37 research outputs found
Wavefunction-Independent Relations between the Nucleon Axial-Coupling g_A and the Nucleon Magnetic Moments
We calculate the proton's magnetic moment and its axial-vector
coupling as a function of its Dirac radius using a relativisitic
three-quark model formulated on the light-cone. The relationship between
and is found to be independent of the assumed form of the
light-cone wavefunction. At the physical radius fm, one obtains the
experimental values for both and , and the helicity carried by the
valence and quarks are each reduced by a factor relative
to their non-relativistic values. At large proton radius, and are
given by the usual non-relativistic formulae. At small radius, becomes
equal to the Dirac moment, as demanded by the Drell-Hearn-Gerasimov sum rule.
In addition, as the constituent quark helicities become completely
disoriented and .Comment: 17 pages, RevTeX, 4 uuencoded figures, SLAC-PUB-643
Magnetic Moments of the Baryon Decuplet in a Relativistic Quark Model
The magnetic moments of the baryon decuplet are calculated in a relativistic
constituent quark model using the light-front formalism. Of particular interest
are the magnetic moments of the and for which new
recent experimental measurements are available. Our calculation for the
magnetic moment ratio is in excellent agreement with
the experimental ratio, while our ratio is
slightly higher than the experimental ratio.Comment: 10 pages ReVTeX, SLAC-PUB-621
RELATIVISTIC CORRECTIONS TO THE ELECTROMAGNETIC AND AXIAL MOMENTS OF NUCLEI AND OTHER COMPOSITE SYSTEMS
We calculate the electromagnetic and axial nuclear moments of the deuteron
and triton as a function of their radius using a relativistic two-nucleon and
three-nucleon model formulated on the light-cone. The results also provide an
estimate of the nuclear binding corrections to helicity-dependent deep
inelastic scattering sum rules. At large nucleon radius, the moments are given
by the usual non-relativistic formulae modified by finite binding effects. At
small radius, the moments take the canonical values given by the generalization
of the Drell-Hearn-Gerasimov sum rule. In addition, as R-->0, the constituent
helicities become completely disoriented, and the Gamow-Teller matrix element
vanishes. Thus, in the pointlike limit MR-->0, the moments of a spin-one bound
states coincide with the canonical couplings of elementary spin-one bosons of
the Standard Model, mu=e/M, Q=-e/M^2, and g_A=0.Comment: 10 pages, uuencoded postscript file. To obtain a copy of this paper,
send e-mail to [email protected] and ask for i
Beta decay of hyperons in a relativistic quark model
A relativistic constituent quark model is used to calculate the semileptonic
beta decay of nucleons and hyperons. The parameters of the model, namely, the
constituent quark mass and the confinement scale, are fixed by a previous
calculation of the magnetic moments of the baryon octet within the same model.
We discuss the momentum dependence of the form factors, possible configuration
mixing and SU(3) symmetry breaking. We conclude that the relativistic
constituent quark model is a good framework to analyze electroweak properties
of the baryons.Comment: RevTeX, 14 pages, SLAC-PUB-666
The Role of Color Neutrality in Nuclear Physics--Modifications of Nucleonic Wave Functions
The influence of the nuclear medium upon the internal structure of a
composite nucleon is examined. The interaction with the medium is assumed to
depend on the relative distances between the quarks in the nucleon consistent
with the notion of color neutrality, and to be proportional to the nucleon
density. In the resulting description the nucleon in matter is a superposition
of the ground state (free nucleon) and radial excitations. The effects of the
nuclear medium on the electromagnetic and weak nucleon form factors, and the
nucleon structure function are computed using a light-front constituent quark
model. Further experimental consequences are examined by considering the
electromagnetic nuclear response functions. The effects of color neutrality
supply small but significant corrections to predictions of observables.Comment: 37 pages, postscript figures available on request to
[email protected]