Light-quark and Gluon Jets in ATLAS

The jet energy response depends on the observable properties of a jet, including, for example, the momentum spectra and number of charged hadrons. The fragmentation differences between jets initiated by a quark and jets initiated by a gluon lead to a flavor dependence in the jet energy scale. Because the flavor content of samples varies, this difference results in an additional flavor-dependent term in the jet energy scale uncertainty. This term is derived for a general sample of jets and can be up to ~8% in cases where the flavor composition of a sample of events is poorly known. A template-fit method for determining the flavor composition of a sample of jets is presented. The templates, based on jet properties sensitive to the partonic origin of the jet, allow the determination of flavor composition with a precision of about 10%. The flavor-dependent term of the jet energy scale systematic uncertainty is correspondingly reduced.