## Wayne State University Dissertations

#### Access Type

Open Access Dissertation

January 2014

Dissertation

Ph.D.

#### Department

Physics and Astronomy

Sergei Voloshin

#### Abstract

Since 2009, the Large Hadron Collider (LHC) at European Organization

for Nuclear Research (CERN) has been conducting experiments in $pp$,

Pb-Pb, as well as $p$-Pb collisions with the center of mass energy

ranging $\sqrt{{s}_{NN}}=0.9-5.05$~TeV. In this thesis, both,

estimates of background correlations in anisotropic flow, $v_1-v_5$,

measurements

in Pb-Pb collisions at

$\sqrt{{s}_{NN}}=2.76$~TeV, and azimuthally differential pion femtoscopy

of Pb-Pb collisions are reported.

Two particle azimuthal correlations are statistically the most precise

method of measuring anisotropic flow. The main drawback of this method

is its sensitivity to the non-flow correlations, which unlike real

flow, do not have geometrical origin. Non-flow contribution can be

estimated from two particle azimuthal correlations using $pp$ data.

Measurements of the non-flow contribution using the uQ method and

Scalar Product (SP) method are reported for $pp$ collisions at

$\sqrt{{s}_{NN}}=2.76$~TeV and $\sqrt{{s}_{NN}}=7$~TeV for the first

through fifth harmonics.

information on the geometry of the effective pion-emitting source. In

particular, its shape can be studied by measuring femtoscopic radii as

a function of the emission angle relative to the collision plane of

symmetry. The first measurements of azimuthally differential

femtoscopy in Pb-Pb collisions at $\sqrt{{s}_{NN}}=2.76$~TeV are

reported and compared to results from RHIC experiments at lower

energies. Oscillations of the extracted radii versus the emission

angle are measured, and

$R_{side}$ and $R_{out}$

oscillations are found to be out of phase. The relative amplitude of

the $R_{side}$ oscillations decreases in more central collisions,

however always remains positive. This indicates that the source is

out-of-plane extended, similar to that observed at RHIC energies.

Results are compared to existing hydrodynamical and transport model

calculations.

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