New Measurements of the EMC Effect in Light Nuclei and at Large x

The modification of structure functions in nuclei (the EMC effect) has been the focus of intense experimental and theoretical study since the original observation in 1983. The EMC effect unequivocally demonstrates that quark distributions in nuclei are not simply the incoherent sum of the nucleon quark distributions. However, progress in understanding the root cause of these modifications has been hampered by the complexity of nuclear structure, making it difficult to disentangle the “conventional” nuclear effects of Fermi motion and binding from true medium modifications to nucleon structure. Experiment E03—103 at Jefferson Lab made measurements of nuclear structure function ratios from few—body nuclei (3He and 4He) to deuterium, where the nuclear structure is well known, and for a range of nuclei, A = 3 to 197, at large x, where effects from Fermi motion and binding dominate.