Application of the parametric for mulae for electromagnetic showers in unconverted γ/π~0 discrimination  

作　　者：陶军全 陈国明 杨民 卞建国 李祖豪 梁松 孟祥伟 唐志成 王健 王健 汪先友 王征 肖虹 徐明 藏京京 张振霞 

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》2011年第3期269-277,共9页中国物理C（英文版）

基　　金：Supported by National Natural Science Foundation of China (10435070, 10721140381, 10099630);China Ministry of Science and Technology (2007CB16101);Chinese Academy of Sciences (KJCX2-N17, 1730911111)

摘　　要：In the LHC experiment, the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state. In this paper, the application of the three-dimensional parametric formula for electromagnetic （EM） showers, which we developed in the Alpha Magnetic Spectrometer II experiment, is presented to distinguish the unconverted photons from the neutral pions. With the constructed electromagnetic calorimeter （ECAL） in a GEANT4 simulation, the parametric formulae were validated and the unconverted γ/π0 discrimination was performed with the Toolkit for Multivariate Data Analysis （TMVA） package in ROOT for different transverse energies ranging from 15 GeV to 75 GeV, which is the most sensitive region for light Higgs （with mass ～120 GeV） searches with the channel H → γγ. With this discrimination method and the selected transverse energy region, we can reject π0 with the effciency from ～ 40% （65–75 GeV） to ～ 90% （15–25 GeV） when keeping 90% γ effciency.In the LHC experiment, the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state. In this paper, the application of the three-dimensional parametric formula for electromagnetic （EM） showers, which we developed in the Alpha Magnetic Spectrometer II experiment, is presented to distinguish the unconverted photons from the neutral pions. With the constructed electromagnetic calorimeter （ECAL） in a GEANT4 simulation, the parametric formulae were validated and the unconverted γ/π0 discrimination was performed with the Toolkit for Multivariate Data Analysis （TMVA） package in ROOT for different transverse energies ranging from 15 GeV to 75 GeV, which is the most sensitive region for light Higgs （with mass ～120 GeV） searches with the channel H → γγ. With this discrimination method and the selected transverse energy region, we can reject π0 with the effciency from ～ 40% （65–75 GeV） to ～ 90% （15–25 GeV） when keeping 90% γ effciency.

关 键 词：electromagnetic shower parametric formulae γ/π0 discrimination 

分 类 号：O572.31[理学—粒子物理与原子核物理]