Study of the ATLAS Tile-Cal performance: Precise determination of the top mass

A new very promising method for the top mass reconstruction in ATLAS is presented. The method uses a special sub-sample of the single lepton plus jet events where the top has high pt (pt>200 Gev), available with acceptable statistics at LHC due to the high ttbar production rate. The top mass is reconstructed as the invariant mass of all the calorimeter towers in a cone around the top quark direction. From studies made with both the fast and full detector simulation programs, it is shown that an accuracy of 1-1.5 in the reconstructed top quark mass can be achieved, using only one year's data at low luminosity of LHC (10 invfb). A detailed study of the systematic errors involved with the measurement is discussed as well.