Nuclear Dependence of Structure Functions in Coordinate Space

Abstract

The momentum distributions of partons in bound nucleons are known to depend significantly on the size of the nucleus. The Fourier transform of the momentum ($\xbj$) distribution measures the overlap between Fock components of the nucleon wave function which differ by a displacement of one parton along the light cone. The magnitude of the overlap thus determines the average range of mobility of the parton in the nucleon. By comparing the Fourier transforms of structure functions for several nuclei we study the dependence of quark mobility on nuclear size. We find a surprisingly small nuclear dependence ($<2\%$ for He, C and Ca) for displacements $t=z \lsim 2.5$ fm, after which a nuclear suppression due to shadowing sets in. The nuclear effects observed in momentum space for \mbox{$\xbj \lsim 0.4$} can be understood as a reflection of only the large distance shadowing in coordinate space.