Detailed study of the nuclear dependence of the EMC effect and short-range correlations

TLDR

Nuclear density has been key to explaining the EMC effect and the presence of high‑momentum nucleons from short‑range correlations. The study aims to constrain models of the EMC effect and short‑range correlations by carefully examining experimental data. The authors perform a detailed analysis of the EMC effect and SRCs, comparing data to predictions and scaling models, and quantitatively relate the two observables. New light‑nucleus data reveal that neither the EMC effect nor SRCs follow simple density‑dependent models, implying that the EMC effect is driven by high‑density configurations or large virtuality of high‑momentum nucleons, suggesting a local‑environment dependence and a link between the two phenomena, though no model is yet preferred.

Abstract

Background: The density of the nucleus has been important in explaining the nuclear dependence of the quark distributions, also known as the EMC effect, as well as the presence of highmomentum nucleons arising from short-range correlations (SRCs). Recent measurements of both of these effects on light nuclei have shown a clear deviation from simple density-dependent models. Purpose: A better understanding of the nuclear quark distributions and short-range correlations requires a careful examination of the experimental data on these effects to constrain models that attempt to describe these phenomena. Methods: We present a detailed analysis of the nuclear dependence of the EMC effect and the contribution of SRCs in nuclei, comparing to predictions and simple scaling models based on different pictures of the underlying physics. We also make a direct, quantitative comparison of the two effects to further examine the connection between these two observables related to nuclear structure. Results: We find that, with the inclusion of the new data on light nuclei, neither of these observables can be well explained by common assumptions for the nuclear dependence. The anomalous behavior of both effects in light nuclei is consistent with the idea the the EMC effect is driven by either the presence of high-density configurations in nuclei or the large virtuality of the highmomentum nucleons associated with these configurations. Conclusions: The unexpected nuclear dependence in the measurements of the EMC effect and SRC contributions appear to suggest that the local environment of the struck nucleon is the most relevant quantity for explaining these results. The common behavior suggests a connection between the two seemingly disparate phenomena, but the data do not yet allow for a clear preference between models which aim to explain this connection.