Light Front Cloudy Bag Model
Gerald A. Miller
The light front version of the cloudy bag model is now under
construction. The model consists of a relativistic
system of three bound quarks interacting with a pion cloud.
Light front dynamics is used so that the boosts can be treated as kinematic.
The quark aspects of the model are given at
This model can not account for the neutron electromagnetic
form factors using only quarks. The light front cloudy bag model
is defined by including the effects of a pion cloud along with the
quarks. As in the original cloudy bag model, the pion effects are a
perturbative correction. References to the original cloudy bag model
are given at
The present work can be thought of as a relativistic version of the
the original cloudy bag model. The photon can interact with the bare
nucleon, or a pion in flight, or a nucleon while there is a pion in flight.
I have not yet written up this work, but I want to make the numerical
results available now. Before listing the figures,
let me explain the parameters of the model. The original Schlumpf model has
three parameters, a quark mass, a paramter to determine the average momentum
of a quark and another parameter to determine the high momentum tail of the
nucleon wave function. These were chosen to reproduce the nucleon magnetic
moments, the proton charge radius, the proton GM at high momentum transfer,
and other observables. Including the effects of the pion cloud allows us to
choose different parameters than Schlumpf and still reproduce the same
quantities. There is also one more parameter needed to describe the
pion-nucleon form factor.
The figures shown represent a best fit, obtained
using reaonable values of the four parameters, to the
four nucleon electromagnetic form factors.
The different curves shown in the figures represent the results for
different parameter sets.
These figures are the basis for a 2002 paper
The resulting model wave functions reveal interesting
features regarding the shape of the nucleon. It can
be shaped like a peanut, sausage, bagel or pretzel. See
for more details.
- G.A. Miller, A.W. Thomas, and S. Théberge, Phys.Lett. B91, 192
S. Théberge, A. W. Thomas and
G. A. Miller Phys. Rev. D 22, 2838-2852 (1980)
A. W. Thomas, S. Théberge, and G. A. Miller Phys. Rev. D 24, 216-229
- S. Théberge, G. A. Miller, and A. W. Thomas Can.J. Phys. 60, 59 (1982)