Accounting for Jet Response Induced / E T Backgrounds to New Physics at the Atlas Experiment at Cern's Lhc

Detector mis-modelling or hardware problems may cause an excess of Missing Transverse Energy ( / ET ) to be inferred in physics events recorded in ATLAS, leading to higher than expected backgrounds for new physics. In particular, non-Gaussian tails in the / ET distribution are unlikely to be well modelled in Monte Carlo simulations. To account for this, a technique has been established to improve the background predictions derived from Monte Carlo simulations. This is done using a correction derived through comparison of control samples in data and Monte Carlo simulation. Two different control samples are used to create the correction, giving a range of predictions for the shape of the / ET tail and aiding the calculation of systematic errors. This technique is then applied to several samples which are potential backgrounds to new physics which give detector signatures which include / ET .