CORRELATION AND BALANCE FUNCTIONS OF IDENTIFIED HADRON
PAIRS IN AU+AU COLLISIONS AT RHIC

Ph.D. Dissertation Public Defense
presented by Launa Di Carlo

Abstract:
Heavy-ion collisions are used to study the properties of the Quark
Gluon Plasma (QGP), a hot and dense strongly-interacting system of
deconfined quarks and gluons. Such systems can be formed in collisions
of 197-Au nuclei at the RHIC facility. Correlation and balance
functions will be used to study these collisions. The correlation
functions provide information on reaction mechanisms and the balance
functions indicate the conditional probability that a pair of particle
species was locally produced together during the collision. The
correlation and balance functions of the full 3×3 matrix of (π, K,
p)⊗(π, K, p) species pairs versus the relative rapidity, ∆y = y1 − y2,
and relative azimuthal angle, ∆φ = φ1 − φ2, will be reported for 200
GeV Au+Au collisions versus the event centrality collected by the STAR
experiment. Special care was taken to ensure that there were no direct
correlations between the centrality definition and the correlations
analysis. The correlation functions, R2, are fully-corrected for
several detector effects. The balance functions, B2, are constructed
from linear combinations of these fully-corrected R2 correlation
functions and efficiency-corrected single particle cross-sections.
Detector efficiency corrections are shown via a “closure” test to be
accurate. The effects of pair cuts on either the relative momentum or
the invariant mass in order to remove femtoscopy and weak decays,
respectively, will be explored. The collision centrality dependence of
the balance function projections is weak. The balance function
integrals are also weakly dependent on the collision centrality. The
experimental data is compared to several model event generators, which
indicates that the hadronic cascade models (UrQMD and SMASH) more
accurately reproduce the B2 integrals than does the AMPT and HIJING
models.