Access Type

Open Access Dissertation

Date of Award

January 2019

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Physics and Astronomy

First Advisor

Joern . Putschke

Abstract

Ultra-relativistic heavy ion collisions produced at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) produce a new state of matter of deconfined quarks and gluons (partons) called the quark-gluon plasma (QGP). This plasma of deconfined but strongly coupled partons is believed to have been the primary state of matter in the universe up to a few milliseconds after the Big Bang. High energy partons produced in hard scatterings early in the collision can be used to probe the entire lifetime of the QGP. These partons propagate through and interact with the QGP before fragmenting into collimated sprays of hadrons called jets. Modification of these jets due to interaction with the QGP, also known as jet quenching, can provide insight into the interactions between the colored probe and the strongly interacting medium.

Two analyses utilizing specific ``hard-core'' di-jet events identified at the STAR detector at RHIC are presented, using Au+Au and p+p collisions at sqrt(s_NN) = 200 GeV.

In the di-jet hadron correlations, charged hadron yield with respect to the reconstructed jet axes allow for measurement of the redistribution of energy within the constituents of a jet due to interactions with the medium. It is shown that these ``hard-core'' di-jets are significantly less modified by the medium than what is seen in the inclusive jet population, with relatively vacuum-like widths and constituent yields.

In the differential di-jet imbalance measurement, the di-jet definition used to identify hard-core di-jets is systematically varied in two parameters: the jet resolution parameter, R, and the hard constituent transverse momentum threshold, p_T^{const}, which controls the selection of jets with harder or softer fragmentation patterns. It is found that the amount of modification experienced by the di-jet population is sensitive to the selection of these two parameters. The ability to control the amount of modification in a jet sample in a systematic manner suggests the possibility of Jet Geometry Engineering, the ability to control the path length of a jet in the QGP, which would allow for more direct study of the path length dependence of partonic energy loss.

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