Chinese Physics C > 2012, Vol. 36 > Issue(10): 979-984 DOI: 10.1088/1674-1137/36/10/011

Discrimination of converted photons and neutral pions at high energies

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Abstract：
In the LHC experiment, the H→ γγchannel provides a clean nal state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H→ γγchannel 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 ⁰discrimination 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 γand π ⁰, with the TMVA (Toolkit for Multivariate Data Analysis) to do the separation. With this method we can get 30% to 60% π ⁰rejection efficiency when keeping 90% converted γefficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.

References

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Aad G et al. (ATLAS collaboration). Expected Photon Performance in the ATLAS Experiment, Tech. Rep. ATL-PHYS-PUB-2011-007, CERN, Geneva[2] Nakamura K et al. (Particle Data Group). Journal of Physics G: Nuclear and Particle Physics, 2010, 37: 075021[3] Adair A et al. (CMS collaboration). J. Instrum., 2008, 3: S08004. 361[4] Bayatian G L et al. CMS Physics Technical Design Report Volume I: Detector Performance and Software, Technical Design Report CMS. Geneva: CERN, 2006[5] Awes T C, Obenshain F E, Plasil F et al. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992, 311: 130[6] TAO, Jun-Quan et al. Chin. Phys. C, 2011, 35: 269[7] Hoecker A, Speckmayer P, Stelzer J et al. 2007, ArXiv Physics e-prints[8] Grunhaus J, Kananov S. Nucl. Instrum. Methods A, 1997, 391: 351[9] Khachatryan V, Sirunyan A M, Tumasyan A et al. Phys. Rev. Lett., 2011, 106: 082001

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XIAO Hong, CHEN Guo-Ming, TAO Jun-Quan, BIAN Jian-Guo, FAN Jia-Wei, LIANG Song, MENG Xiang-Wei, SHEN Yu-Qiao, TANG Zhi-Cheng, WANG Jian, WANG Xian-You, WANG Zheng, XU Ming, XU Wei-Wei, YANG Min and YAN Qi. Discrimination of converted photons and neutral pions at high energies[J]. Chinese Physics C, 2012, 36(10): 979-984. doi: 10.1088/1674-1137/36/10/011

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Received: 2012-01-18
Revised: 2012-03-15

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通讯作者:陈斌, bchen63@163.com

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沈阳化工大学材料科学与工程学院沈阳 110142

Discrimination of converted photons and neutral pions at high energies

Corresponding author:XIAO Hong,

Received Date:2012-01-18
Accepted Date:2012-03-15
Available Online:2012-10-05

Abstract:In the LHC experiment, the H→γγchannel provides a clean nal state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H→γγchannel 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, soγ/π⁰discrimination 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 convertedγandπ⁰, with the TMVA (Toolkit for Multivariate Data Analysis) to do the separation. With this method we can get 30% to 60%π⁰rejection efficiency when keeping 90% convertedγefficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.