Neutral Pion-hadron Correlations in 200 GeV Au + Au Collisions

Abstract

In a newly explored kinematic condition which is extremely hot and dense, the asymptotic freedom feature of Quantum Chromodynamics (QCD) predicts a deconfined phase of nuclear matter, known as quark-gluon plasma (QGP), where quarks and gluons can move freely like a perfect liquid. The QGP can be produced using the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory. During these collisions, high momentum partons are produced. These partons fragment into jets which are collimated sprays of particles. In the case that the QGP is formed, these hard partons lose energy when traversing the QGP. Therefore, the resulting jets are modified, which is observed as a angular broadening and modification of momentum distribution of jet particles. Hence, the study of jet modifications helps to understand the properties of the QGP. In this research, jets are studied using pi0-hadron azimuth correlations which use high momentum neutral pions as triggers to indicate the present of a jet. The azimuth correlations, known as jet functions, between the trigger pi0 and the charged hadrons are corrected for detector efficiency and underlying flow harmonics up to the fourth order. The jet functions are used to extract angular width and per trigger yields of the jets. This research found the angular broadening and enhancement of soft jet particles in Au+Au collisions at 200 GeV compared to p+p results, while hard jet particles are suppressed but no significant angular broadening is observed. To be able to fully interpret the modification observed in heavy-ion collisions, a deeper understanding of the initial state of confined quarks in the nuclei is needed. Therefore, the next era of nuclear physics requires an Electron-Ion Collider (EIC) to construct the comprehensive nucleon tomography in different phase spaces. This dissertation details work performed to develop a compact aerogel ring-imaging Cherenkov detector called the mRICH with a focusing Fresnel lens to overcome the space limitation in the EIC detector.

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