Applications of a nonlinear evolution equation II: the EMC effect

TL;DR

This paper models the EMC effect through a nonlinear evolution equation, predicting nuclear modifications of parton distributions with minimal free parameters, highlighting the roles of shadowing, antishadowing, and nuclear deformation effects.

Contribution

It introduces a unified framework using the GLR-MQ-ZSR equation to predict nuclear and proton parton distributions with minimal parameters, emphasizing dynamical shadowing effects.

Findings

Nuclear shadowing emerges as a dynamical evolution result.

Antishadowing partially explains the enhancement of structure function ratios.

Gluon shadowing is weaker than quark shadowing in nuclei.

Abstract

The EMC effect is studied by using the GLR-MQ-ZSR equation with minimum number of free parameters, where the nuclear shadowing effect is a dynamical evolution result of the equation, and nucleon swelling and Fermi motion in the nuclear environment deform the input parton distributions. Parton distributions of both proton and nucleus are predicted in a unified framework. We show that the parton recombination as a higher twist correction plays an essential role in the evolution of parton distributions either of proton or nucleus. We find that the nuclear antishadowing contributes a part of enhancement of the ratio of the structure functions around $x\sim 0.1$, while the other part origins from the deformation of the nuclear valence quark distributions. We point out that the nuclear shadowing and antishadowing effects in the gluon distribution are not stronger than that in the quark distributions.