3,946 research outputs found
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
Experimental Tests of Non-Perturbative Pion Wave Functions
We use the transverse-momentum dependence of the cross section for
diffractive dissociation of high energy pions to two jets to study some
non-perturbative Light-Cone wave functions of the pion. We compare the
predictions for this distribution by Gaussian and Coulomb wave functions as
well as the wave function derived from solution of the Light-Cone Hamiltonian
in the Singlet Model. We conclude that this experimentally measured information
provides a powerful tool for these studies.Comment: 5 pages, 4 figure
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
On the Size of Hadrons
The form factor and the mean-square radius of the pion are calculated
analytically from a parametrized form of a wave function. The
numerical wave function was obtained previously by solving numerically an
eigenvalue equation for the pion in a particular model. The analytical formulas
are of more general interest than just be valid for the pion and can be
generalized to the case with unequal quark masses. Two different
parametrizations are investigated. Because of the highly relativistic problem,
noticable deviations from a non-relativistic formula are obtained.Comment: 14 pages, minor typos corrected, several points clarified, results
unchange
Project Tektite 1 - A multiagency 60 day saturated dive conducted by the United States Navy, the National Aeronautics and Space Administration, the Department of the Interior, and the General Electric Company Summary report
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A Lorentz-Violating Alternative to Higgs Mechanism?
We consider a four-dimensional field-theory model with two massless fermions,
coupled to an Abelian vector field without flavour mixing, and to another
Abelian vector field with flavour mixing. Both Abelian vectors have a
Lorentz-violating kinetic term, introducing a Lorentz-violation mass scale ,
from which fermions and the flavour-mixing vector get their dynamical masses,
whereas the vector coupled without flavour mixing remains massless. When the
two coupling constants have similar values in order of magnitude, a mass
hierarchy pattern emerges, in which one fermion is very light compared to the
other, whilst the vector mass is larger than the mass of the heavy fermion. The
work presented here may be considered as a Lorentz-symmetry-Violating
alternative to the Higgs mechanism, in the sense that no scalar particle
(fundamental or composite) is necessary for the generation of the vector-meson
mass. However, the model is not realistic given that, as a result of Lorentz
Violation, the maximal (light-cone) speed seen by the fermions is smaller than
that of the massless gauge boson (which equals the speed of light in vacuo) by
an amount which is unacceptably large to be compatible with the current tests
of Lorentz Invariance, unless the gauge couplings assume unnaturally small
values. Possible ways out of this phenomenological drawback are briefly
discussed, postponing a detailed construction of more realistic models for
future work.Comment: 16 pages revtex, three eps figures incorporate
Discretized light-cone quantization and the effective interaction in hadrons
Light-cone quantization of gauge theories is discussed from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and as a novel method for simulating quantum field theory on a computer. A general non-perturbative method for numerically solving quantum field theories, `discretized light-cone quantization', is outlined. Both the bound-state spectrum and the corresponding relativistic wavefunctions can be obtained by matrix diagonalization and related techniques. Emphasis is put on the construction of the light-cone Fock basis and on how to reduce the many-body problem to an effective Hamiltonian. The usual divergences are avoided by cut-offs and subsequently removed by the renormalization group. For the first time, this programme is carried out within a Hamiltonian approach, from the beginning to the end. Starting with the QCD-Lagrangian, a regularized effective interaction is derived and renormalized, ending up with an almost solvable integral equation.Its eigenvalues yield the mass spectrum of physical mesons, its eigenfunctions yield their wavefunctions including the higher Fock-space components. An approximate but analytic mass formula is derived for all physical mesons
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