Partonic rescatterings during jet fragmentation in the QCD vacuum

High energy collisions of small systems like Proton-Proton ($pp$) and Proton-Lead ($p$Pb) have demonstrated surprising evidence for the existence of collectivity where it had previously been thought not to occur. Specifically, the medium produced by these collisions at the Large Hadron Collider (LHC) exhibits signatures of a strongly interacting, thermalized quark-gluon plasma (QGP). Searches in many other small systems have so far been inconclusive. These strongly interacting partonic systems are described by Quantum Chromodynamics (QCD) which is generally separated into perturbative and nonperturbative energy regimes. Many of the interesting phenomena in QCD, including collectivity, are partially or entirely in the nonperturbative regime and present theoretical challenges. Experimental efforts therefore become an essential tool to understand and explore these surprising and unexpected phenomena. We postulate that collective effects similar to those observed in high energy collisions can emerge from the fragmentation and hadronization evolution of a partonic jet. We first describe an analysis procedure to search for these effects and define key observables. We demonstrate this procedure using Monte Carlo (MC) simulations which serve to establish a baseline for our observables~\cite{Parker1}. We subsequently apply our analysis procedure to the entire $pp$ collision data set produced at the LHC during Run II. We present a search for partonic collectivity inside jets using the Compact Muon Solenoid (CMS) detector at the LHC. We compare results from data to two MC simulations employing different phenomenological models. Deviations between data and both MC simulations are observed, in accordance with our initial postulate. We investigate and quantify these deviations through a series of measurements, validations, and cross-checks. The results yield new insights into QCD vacuum dynamics and parton fragmentation~\cite{Parker2}.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Natural Sciences

Grantor

Rice University

Year dc:date.issued

2024

Author dc:creator

• Gardner, Parker T

Advisor dc:contributor.advisor

• Li, Wei

• QCD
• jets
• CMS
• quark
• collectivity
• hydrodynamics
• parton
• LHC
• proton
• small system

Statement dc:rights

• Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1911/116090

OAI identifier oai:identifier

oai:repository.rice.edu:1911/116090