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Implications of the Nuclear EMC effect
The discovery more than thirty years ago, by the EMC Collaboration, that the deep-inelastic-scattering DIS structure functions are influenced by the nuclear environment stunned the nuclear physics community and brought quarks and gluons into the field with great impact. Moreover, Drell-Yan experiments (muon pair production in proton-nucleus scattering) do not observe an enhanced nuclear sea. A great length of time has passed, but despite a semi-infinite number of papers on the subject, there is no explanation for these experiments that is universally accepted. The use of conventional nuclear physics involving
nucleon and meson degrees of freedom fail to provide an explanation. Many models (related in one way or another to QCD) have been successful in reproducing data for deep inelastic scattering on nuclear targets, but fewer have described both the DIS and nuclear Drell-Yan experiments. Although there are some positive indications, no model has been used to predict correctly and unambiguously new independent phenomena. We review the history, emphasizing recently produced data, and discuss the best experimental prospects for future discovery.