The Shape of the Proton
Abstract
The aim of this talk is to interpret the recent exciting experimental results for proton and neutron electromagnetic form factors using Poincaré invariance and chiral symmetry. I discuss a relativistic interpretation for why the proton's ratio of charge to magnetic form factors, G_E/G_M, falls and why the ratio of Pauli to Dirac form factors QF_2/F_{1} is approximately constant. Poincaré invariance is respected by expressing the quark wave functions of the proton in terms of Dirac spinors. This is equivalent to using a lightcone representation in which quarks carry nonzero orbital angular momentum. Hence, the proton can be said to have a nonspherical shape. Reproducing the observed neutron G_E^n mandates the inclusion of the effects of a pion cloud. The full relativistic model with a pion cloud provides a good reproduction of all of the nucleon electromagnetic form factors, see G. A. Miller, Phys. Rev. C66, 032201 (2002).
 Publication:

APS April Meeting Abstracts
 Pub Date:
 April 2003
 Bibcode:
 2003APS..APR.B3003M