# Correlation and balance functions of identified hadron pairs in Au+Au collisions at RHIC.

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**Event category:**Lecture

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.