Particle Production in pp and Heavy Ion Collisions from $\sqrt{s_{NN}}$ = 200 GeV to 5.5 TeV

Exploring the creation of Quark Gluon Plasma (QGP), a new state of Nuclear matter is the main aim in Relativistic Heavy Ion collision experiments which √ are being performed in the STAR experiment at RHIC ( s = 200 GeV) and √ ALICE ( s = 5.5 TeV) experiment at LHC. Various observables derived from the properties of the produced particles of the interacting system. Specialized detectors are built for detection of specific types of particles. Dedicated efforts are made in data analysis studying the observables in the soft and hard sector in AA collisions which are then compared with the results form pp and dAu collisions for attaining at a consistent picture. In this thesis as a part of the detector developmental work, fabrication and testing of the Photon Multiplic- ity Detector (PMD) installed in the ALICE experiment at LHC have been discussed. A detailed√ simulation using PYTHIA with GEANT is performed with pp collision (at s = 14 TeV) events at LHC as a readiness exercise of data analysis in such collisions. In this work, we have also analyzed the STAR data for pp and dAu collisions √ at s = 200 GeV for extracting the jT , kT of jets using the method of di- hadron correlations. Transverse momentum imbalance (kT ) of the di-jets in pp collisions, by its own nature, has a special importance in characterizing the intrinsic transverse momentum of partons and its broadening in vacuum. Interaction of the hard partons in nuclear medium is expected to lead to the additional broadening in kT . Centrality dependence of jT , kT in dAu collisions have been studied with the STAR data for the first time in wide kinematic region. Comparisons have been made with the results form PYTHIA and HIJING models. Jet transverse momentum ( jt2 ) and jet acoplanarity ef- √ 2 fect ( kt ) for pp at s = 200 GeV using π 0 -ch correlation for π 0 selected in the pT range 6.5-18.5 GeV/c are found to be 598 ± 28 (stat) GeV/c and 2.80±0.04(stat)±0.27(sys) GeV/c respectively. The effect of the k T broad- ening form the dAu data is found to be 10-20%. These results will help in interpreting the results from heavy ion collisions like AuAu at RHIC illumi- nating the formation of the high-density matter. We have also performed a simulation study for γ-jet detection as a golden channel in the Photon Spec- trometer (PHOS) acceptance in ALICE. The work consists of a method of using the transverse momentum imbalance of the di-jets to enhance the purity of the direct photon detection in pp for ALICE in LHC energy.