0 (isospin-0) and spin-1 (isospin-l) components written in terms of the diquark polarization vectors and the nucleon Dirac spinor [1]. Furthermore, it verifies the Dirac equation and generates the correct structure for its non-relativistic limit. Current conservation is also satisfied. The Jlab polarization data of the electromagnetic nucleon elastic form factors are described [3,4] when one assumes an S-state for the quark-diquark system [1], which means that the data does not signal any angular dependence in the wave function. The results show that spherical charge and matter distributions aremore » compatible with the data, even when we consider Spin Direction Dependent density definitions [5]. The explicit consideration of the pion cloud effects definitively improves the description of the nucleon form factors [1]. We also calculated the N-Delta transition form factors. Preliminary results considering the Delta wave function as a mixture of a S and a D state explain the magnetic dipole G*M and the electric quadrupole G*E data [6]. Improvements are underway in order to describe also the Coulomb quadrupole form factor G£« less
119626591
Relativistic effects in few nucleon systems
Abstract The discussion session on relativistic effects was moderated by Professor Walter Glockle, of the Universitat Bochum. This report is divided into two main sections on (1) relativistic few body equations and (2) relativistic calculations of matrix elements. In some places the discussion is incorporated into the text, but a number of issues pertaining to the first topic are summarized separately in part 1.3.
125810230
Complete measurements of scalar and pseudoscalar electroproduction
32193057
High-energy symmetries of string theory.
By means of a recent analysis of the high-energy limit of string scattering, linear relations between string scattering amplitudes are derived. These are shown to hold order by order in perturbation theory. If one assumes that they hold for the full theory, they suggest the existence of an enormous string-broken symmetry which is restored at high energies. Some speculations as to the nature of this symmetry are presented.