Studies of Jet Modification in Heavy Ion Collisions with the CMS Experiment

In the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC), lead ions are collided at ultra-relativistic velocities to produce Quark-Gluon Plasma (QGP), a state of matter where quarks and gluons are deconfined and move collectively. Jets are produced in high-momentum transfer parton scatterings prior to and independently of QGP formation, and serve as natural probes of its properties. As the high-energy partons pass through the QGP, they lose energy through medium-induced gluon radiation and elastic scattering, resulting in jets that are modified with respect to the vacuum baseline. In this thesis, jet modification is quantified by measuring the jet production cross section as a function of jet radius in inclusive jets and the jet axis decorrelation in jets recoiling from isolated photons in Lead-Lead (PbPb) and Proton-Proton (pp) collisions. Both measurements indicate that effects of medium-induced jet broadening may be balanced by survivor bias in PbPb collisions, potentially due to differences in the magnitude of quenching of wide versus narrow jets. The results underline the importance of constraining the initial jet kinematics with bosons, which are unmodified by the QGP.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Physics

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2025

Author dc:creator

• Park, Mary Isabelle

Advisor dc:contributor.advisor

• Lee, Yen-Jie

Statement dc:rights

• Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
• Copyright retained by author(s)

Licence dc:rights.uri

• https://creativecommons.org/licenses/by-nc-nd/4.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/164159

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/164159