The strong interactions between protons and neutrons (nucleons) in the dense interior of heavy nuclei are believed to be responsible for modifying the internal quark structure of the nucleon. This modification, known as the “EMC effect” [1,2], was observed to scale with nuclear density, yielding a modest A dependence in medium-to-heavy nuclei. Measurements of the EMC effect at Jefferson Lab [2,3] showed that this picture breaks down in light nuclei, with the EMC effect in 9Be, an anomalously low-density nucleus, being much larger than predicted.
As part of the commissioning run in Hall C after the 12 GeV upgrade data were taken on light nuclei including, for the first time, 10B and 11B . These new results confirm the initial conclusion that the EMC effect does not scale with nuclear density. A global analysis of all light nuclei is consistent with the hypothesis that the EMC effect scales with the overlap between neighboring nucleons. This is consistent with the observation of a correlation between the EMC effect and Short-Range Correlations (SRCs), which generate highly-relativistic nucleons in nuclei when these nucleons interact at very short distances. Measurements of SRCs in 10B and 11B were also made, and will allow us to extend the observation of the EMC-SRC correlation to additional light nuclei.
These data were taken as part of a much broader program, initiated by NSD scientist John Arrington, head of the Relativistic Nuclear Collisions Program, and completed earlier this year. The program included two experiments to map out both the EMC effect and the contribution of SRCs across all stable light nuclei . These experiments also included measurements on a variety of heavier nuclei, including 40Ca and 48Ca, to see how these effects change as a function of the neutron excess in nuclei, providing the first opportunity to try and separate density-dependent effects from potential isospin-dependent contributions.
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 JLab experiments E12-06-105 and E12-10-008