Hadrons in the nuclear medium

Abstract

Quantum chromodynamics (QCD), the microscopic theory of strong interactions, has not yet been applied to the calculation of nuclear wavefunctions. However, it certainly provokes a number of specific questions and suggests the existence of novel phenomena in nuclear physics which are not part of the traditional framework of the meson-nucleon description of nuclei. Many of these phenomena are related to high nuclear densities and the role of colour in nucleonic interactions. Quantum fluctuations in the spatial separation between nucleons may lead to local high-density configurations of cold nuclear matter in nuclei, up to four times larger than typical nuclear densities. We argue here that experiments utilizing the higher energies available upon completion of the Jefferson Laboratory energy upgrade will be able to probe the quarkgluon structure of such high-density configurations and therefore elucidate the fundamental nature of nuclear matter. We review three key experimental programmes: quasi-elastic electro-disintegration of light nuclei, deep inelastic scattering from nuclei at x > 1 and the measurement of tagged structure functions. These interrelated programmes are all aimed at the exploration of the quark structure of high-density nuclear configurations.The study of the QCD dynamics of elementary hard processes is another important research direction and nuclei provide a unique avenue to explore these dynamics. In particular, we argue that the use of nuclear targets and large values of momentum transfer at energies available with the Jefferson Laboratory upgrade would allow us to determine whether the physics of the

Electron scattering from high-momentum neutrons in deuterium

“…Using the lightcone prescription [Eq. (8)] for the momentum distribution of the initial proton (solid curve), good agreement between the data and our Monte Carlo simulation is observed up to cos θ pq ≈ −0.3. The result for the nonrelativistic wave function [Eq.…”

“…A large number of models have been proposed to explain the EMC effect. A good review of this subject is given by Sargsian et al [8].…”

“…(3) and (4)] or as the "internal momentum" in the light-cone description, Eqs. (5)- (8). From the spectator nucleon kinematics, we then calculate the initial four-momentum of the struck nucleon, determine the scattered electron kinematics in the rest frame of that nucleon, and then transform it back to the laboratory frame.…”

Dependence of the wave function of a bound nucleon on its momentum and the EMC effect

“…Hence such a region is suitable for the extraction of the properties of the free neutron from scattering processes off the deuteron and 3 He using the analog of the Chew-Low procedure (see e.g. the discussion in [9]). For the same reason, the 3% upper limit for the change of the magnetic nucleon radius obtained from the analysis of the Q 2 dependence of the inclusive (e, e ′ ) cross section near the quasi-elastic peak [34], implies a much weaker limit on the average change of the nucleon radius in nuclei.…”

“…Experiments at Jlab, especially after the 12 GeV upgrade, will be able to break the deadlock by performing a series of dedicated experiments (see e.g. [9]). …”