Prospects for top quark mass measurement through the fully Hadronic decay of top-antitop events with the ATLAS detector

Abstract

This thesis outlines the prospects for top quark mass measurement through the Fully Hadronic decay of top-antitop events with the ATLAS detector. Methods with and without b-tagging were explored. Without b-tagging the signal was hidden beneath the QCD multi-jet background and prospects for a mass measurement do not appear to be good. A standard and a pessimistic b-tagging likelihood significance value were explored. The standard value gives a S/B of 0.88 and the more pessimistic value gives a S/B of 0.79. For 1 fb−1 a significance of 36.8 and 32.0 can be obtained for the standard and pessimistic scenarios respectively. A selection efficiency of 1.4% and 1.1% can be achieved for the standard and pessimistic values respectively. Assuming a top mass of 174 GeV, a mass peak can clearly be seen for both b-tagging

values. For the standard scenario, a top mass of 168.94 GeV with a statistical error of 0.33 GeV can be extracted. With the pessimistic scenario, the extracted mass is 169.11 GeV with a statistical error of 0.36 GeV. This is the first attempt with fully simulated events and therefore there are possibilities for improvement. This analysis did not include b-jet energy scale correction.