QCD Background Estimation From Data for Supersymmetry Searches at ATLAS

A major challenge in the search for Supersymmetry (SUSY) with no leptons at ATLAS is the measurement of the background from QCD multi-jet production. A data-driven estimation is very important for this background; it is difficult to accurately estimate jet response tails using Monte Carlo (MC) simulation and furthermore it is impossible to generate sufficient MC simulated QCD events, given the high QCD cross section. The jet smearing method is a fully data-driven technique which uses a measurement of the jet response function to estimate the QCD background to SUSY through the 'smearing' of seed events. The technique has been validated using MC simulation and is now being used on ATLAS data.