Recent experimental results on the EMC effect are presented. The ratios of structure functions for nuclei and deuterium measured by the two muon experiments at CERN show a clear enhancement of a few percent for x < 0.25. At x below 0.05 substantial shadowing with little Q 2 dependence has been observed by a dedicated low angle experiment of the EMC. No significant nuclear mass dependence of R = σ L σ T has been seen in the SLAC experiment E140. There are several indications that the Q 2 evolution of nuclear structure functions deviates from the expectations of perturbative QCD and that the gluon distribution in nuclei is harder than in free nucleons. This is possibly caused by nucleon-nucleon correlations on the quark-gluon level. Many aspects of the EMC effect are presently being investigated by the high energy muon experiment of the NMC collaboration at CERN and a Drell-Yan experiment at FNAL. First results can be expected soon. They will help to develop a better understanding of nuclear effects in quark and gluon distributions.
KeywordsStructure Function Gluon Distribution Quark Distribution Nuclear Effect High Twist
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