Study of jets in Heavy Ion collisions using the ATLAS detector

The measurement of jets and their properties provides information about the jet quenching phenomenon that is predicted for heavy ion collisions and already measured at RHIC. At LHC energies where the jets are more pronounced above the background, the full jet reconstruction can be used. The jet quenching means that a hard parton, before fragmenting into a jet of hadrons, deposits a fraction of its energy in the medium, leading to a change of jet energy distribution and particle multiplicity inside a jet. This allows us to investigate the properties of medium and its response to a traversing parton. We present studies of the performance of a cone and fast-kT jet reconstruction algorithms with full GEANT simulation of the ATLAS detector. Simulated jets from PYTHIA are embedded to the heavy ion background from HIJING. The study shows results of the jet energy and position resolutions of the ATLAS calorimeter system for different centralities of the PbPb collision. We present ATLAS capability for measurement of jet energy profiles, j_T distributions and fragmentation functions. The possible modification of these quantities simulated by the Pyquen program is also presented. We present the study of the di-jet observables.