Using boosted decision trees for tau identification in the ATLAS experiment

The ATLAS detector will begin taking data from p - p collisions in 2009. This experiment will allo w for man y dif ferent physics measurements and searches. The production of tau leptons at the LHC is a key signature of the decay of both the standard model Higgs (via H ! t t ) and SUSY particles. Taus have a short lifetime ( c t = 87 m m) and decay hadroni- cally 65% of the time. Man y QCD interactions produce similar hadronic sho wers and have cross-sections about 1 billion times lar ger than tau production. Multi variate techniques are therefore often used to distinguish taus from this background. Boosted Decision Trees (BDTs) are a machine-learning technique for developing cut-based discriminants which can signicantly aid in extracting small signal samples from overwhelming backgrounds. In this study , BDTs are used for tau identication for the ATLAS experiment. The y are a fast, exible alternati ve to existing discriminants with comparable or better performance.