Systematic Azimuth Quadrupole and Minijet Trends from Two-Particle Correlations in Heavy-Ion Collisions |
Posted on:2014-10-12 | Degree:Ph.D | Type:Dissertation |
University:University of Washington | Candidate:Kettler, David | Full Text:PDF |
GTID:1450390005497406 | Subject:High Energy Physics |
Abstract/Summary: | |
eavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) produce a tremendous amount of data but new techniques are necessary for a comprehensive understanding of the physics behind these collisions. We present measurements from the STAR detector of both pt-integral and pt-differential azimuth two-particle correlations on azimuth (phi) and pseudorapidity (eta) for unidentified hadrons in Au-Au collisions at a center of mass energy = 62 and 200 GeV. The azimuth correlations can be fit to extract a quadrupole component---related to conventional v2 measures---and a same-side peak. The azimuth quadrupole component is distinguished from eta-localized same-side correlations by taking advantage of the full 2D eta and phi dependence. Both pt-integral and pt-differential results are presented as functions of Au-Au centrality. We observe simple universal energy and centrality trends for the pt-integral quadrupole component. pt-differential results can be transformed to reveal quadrupole pt spectra that are nearly independent of centrality. A parametrization of the pt-differential quadrupole shows a simple pt dependence that can be factorized from the centrality and collision energy dependence above 0.75~GeV/c.;Angular correlations contain jet-like structure with most-probable hadron momentum ~ 1 GeV/c. For better comparison to RHIC data we analyze the energy scale dependence of fragmentation functions from e+-e - collisions on rapidity y. We find that replotting fragmentation functions on a normalized rapidity variable results in a compact form precisely represented by the beta distribution, its two parameters varying slowly and simply with parton energy scale Q. The resulting parameterization enables extrapolation of fragmentation functions to low... |
Keywords/Search Tags: | Collisions, Quadrupole, Azimuth, Correlations, Fragmentation functions, Energy |
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