Studies of a top quark mass measurement in the dilepton channel using the m_{T2} variable at ATLAS

A measurement of the top quark mass in the dilepton channel is studied. A mass measurement in the dilepton channel is challenging, due to the production of two neutrinos. In order to circumvent this difficulty, the m_{T2} variable is used. The m_{T2} variable is used in pair production events with two missing particles and represents a lower bound to the parent particles mass. The mass measurement is based on the calibration curve method, with pp collision data at the LHC, measured with the ATLAS detector. Applying this method on 2 fb−1 ATLAS data, a measurement of the top mass was made, giving a value of 172.7 ± 1.4_{−4.6 GeV}^{+ 4.2}. This measurement is dominated by the systematic uncertainty, with the jet energy scale systematic uncertainty giving the strongest contribution. The jet energy scale systematic uncertainty was reduced by combining the mass measurement using leptons m_{T2} with a mass measurement performed with p_{T}. An improvement in the value of the systematic uncertainty is achieved with this measurement combination, yielding a top quark mass value of 172.9 ± 1.2_{-4.0}^{+3.4} GeV.