Session J03: Advances in Nucleon Structure and Medium Modifcations Studies

Nucleon Structure: Overview and Recent Results

The study of nucleon structure is one of the most intriguing quests in nuclear physics. How the fundamental properties of the nucleon such as mass and spin emerge from its constituents is central in our understanding of QCD. Significant experimental efforts and theoretical advancements have been made over decades revealing that the nucleons are a complex and dynamic system of quark and gluons. To fully describe the 3D structure of the nucleon, much attention has been focused towards the multi-dimensional imaging in momentum and position space from the one-dimensional distribution functions in recent years. In this talk, I will review the current understanding of the nucleon structure and highlight selected results from recent studies with particular focus to the programs at JLab and RHIC.   

Probing Flavor Dependence of the EMC Effect

The correlation between the short-range correlations (SRCs) and the EMC effect suggests that there is potentially a closer connection between these two effects. This raises the possibility of an isospin dependent EMC effect in non-isoscalar nuclei due to the np dominance of the SRCs. However, there has been no conclusive experimental evidence for the isospin dependence or lack thereof for the EMC effect. Recent analyses have investigated the EMC-SRC correlation under two separate assumptions: the dominance of the extit{np} pairs contributing to the EMC effect (high virtuality) and the isospin-independent EMC effect (local density), and observed no isospin dependence of the EMC effect. We will present the new results on a global analysis that has been performed using the same approaches followed in these analyses with all the existing experimental data.   

Exploring Hadronization Mechanisms with SIDIS Production off Nuclei

Over the last few decades, several hard interactions studies have been dedicated to understand the basic mechanisms of color propagation and hadron production in nuclei. The process referred to as hadronization or fragmentation, in which the energetic struck quark transforms to color-neutral hadrons, is an effective way to probe the confinement dynamics of Quantum Chromo-Dynamics, the theory of strong interactions, and shed light on the non-perturbative formation of observed hadrons. This talk will discuss the first-ever analysis of the semi-inclusive deep inelastic scattering (SIDIS) of $Lambda$ hyperons in the current and target fragmentation regions using various nuclear-target data-sets collected with the Jefferson lab 6 GeV beam energy and the CLAS detector. Results on hadronic multiplicity ratios and transverse momentum broadening will be presented along with a qualitative discussion of other CLAS6 meson studies. The measured observables are sensitive to both fragmentation stages and could potentially constrain the existing theoretical models with different predictions about the hadronization time-scales. The extracted results of the CLAS6 SIDIS production channels in addition to the upcoming color propagation studies with the Jefferson lab CLAS12 detector would potentially improve our understanding of nucleon structure as well as the space-time evolution of hadrons at intermediate energies.