Abstract
The past decade has provided a much clearer picture of the structure of high-momentum components in nucleons, associated with hard, short-distance interactions between pairs of nucleons. Recent Jefferson Lab data on light nuclei suggest a connection between these so-called 'short-range correlations' and the modification of the quark structure of nucleons in the nuclear environment. In light of this discovery that the detailed nuclear structure is important in describing the nuclear quark distributions, we examine the potential impact of the isospin-dependent structure of nuclei to see at what level this might yield flavor-dependent effects in nuclear quark distributions.
Highlights
A small but important part of the Jefferson Lab (JLab) program involves studies of the highmomentum structure of nuclei, which requires high-energy interactions to probe cleanly [1]
The overlap probability is one method of examining the impact of local density, using the probability of two nucleons having significant overlap as an overall measure of the possible contribution to pdf modification due to the possible contribution from direct quark exchange between the nucleons or more exotic 6-quark or hidden color configurations. This set of quantities can be calculated from ab initio calculations of nuclear structure for light nuclei, providing predictions for the EMC effect in light nuclei, which will be measured in an approved experiment at Jefferson Lab [44]
Density-dependent scaling is significantly different from the others, and is ruled out by the existing data on 3He, 4He, 9Be, and 12C [14]. This is not surprising, as the simple density dependence picture was already excluded based on these data, but this demonstrates that accounting for the difference between proton and neutron distributions does not yield a significant improvement in the prediction
Summary
A small but important part of the Jefferson Lab (JLab) program involves studies of the highmomentum structure of nuclei, which requires high-energy interactions to probe cleanly [1]. Questions about potential final-state interactions have been raised [35], but other polarization observables have some sensitivity to these effects [36] and future measurements will be able to map out the behavior in more detail [37] For both the binding and off-shell contributions, the large momenta and energies, associated mainly with nucleons in short-range correlations, are the direct cause of the EMC effect, yielding the observed correlation between the EMC effect and presence of SRCs. If the EMC effect is driven by the ‘local density’ observed by the struck nucleon, e.g. is due to direct quark exchange between nucleons with substantial overlap, all short-distance configurations - nn, np, and pp pairs - will contribute. While this idea has been discussed [1, 38], exisint data on the EMC effect are been insufficient to claim an flavor-dependent effect
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