Pile-up subtraction and suppression for jets in ATLAS

An improved pile-up correction for jets in ATLAS, based on the concept of the jet area, is described and evaluated. The method corrects the jet transverse momentum and inherently accommodates jet-by-jet variations in pile-up sensitivity as well as event-by-event fluctuations in pile-up activity. The parameters for the method are optimized in simulation, and its performance is validated using in-situ methods in 2012 data, from which systematic uncertainties are also estimated. The resulting fractional uncertainty in the jet \pt{} scale is typically less than $2 \%$ for jets with $\pt > 50$ \GeV{} across the full coverage of the detector, with significantly lower uncertainties for central jets. A track-based method for the suppression of pile-up jets is also presented, using the jet vertex fraction (JVF). The dependence of JVF on jet kinematics, jet flavor, and pile-up is discussed, and the performance of JVF as a discriminating variable is assessed in both 2012 data and simulation. Finally, a method to address mis-modeling in JVF is presented, with recommended systematic variations in specific JVF cut values.