Search for the Standard Model Higgs boson in Z + gamma final states with the ATLAS detector at the LHC.

摘要

This dissertation describes a search for the Standard Model Higgs boson in Z+photon channel with the ATLAS detector at the LHC using 4.6 fb-1 of proton-proton collisions at center of mass energy 7 TeV in 2011 and 20.7 fb-1 of proton-proton collisions at center of mass energy 8 TeV in 2012. The distribution of the mass difference between MZphoton and MZ is compared to the Standard Model (SM) background expectations. No significant deviation from the SM prediction is observed and the upper limits on the signal strength mu of a Higgs boson with a mass between 120 and 150 GeV are derived. The expected exclusion limits at 95% confidence level range between 7.3 and 22.3 times the predicted Standard Model cross section. The observed exclusion limits range between 5.3 and 38.7 times the Standard Model cross section. For a Higgs boson with mass of 125.5 GeV, the expected and observed limits are 13.2 and 17.0 times the Standard Model respectively.