We explore the theoretical observation that within the leading twist approximation, the nuclear effects of shadowing and antishadowing in nonperturbative nuclear parton distribution functions (nPDFs) at the input QCD evolution scale involve diffraction on nucleons of a nuclear target and originate from merging of two parton ladders belonging to two different nucleons, which are close in the rapidity space. It allows us to propose that for a given momentum fraction xIP carried by the diffractive exchange, nuclear shadowing and antishadowing should compensate each other in the momentum sum rule for nPDFs locally on the interval ln(x/xIP)≤1. We realize this by constructing an explicit model of nuclear gluon antishadowing, which has a wide support in x,10-4<x<0.2, peaks at x=0.05-0.1 at the level of ≈15% for Pb208 at Q02=4GeV2 and rather insignificantly depends on details of the model. We also studied the impact parameter b dependence of antishadowing and found it to be slow.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics