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Pion Form Factor in the Light-Front
The pion electromagnetic form factor is calculated with a light-front quark
model. The "plus" and "minus" component of the electromagnetic current are used
to calculate the electromagnetic form factor in the Breit frame with two models
for the q\bar{q} vertex. The light front constituent quark models describes
very well hadronic wave function for pseudo-scalar and vector particles.
Symmetry problems arinsing in the light-front approach are solved by the pole
dislocation method. The results are compared with new experimental data and
with other quark models.Comment: 4 pages,1 figure (eps), Latex,AIP style.To appear in the proceedings
"IX Hadron Physics and VII Relativistic Aspects of Nuclear Physics: A Joint
Meeting on QCD and QGP, Hadron Physics-RANP,2004,Angra dos Reis, Rio de
Janeiro,Brazil.(some references are added and small mistakes are corrected.
Spin-1 Particle in the Light-Front Approach
The electromagnetic current of spin-1 composite particles does not transform
properly under rotations if only the valence contribution is considered in the
light-front model. In particular, the plus component of the current, evaluated
only for the valence component of the wave function, in the Drell-Yan frame
violates rotational symmetry, which does not allow a unique calculation of the
electromagnetic form-factors. The prescription suggested by Grach and
Kondratyuk [Sov. J. Nucl. Phys. 38, 198 (1984)] to extract the form factors
from the plus component of the current, eliminates contributions from pair
diagrams or zero modes, which if not evaluated properly cause the violation of
the rotational symmetry. We address this problem in an analytical and covariant
model of a spin-1 composite particle.Comment: To appear Brazilian Journal of Physics (2004), 4 pages, no figures.
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