Underlying-Event Subtraction for Particle Flow

CMS uses currently a preclustering into fixed tower geometry and jet reconstruction on the subtracted event. A new underlying event subtraction algorithm is presented to allow to subtract the soft scale on a full particle flow event, where the resulting hard event can be directly reconstructed by jet reconstruction. The performance is studied using fully GEANT simulated PYTHIA events embedded into HYDJET PbPb underlying event. We compared the performance of the new algorithm against the current CMS iterative pile-up algorithm, and the FastJet $\rho$A global rescaled subtraction.