Short range structure of hadron and nuclear wave functions at high X

We discuss the short‐range structure of hadronic and nuclear wave functions expected in QCD. In addition to the ‘‘extrinsic’’ contributions associated with radiation from single partons, there is an ‘‘intrinsic’’ hardness of the high‐mass fluctuations of the wave function due to the spatial overlap of two or more partons.We argue that intrinsically‐hard partons, having large mass and/or large transverse momentum, will dominate in the region of large Feynman χF. Their rescattering in nuclear targets is expected to be larger than for extrinsically‐hard partons, leading to a suppressed production cross section for hadrons scattering on heavy nuclei. Experimental evidence for this exists for open charm, J/ψ, and Υ production at large χF.The effects of intrinsic hardness may be particularly striking in nuclear wave functions, where the overlap of partons belonging to different nucleons can give rise to cumulative (x≳1) phenomena. The data on backward cumulative particle production from nuclei supports the exis...