### Speaker

### Description

The Covariant Spectator Quark Model, successful

in the description of the nucleon elastic

form factors revealed by the Jefferson Lab

polarization transfer experiments,

has been extended to the calculation

of transition form factors associated

to several light nucleon resonances $N^\ast$.

The electromagnetic structure of the $N^\ast$

are characterized by the

$\gamma^\ast N \to N^\ast$ transition form factors.

Combining the electromagnetic structure of the

constituent quarks, calibrated by the nucleon data,

with appropriated ansatz for the radial wave functions

of the resonances, we are able to estimate the

transition for factors for the resonances

$N(1440)\frac{1}{2}^+$,

$N(1535)\frac{1}{2}^-$ and

$N(1520)\frac{3}{2}^-$, based on

the parametrization of the nucleon radial wave function

(nucleon shape) with no adjustable parameters.

The calculations take into account exclusively

the effect of the valence quarks

and are in good agreement with the data

for momentum transfer $Q^2 > 2$ GeV$^2$,

with a few exceptions.

The exceptions are discussed in terms of the

role of the valence quarks and the meson cloud.

All the estimates are based on

the parametrization of the nucleon structure,

and can be tested in a near future

for large transfer momentum at the

Jefferson Lab (12 GeV upgrade).

The model can also be extended to the $\Delta(1232)\frac{3}{2}^+$,

with the assistance of the results from lattice QCD, to estimate

the radial wave function of the $\Delta(1232)$ valence quark core.

The model estimates are in agreement with the

empirical data when theoretical and phenomenological

parametrizations of the pion cloud are taken into account.

### Summary

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