Quark and Gluon Jet Response from Dijet and Z + Jet Events at ATLAS

Synopsis

The most common objects produced in proton-proton collisions at Large Hadron Collider (LHC) are jets, collimated sprays of particles representing an initial quark or gluon from the collision. Jet response is the fraction of jet energy measured by the detector, determined through jet calibration. Jets initiated by quarks and gluons develop differently and thus have different responses. This thesis determines the responses of quark and gluon initiated jets by comparing two different event types, two back-to-back jets (dijet) and Z-boson plus one jet (Z + jet). A method is developed to calibrate dijet events using the same technique as Z + jet events, and is shown to be successful. The responses of quark and gluon jets are calculated, and while the quark jet response behaves as expected, the gluon jet response does not. Additional examination reveals why the gluon response may be flawed and how it can be improved in future research.