Optimization of the Level 2 electron-photon Trigger within ATLAS
This report outlines preliminary studies performed into the optimization of the ATLAS Level 2 electron-photon egamma trigger with respect to the 2010 data run. Electrons from Z decay are a major source of high pT electrons, an understanding of which is vital for many physics analyses. This optimization focuses on electrons from Z decay. The optimization procedure identifies signal (actual electrons) and background (mis-identified electrons) Level 2 trigger electrons using geometrical matching. Reducing the number of these background trigger electrons has obvious benefits with respect to data storage. A number of possible variables useful in discriminating this signal from background are identified. A log-likelihood ratio discriminant method is developed based on these variables and tested using Monte Carlo. The performance is cross checked using 2010 data. The log-likelihood discriminant method is compared with a cuts based method, based on individual variables and is shown to give improved results.
