Nucleon Structure Functions from a Chiral Soliton in the Infinite

We study the frame dependence of nucleon structure functions obtained within a chiral soliton model for the nucleon. Employing light cone coordinates and introducing collective coordinates together with their conjugate momenta, translational invariance of the solitonic quark fields (which describe the nucleon as a localized object) is restored. This formulation allows us to perform a Lorentz boost to the infinite momentum frame of the nucleon. The major result is that the Lorentz contraction associated with this boost causes the leading twist contribution to the structure functions to properly vanish when the Bjorken variable x exceeds unity. Furthermore we demonstrate that for structure functions calculated in the valence quark approximation to the Nambu–Jona–Lasinio chiral soliton model the Lorentz contraction also has significant effects on the structure functions for moderate values of the Bjorken variable x. ∗ Supported in part by the Deutsche Forschungsgemeinschaft (DFG) under contract Re 856/2-3, the Graduiertenkolleg Hadronen und Kerne at Tübingen University, and the U.S. Department of Energy (D.O.E.) under contract DE–FE–02–95ER40923.