الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In particle collisions such as proton-proton collisions, a number of very interesting phenomena
have been observed, which are still not entirely understood. The observation
of the heavy ion like ridge that observed in pp collisions suggests the need for a study
of the correlations and thus also Bose-Einstein effects in high multiplicity pp collisions.
Interesting phenomena have been observed in pp collisions already in 2011: an unexplained
ridge structure was observed in two-particle correlations in angular difference,
which created excitement in the field but was left until now unexplained.
Intensity interferometry in particle physics is a direct and powerful experimental
method to determine the shapes, sizes and lifetimes of the emitting sources of particles.
In particular, boson interferometry which plays an important rule in investigating the
space-time structure of particle production processes. Bose-Einstein correlations (BEC)
between two identical bosons reflect both geometrical and dynamical properties of the
particle emitting source.
In this thesis we study Bose Einstein Correlations, i.e. measurements of the distance
distribution of particles in the 4-vector momentum space. It will be of great interest to
make such measurements in pp collisions and study the evolution of the ’source sizes’ of
the interference regions as function of produced pair kinematics. The CMS experiment
is especially well tailored for these kinds of measurements, since it has an excellent
central tracker allowing make very precise measurements of the charged particles that
leave the interaction region of the collision. We therefore make these measurements
based on charged particles, i.e. basically study the charged pion correlations. This is the
main topic of the thesis.
In this thesis we study Bose-Einstein correlations in proton-proton at the highest
energies available in the laboratory. The experimental data is collected with the Compact
Muon Solenoid (CMS) detector located at the Large Hadron Collider (LHC) at
the European Organization for Nuclear Research (CERN) near Geneva, Switzerland.
We investigated BEC for proton-proton colliding beams at 7 TeV centre-of-mass energy
recorded at CMS in 2010, in addition to the 13 TeV centre-of-mass energy proton-proton
collisions recorded in 2015. The minimum bias (MB) and high multiplicity (HM) events
from both energies were used in our study.
The first chapter of the current thesis introduces the historical and theoretical background
of Bose-Einstein Correlations. It also explains the derivation of BEC correlation
function and its parametrization. A brief introduction to the LHC collider and the structure
of the CMS experiment and its sub-systems is introduced in the second chapter.
The third chapter states the different data sets and MC simulations used in the present
analysis, and explains the methods of event and track selections used in our analysis. It
also contains the analysis of Bose Einstein Correlations and results of fitting the Bose-
Einstein correlation function. The correlation function parameters are also studied as
functions of both charged-particle multiplicity and mean-transverse momentum of the
correlated pairs.