Session 1WC: The Physics of Nuclei Throughout Nuclear and High-Energy Physics

Nuclear Structure and Response

The nucleus is an intriguing quantum many-body system which simultaneously has strong two-nucleon correlations at short distances and rich shell structure and superfluid pairing at larger distances. Advances in computational nuclear physics allow us to address these issues simultaneously, yielding a high-resolution picture of nuclei. I will review recent progress in ab-initio computational nuclear emphasizing both these aspects and their experimental signatures.   

Detailed study of Short Range Correlations at Jefferson Lab

The force which holds the nucleus together has been under intense study for many decades. The nuclear shell model, which plays a central role in these investigations, has been very successful in reproducing low energy measurements, but is insufficient to predict medium energy results. The discrepancy is believed to originate from short range correlations, i.e. overlapping nucleons in the nucleus which briefly create densities close to those in neutron stars. Using an electron beam, these features of the nucleus can be isolated and studied at kinematics where $x_{bj} > 1$. In order to present the new results from Jefferson Lab, we will first highlight what has happened in the field over the last decade. We will also discuss the goals of the future related measurements scheduled to run at Jefferson Lab after the 12 GeV upgrade.   

The Neutron Structure Function

Knowledge of the neutron structure function is important for testing models of the nucleon, for a complete understanding of deep inelastic scattering (DIS) from nuclei, and for high energy experiments. As there exist no free neutron targets, neutron structure functions have been determined from deep inelastic scattering from the deuteron. Unfortunately, the short-range part of the deuteron wave function becomes important in extracting the neutron structure function at very high Bjorken $x$. New methods have been devised for Jefferson Lab experiments to mitigate this problem. The BONUS experiment involves tagging spectator neutrons in the deuteron, while the MARATHON experiment minimizes nuclear structure effects by a comparison of DIS from $^{3}$H and $^{3}$He. A summary of the status and future plans will be presented.   

The role of high-density clusters in the quark structure of nuclei

Given the extremely dense environment of a nucleus and the complex nature of QCD, there is no a priori reason to expect that this many-quark system should simply look like a collection of quasi-free nucleons. But to a very high degree, this is exactly what is observed in nature. Nonetheless, there are indications that at the quark level, there may be small changes to the internal structure of nucleons inside the dense nuclear environment. Recent measurements of the EMC effect suggest that the nuclear modification may related to short distance structures in nuclei, implying that two-body effects drive a significant part of the effect. I will present these results, their potential implications, and future plans aimed at testing this idea.   

The Role of Nuclear Physics in CC and NC Neutrino Reactions

An overview of the role played by nuclear physics in charge-changing and neutral current neutrino and anti-neutrino reactions with nuclei will be presented in this talk. The importance of using relativistic approaches when considering modern experiments will be illustrated and the differences between modeling inclusive and semi-inclusive reactions will be emphasized. Specifically, the relativistic Fermi gas model will be discussed and its limitations made clear; independent-particle approaches will be summarized, together with comments on where they may or may not be expected to apply; and for semi-inclusive reactions, the basics of the factorized spectral function approach will be presented.   

From QCD to Nuclear Physics

Lattice QCD offers the promise of quantitatively connecting low-energy nuclear physics with the fundamental theory of strong interactions. Significant progress in achieving this goal has been made in the last few years, with, for example, the first definitive calculations of light nuclei recently appearing. There remain significant challenges which must be overcome to connect these calculations to experimental results, including the ability to perform calculations with physical pion masses. I will review lattice QCD calculations of multi-hadron systems, providing a status report as well as future prospects.