2,140 research outputs found
Quantum Chromodynamics and Other Field Theories on the Light Cone
We discuss the light-cone quantization of gauge theories as a calculational
tool for representing hadrons as QCD bound-states of relativistic quarks and
gluons, and also as a novel method for simulating quantum field theory on a
computer. The light-cone Fock state expansion of wavefunctions provides a
precise definition of the parton model and a general calculus for hadronic
matrix elements. We present several new applications of light-cone Fock
methods, including calculations of exclusive weak decays of heavy hadrons, and
intrinsic heavy-quark contributions to structure functions. Discretized
light-cone quantization, is outlined and applied to several gauge theories. We
also discuss the construction of the light-cone Fock basis, the structure of
the light-cone vacuum, and outline the renormalization techniques required for
solving gauge theories within the Hamiltonian formalism on the light cone.Comment: 206 pages Latex, figures included, Submitted to Physics Report
Renormalization of an effective Light-Cone QCD-inspired theory for the Pion and other Mesons
The renormalization of the effective QCD-Hamiltonian theory for the
quark-antiquark channel is performed in terms of a renormalized or fixed-point
Hamiltonian that leads to subtracted dynamical equations. The fixed
point-Hamiltonian brings the renormalization conditions as well as the
counterterms that render the theory finite. The approach is renormalization
group invariant. The parameters of the renormalized effective QCD-Hamiltonian
comes from the pion mass and radius, for a given constituent quark mass. The 1s
and excited 2s states of are calculated as a function of the mass of
the quark being s, c or b, and compared to the experimental values.Comment: 39 pages, 10 figure
Tube Model for Light-Front QCD
We propose the tube model as a first step in solving the bound state problem
in light-front QCD. In this approach we neglect transverse variations of the
fields, producing a model with 1+1 dimensional dynamics. We then solve the two,
three, and four particle sectors of the model for the case of pure glue SU(3).
We study convergence to the continuum limit and various properties of the
spectrum.Comment: 29 page
Universal description of S-wave meson spectra in a renormalized light-cone QCD-inspired model
A light-cone QCD-inspired model, with the mass squared operator consisting of
a harmonic oscillator potential as confinement and a Dirac-delta interaction,
is used to study the S-wave meson spectra. The two parameters of the harmonic
potential and quark masses are fixed by masses of rho(770), rho(1450), J/psi,
psi(2S), K*(892) and B*. We apply a renormalization method to define the model,
in which the pseudo-scalar ground state mass fixes the renormalized strength of
the Dirac-delta interaction. The model presents an universal and satisfactory
description of both singlet and triplet states of S-wave mesons and the
corresponding radial excitations.Comment: RevTeX, 17 pages, 7 eps figures, to be published in Phys. Rev.
Masses of the physical mesons from an effective QCD--Hamiltonian
The front form Hamiltonian for quantum chromodynamics, reduced to an
effective Hamiltonian acting only in the space, is solved
approximately. After coordinate transformation to usual momentum space and
Fourier transformation to configuration space a second order differential
equation is derived. This retarded Schr\"odinger equation is solved by
variational methods and semi-analytical expressions for the masses of all 30
pseudoscalar and vector mesons are derived. In view of the direct relation to
quantum chromdynamics without free parameter, the agreement with experiment is
remarkable, but the approximation scheme is not adequate for the mesons with
one up or down quark. The crucial point is the use of a running coupling
constant , in a manner similar but not equal to the one of
Richardson in the equal usual-time quantization. Its value is fixed at the Z
mass and the 5 flavor quark masses are determined by a fit to the vector meson
quarkonia.Comment: 18 pages, 4 Postscript figure
Gluon Distribution Functions for Very Large Nuclei at Small Transverse Momentum
We show that the gluon distribution function for very large nuclei may be
computed for small transverse momentum as correlation functions of an
ultraviolet finite two dimensional Euclidean field theory. This computation is
valid to all orders in the density of partons per unit area, but to lowest
order in . The gluon distribution function is proportional to ,
and the effect of the finite density of partons is to modify the dependence on
transverse momentum for small transverse momentum.Comment: TPI--MINN--93--52/T, NUC--MINN--93--28/T, UMN--TH--1224/93, LaTex, 11
page
Finiteness Conditions for Light-Front Hamiltonians
In the context of simple models, it is shown that demanding finiteness for
physical masses with respect to a longitudinal cutoff, can be used to fix the
ambiguity in the renormalization of fermions masses in the Hamiltonian
light-front formulation. Difficulties that arise in applications of finiteness
conditions to discrete light-cone quantization are discussed.Comment: REVTEX, 9 page
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