Discrimination of converted photons and neutral pions at high energies  

作　　者：肖虹 陈国明 陶军全 卞建国 范嘉伟 梁松 孟祥伟 沈玉乔 唐志成 王健 王健 汪先友 王征 徐明 许伟伟 杨民 严琪 

机构地区：[1]Institute of High Energy Physics, Chinese Academy of Sciences [2]Graduate University of Chinese Academy of Sciences [3]Theoretical Physics Institute, Chongqing University

出　　处：《Chinese Physics C》2012年第10期979-984,共6页中国物理C（英文版）

基　　金：Supported by Natural Science Foundation of China (10435070, 10773011, 10721140381, 10099630);China Ministry of Science and Technology (2007CB16101, 2010CB833000)

摘　　要：In the LHC experiment, the H →γγ channel provides a clean final state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H →γγ channel is one of the most promising channels for the Higgs discovery in the very low mass region. In order to increase the sensitivity of the Higgs search, background rejection rate is very important, so γ/π 0 discrimination is one of the key points in the analysis. At least 40% of photons will convert with the experience of ATLAS and CMS. We constructed electromagnetic calorimeter （ECAL） in GEANT4 simulation, using 6 variables which have different shapes between converted γ and π 0 , with the TMVA （Toolkit for Multivariate Data Analysis） to do the separation. With this method we can get 30% to 60% π 0 rejection efficiency when keeping 90% converted γ efficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.In the LHC experiment, the H →γγ channel provides a clean final state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H →γγ channel is one of the most promising channels for the Higgs discovery in the very low mass region. In order to increase the sensitivity of the Higgs search, background rejection rate is very important, so γ/π 0 discrimination is one of the key points in the analysis. At least 40% of photons will convert with the experience of ATLAS and CMS. We constructed electromagnetic calorimeter （ECAL） in GEANT4 simulation, using 6 variables which have different shapes between converted γ and π 0 , with the TMVA （Toolkit for Multivariate Data Analysis） to do the separation. With this method we can get 30% to 60% π 0 rejection efficiency when keeping 90% converted γ efficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.

关 键 词：converted γ π 0 DISCRIMINATION TMVA 

分 类 号：O572.3[理学—粒子物理与原子核物理]