2-d Di-hadron Correlations at √sN N = 2.76 TeV using the ALICE experiment

Abstract

The Large Hadron Collider (LHC) at CERN Geneva, Switzerland, attempts to recre- ate the initial conditions at the begining of our universe. Heavy ions ( Pb208) are accelerated up to 0.999999 of the speed of the light and collided at √sN N = 2.76 T eV (center of mass energy per nucleon) in order to recreate the initial energy density (∼ 10−6s) after the Big Bang. The theory of Quantum Chromo Dynamics (QCD) predicts the formation of a primordial nuclear matter phase known as Quark Gluon Plasma (QGP) under these experimental conditions. This dissertation focuses on studying this QCD medium using data from the ‘A Large Ion Collider Experiment’ (ALICE). The study of two-dimensional two-particle correlations of emitted charged par- ticles carries valuable time integrated information of the dynamical QCD medium. Long-range correlations between particles in angular and momentum space generally can be attributed to collective behavior, which is not found in a superposition of elementary collisions. The focus of this thesis is to understand the long-range corre- lation structure observed in pseudo-rapidity (∆η) as a function of pT and to obtain better estimates of medium properties of the QGP, such as shear viscosity. The inter- pretation is based on empirical models describing well-established hydrodynamical collective flow phenomena and possible novel phenomena related to in-medium par- ton fragmentation. The flow and Gaussian parameters extracted from the fit model can be used to constrain medium properties such as the initial gluon density, the shear viscosity and the partonic energy transport coefficient.