About this Research Topic
Historically, early electron scattering experiments that knocked protons out of nuclei were unable to describe the observed cross sections beyond simple independent particle shell models. Theory predictions had to account for overlapping nucleon-nucleon distributions, or short-range nucleon-nucleon correlations, in order to account for the loss of shell spectral strength. Subsequent experiments have been able to confirm the observation of nucleons in short-range correlations as well as to measure details of their isospin preference. While nucleons by themselves are well-described in terms of their constituent quarks and gluons, the observation and characteristics associated with nucleons in short-range correlations arises from interactions of the quark systems of these nucleons. Describing nucleons in terms of their quarks and gluons as well as their characteristic interactions amongst other nucleons in bound nuclei is a key goal in nuclear physics.
Color transparency (CT), a unique prediction of Quantum Chromo Dynamics, is a phenomenon that can provide insight in connecting characteristics of nuclei and their description in terms of quark-gluons degrees of freedom. CT refers to the vanishing of final (and/or initial) state interactions of hadrons with the nuclear medium for exclusive processes at high momentum transfers. Color transparency has been observed at high energies but its onset at intermediate energies is key to a complete understanding of the phenomenon and other related processes such as hadronization in the medium. The onset of CT has been observed in exclusive production of mesons but not in baryons. This is lack of unambiguous observation of CT in baryons is puzzling and drives future theoretical and experimental efforts in this field.
Within this collection we wish to explore the options for new theoretical and experimental efforts towards studying the partonic origin of nuclear structure, the insights we can gain from nucleon-nucleon short range correlations and resolving the puzzling lack of color transparency in protons as reported by a new A(e,e’p) experiment at the recently upgraded Jefferson Lab. This Research Topic aims to serve as a roadmap for the future developments and a guide to areas for possible collaboration.
The objectives of this research topic are to develop theory and experimental approaches that will successfully describe partonic origins of matter including the apparent reaction dependence of this fundamental prediction of QCD, the differences between three-quark and quark-antiquark states and the subsequent nucleon modifications and interactions including correlations at short-range. Some ideas that will be explored are: connections to form factors, virtuality dependence of FSI and connections to SRC, halographic light-front QCD, connections to quantum entanglement, connections to hadronization. New experimental ideas that will be discussed include: re-scattering in D(e,e’p), diffractive break-up of the deueteron, polarized deuteron and 3He reactions, extreme kinematics, use of spectator tagging and new possibilities at JLab, J-PARC, PANDA and the future EIC.
Keywords: Color coherence, Color transparency, Hadronization, Color screening, Final State Interactions, Short-range correlations, EMC Effect, Electron Ion Collider
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