Chiral solitons in nuclei: saturation, EMC effect, and Drell-Yan experiments

Relativistic and Nuclear Medium Effects on the Coulomb Sum Rule

In light of the forthcoming high precision quasielastic electron scattering data from Jefferson Lab, it is timely for the various approaches to nuclear structure to make robust predictions for the associated response functions. With this in mind, we focus here on the longitudinal response function and the corresponding Coulomb sum rule for isospin-symmetric nuclear matter at various baryon densities. Using a quantum field-theoretic quark-level approach which preserves the symmetries of quantum chromodynamics, as well as exhibiting dynamical chiral symmetry breaking and quark confinement, we find a dramatic quenching of the Coulomb sum rule for momentum transfers |q|≳0.5  GeV. The main driver of this effect lies in changes to the proton Dirac form factor induced by the nuclear medium. Such a dramatic quenching of the Coulomb sum rule was not seen in a recent quantum Monte Carlo calculation for carbon, suggesting that the Jefferson Lab data may well shed new light on the explicit role of QCD in nuclei.

How well do we know the neutron structure function?

We present a detailed analysis of the uncertainty in the neutron F(2n) structure function extracted from inclusive deuteron and proton deep-inelastic scattering data. The analysis includes experimental uncertainties as well as uncertainties associated with the deuteron wave function, nuclear smearing, and nucleon off-shell corrections. Correctly accounting for the Q(2) dependence of the data and calculations and restricting the nuclear corrections to microscopic models of the deuteron, we find a significantly smaller uncertainty in the extracted F(2n)/F(2p) ratio than in previous analyses. In addition to yielding an improved extraction of the neutron structure function, this analysis also provides an important baseline that can be compared to future, model-independent extractions of neutron structure to examine nuclear medium effects in the deuteron.

Neutron properties in the medium

We demonstrate that for small values of momentum transfer Q2 the in-medium change of the GE/GM form factor ratio for a bound neutron is dominated by the change in the electric charge radius and predict within stated assumptions that the in-medium ratio will increase relative to the free result. This effect will act to increase the predicted cross section for the neutron recoil polarization transfer process 4He(e-vector,e'n-vector)3He. This is in contrast with medium modification effects on the proton GE/GM form factor ratio, which act to decrease the predicted cross section for the 4He(e-vector,e'p-vector)3H reaction. Experiments to measure the in-medium neutron form factors are currently feasible in the range 0.1<Q2<1 GeV2.