CERN Accelerating science

In ultra-relativistic heavy-ion (AA) collisions, a high density decon ned state of quarks and gluons is produced which is known as the Quark Gluon Plasma (QGP). This state of matter is supposed to have existed microseconds after the Big Bang and resemble the state of the early universe. Attempts have been made to produce this system over a wide range of energy and/or energy-density using facilities such as the Relativistic Heavy Ion Collider (RHIC), the Large Hadron Collider (LHC). This produced system is very short lived and the main challenge of this eld of research is to characterise this short lived state of matter. There are few proposed signals to probe the QGP and a family of such probes are termed as the hard probes which are produced at the early stage of the collision and are considered to be the novel probes for the QGP medium. The massive available collision energy at the LHC makes it possible to produce hard probes with increased cross-sections. Jets belong to the family of such hard probes. A jet is the concentrated collection of hadrons, produced from the fragmentation of a hard scattered parton. In heavy-ion collisions, a decon ned dense medium of free partons is created and the hard initial partons lose their energy while traversing through the medium by the interaction with the medium's partons. This phenomena is termed "jet quenching" and is a smoking gun signature of the QGP production. Though the study of heavy-ion collisions is at the heart of this eld, there is also the need for baseline references (in vacuum) to re ect the e ects of the medium properly. Study of proton- proton (pp) collisions serves this purpose. The pp collision is also signi cant in it's own term for providing the testing ground for pQCD processes. The jet study in pp collisions, provides detailed insight on parton fragmentation. In this thesis, a jet properties study done with ALICE pp data at 2.76 TeV has been presented. The data measurements have also been compared with those obtained from Monte Carlo models to show the agreement with theory predictions. Jet properties study in heavy-ion collisions has also been conducted using the Pb-Pb events generated in the framework of a dynamical jet quenching model, JEWEL. Jet medium interactions have been investigated and the performance of the model against available experimental measurements have been presented in this thesis.