Quark distributions in nuclear matter and the EMC effect

Abstract

Quark light cone momentum distributions in nuclear matter and the structure function of a bound nucleon are investigated in the framework of the Nambu-Jona-Lasinio model. This framework describes the nucleon as a relativistic quark-diquark state, and the nuclear matter equation of state by using the mean field approximation. The scalar and vector mean fields in the nuclear medium couple to the quarks in the nucleon and their effect on the spin independent nuclear structure function is investigated in detail. Special emphasis is placed on the important effect of the vector mean field and on a formulation which guarantees the validity of the number and momentum sum rules from the outset.

Role of the nuclear vector potential in deep inelastic scattering

“…It has been argued that the quark struck by the hard photon should not feel the nucleon vector potential 3V 0 , and accounting for this causes a shift in the argument of the distribution function, and a change in its normalization. This shift seems to have a significant effect on computed numerical results [8,16], but its presence is not immediately apparent in other work [17].…”

“…This can be expressed more formally using the techniques of Ref. [16] who observe that the quark Hamiltonian in the mean field approximation for nuclear matter at rest has the formĤ…”

“…The mean-field should provide important effects for quarks in the target ground state and should vanish for high-energy quarks. Thus both sets of authors [8,16] and [17] use a physically reasonable procedure. The rigorous task of deriving a vector potential with the ability to account for both the high and low energy limits of the quark self-energy in nuclear matter remains a task for the future.…”

Role of diquark correlations and the pion cloud in nucleon elastic form factors

“…The NJL model has a long history of success in the study of meson properties [20,22] and more recently as a tool to investigate baryons as 3-quark bound states using the relativistic Faddeev equation [26][27][28]. Recent examples include the study of nucleon parton distribution functions (PDFs) [29][30][31][32][33], quark fragmentation functions [34,35] and transverse momentum dependent PDFs [36,37]. Finally, we mention that the NJL model has been used to study the self-consistent modification of the structure of the nucleon in-medium and its role in the binding of atomic nuclei [38].…”

Spin-Dependent Structure Functions in Nuclear Matter and the Polarized EMC Effect

“…Our calculations are made within the framework developed by Bentz, Thomas, and collaborators [10,11], in which proper-time regularization [12 -14] is applied to the Nambu-Jona-Lasinio (NJL) model in order to simulate the effects of confinement. This model exhibits similar properties to the QMC model with the advantage that it is covariant.…”