Search for particles decaying to tt pairs through the di-lepton decay mode using the ATLAS detector at CERN

This thesis describes a selection and analysis of high mass it pairs in the di-Ieptonic decay channels. The aim of this research is to find new particles decaying to it pairs in the high mass regions of order rv 1 Te V. This is performed using the ATLAS detector at the LHC and the data collected from periods E4 - I (06/08/2010 - 29/10/2010), amounting to approximately 35 pb- 1 of usable data. The analysis achieves efficiencies of 22% to 47% in the four decay channels considered and detects a total of 105 candidate events with 91±9 events expected. The total impurity of the selected sample is between 11% and 15%. In these samples no evidence is yet seen to suggest the existence of new high mass particles decaying to tt pairs