Measurement of the jet energy resolution in ATLAS

The jet energy resolution can be determined in in-situ from the measurement of the transverse momentum balance of a system of two jets (transverse momentum asymmetry). The measurement is based on the direct transverse momentum balance and a decomposition of the transverse jet momentum along the bi-sector of the two jets. Good agreement between data and Monte Carlo simulations is found. Sophisticated jet calibration schemes based on cell energy weighting or exploiting the internal jet structure are also presented. Such calibration schemes improve the jet resolution by 20-30% and in addition reduce the flavour dependence of the jet response.