Pai-hsien Hsu

We present the first measurement of Z → ee production cross section, in proton-proton collisions at center-of-mass energy [special characters omitted] = 7 TeV, with ∼300 nb⁻¹ of data from the ATLAS detector at the LHC. This is one of the most important signatures from the Standard Model, because the properties of the Z bosons are well-measured in previous experiments and thus can be utilized to calibrate detector performance at the early stage of the LHC. The result is consistent with the theoretical prediction within uncertainties. We then describe our specific work on the performance of the Transition Radiation Tracker (TRT) using Z → ee data, and background suppression with Electromagnetic Calorimeter Timing information. We also discuss how these studies will impact on the search for the Higgs boson and signatures from other new physics beyond the Standard Model.