Evidence for enhancement of gluon and valence-quark distributions in nuclei from hard lepton-nucleus processes

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Abstract
Current data on deep-inelastic processes off nuclei are analyzed by using exact QCD sum rules for the total momentum and baryon charge of nuclei. Evidence for an overall enhancement of the gluon field in heavy nuclei (≥4%) is found which, combined with the calculation of nuclear shadowing, yields a substantial enhancement of valence-quark and gluon distributions at x≊0.1, as well as a suppression of the sea for x≤0.1. It is also shown that scaling violations lead to a strong decrease of shadowing for the sea at x≊0.05. Implications for disentangling the origin of internuclear forces are further discussed.