Visualization of Helium-4 and Beryllium Nuclei (IMAGE)
Caption
JLab experiment E03-103 made precise new measurements of the EMC effect in a variety of light nuclei. The results indicate that the effect does not depend on nuclear mass or density but rather on the microscopic structure of nuclei, usually neglected in high-energy measurements. This result hinges on the unusual structure of 9Be. Most of the time, it is in a configuration with two 4He-like clusters and an additional neutron orbiting around each other. The orbiting clusters yield a large radius and an anomalously low average density similar to that of the much less massive 3He. But the size of the EMC Effect in 9Be is much more similar to that of the denser nucleus of 12C. This is probably because most nucleons are contained within the high local densities of the clusters. The results suggest that the EMC effect may be entirely generated within these small, high-density clusters, where densities can briefly approach those in a neutron star.
Credit
Image: Peter Mueller (Argonne National Lab)
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