The Valence Quark Structure of the Nucleon

Authors

Christopher A. Leon, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Physics

First Advisor's Name

Misak Sargsian

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Rajamani Narayanan

Second Advisor's Committee Title

committee member

Third Advisor's Name

Werner Boeglin

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Mirroslav Yotov

Fourth Advisor's Committee Title

committee member

Keywords

QCD, valence quarks, nuclear theoretical physics

Date of Defense

5-27-2022

Abstract

The nucleon is a composite object, formed from a sea of quarks, anti-quarks and gluons being continuously created and annihilated. Among this complexity, however, there are three valence quarks that give the nucleon its baryon and flavor numbers. Here we investigate the dynamical structure of valence quarks inside the nucleon. The primary tool used will be patron distribution functions (PDFs), which give the distribution of momentum fraction, x, of the quarks and gluons inside the nucleon. By examining the PDFs of the valence quarks from phenomenological fits, we derive a new model-independent relation of PDF peaks and connect it to quantum chromodynamics (QCD) evolution. This new relation can be used as a constraint in future extractions of PDFs. Next, we outline a model we created, the residual field model, to give a mean-field description of the valence quarks inside the nucleon, which will act as a baseline to study short-range quark–quark interactions. The model treats valence quarks as effective fermions of fixed number inside a valence subsystem, while the rest of the nucleon (gluons, sea quarks/anti-quarks, a pion cloud, etc.) exists in a residual subsystem. The valence PDFs are then calculated within the effective light-front diagrammatic approach with the introduction of non-perturbative light-front valence-quark and residual wave functions. Good quantitative agreement is found with existing phenomenologically derived down valence PDFs. While qualitatively we replicate the up-valence distribution, a systematic underestimation at large x leads us to conclude that the addition of hard gluon exchanges is needed to accurately describe the large x region. We then outline how to use perturbative QCD to describe those hard interactions and incorporate them into the model.

Identifier

FIDC010812

ORCID

https://orcid.org/0000-0002-9541-3013

Previously Published In

Leon, C., & Sargsian, M. (2022). Residual mean field model of valence quarks in the nucleon. The European Physical Journal C, 82(4), 1-21.

Leon, C., & Sargsian, M. (2019). A non-perturbative model of mean field valence quarks. Light Cone 2019-QCD on the Light Cone: From Hadrons to Heavy Ions, 56.

Leon, C., Sargsian, M. M., & Vera, F. (2021). A Novel Feature of Valence Quark Distributions in Hadrons. Physics, 3(4), 913-923.

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Recommended Citation

Leon, Christopher A., "The Valence Quark Structure of the Nucleon" (2022). FIU Electronic Theses and Dissertations. 5127.
https://digitalcommons.fiu.edu/etd/5127