Access Type

Open Access Dissertation

Date of Award

January 2024

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Physics and Astronomy

First Advisor

Joern Putschke

Abstract

Small collision systems, such as that between a proton or deuteron and a heavy-ion, were originally studied to assess cold nuclear matter (CNM) effects but have produced surprising results at RHIC and the LHC over the last several years. Namely, observations of jet yield suppression (enhancement) in central (peripheral) p/d+A events have motivated further investigations into small systems, including the search for signs of Quark-Gluon Plasma (QGP) formation. This thesis focuses primarily on an analysis of correlations of hard and soft particle production in √s_NN = 200 GeV p+Au collisions in STAR. Jets and Underlying Event (UE) are measured at mid-rapidity (perpendicular to each other) and correlated with Event Activity (EA) at large backward-rapidity. The UE is measured differentially with respect to pseudorapidity and the leading jet. This analysis takes an experimental approach to understanding the observed jet yield modification in small systems and whether it results from the production of a medium. The data disfavor QGP production and instead suggest that the observed jet yield modification is due to an anti-correlation between the leading jet and the soft particle production used to estimate centrality. This could result in jet events being mis-classified as more peripheral on average, manifesting as a suppression of jet yield in central relative to peripheral events. Further kinematic correlations are measured in an attempt to elucidate the underlying physics that are not yet properly described by small system models. Future data from sPHENIX could provide further jet measurements to understand the correlations between hard and soft particle production in small systems.

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