Nucleon form factors and spin content in a quark-diquark model with a   pion cloud
  We propose a new model of the nucleon in which quark-diquark configurations immersed in a pion cloud are treated in a manner consistent with Poincar\'e invariance. With suitably chosen parameters, the computations employing this model reproduce the measured electromagnetic form factors and the quark-spin contribution to the total nucleon angular momentum. 
Ian C. Cloet and Gerald A. Miller
nucl-th nucl-ex