Extract Signals by Fitting χ<SUP>2</SUP> Distribution of the Kinematic Fit

PING Rong-Gang; MO Xiao-Hu; DU Shu-Xian; LIU Jing; MA Lian-Liang; SHEN Cheng-Ping; WANG Zhi-Yong; YUAN Chang-Zheng

Chinese Physics C> 2007, Vol. 31> Issue(3) : 229-231

Extract Signals by Fitting χ² Distribution of the Kinematic Fit

Institute of High Energy Physics, CAS, Beijing 100049, China

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Abstract：
In measuring the ψ(2S) radiative decays at BESⅡ, contribution of the background is serious in most of the final states. To extract the number of signal events, a fit to the χ² distribution of kinematic fit using signal and background components is proposed. Extensive Monte-Carlo simulations (MCS) are performed, and the results show that the shape of χ² distribution of the signal channel looks different from those of the background channels, thus it provides us by fitting the χ² distribution of the data to extract the number of signal events. An input-output test is performed using MCS, and the uncertainty of the fit method is found to be less than 2%.
References

[1] . Particl Data Group. Phys. Lett., 2004, B592: 612. Ablikim M et al(BES Collab.). Nucl. Instrum. Methods,2005, A552: 344

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PING Rong-Gang, MO Xiao-Hu, DU Shu-Xian, LIU Jing, MA Lian-Liang, SHEN Cheng-Ping, WANG Zhi-Yong and YUAN Chang-Zheng. Extract Signals by Fitting χ² Distribution of the Kinematic Fit[J]. Chinese Physics C, 2007, 31(3): 229-231.

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Received: 2006-07-10
Revised: 2006-08-17

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沈阳化工大学材料科学与工程学院沈阳 110142

Extract Signals by Fitting χ² Distribution of the Kinematic Fit

Corresponding author: PING Rong-Gang,

Institute of High Energy Physics, CAS, Beijing 100049, China

Received Date: 2006-07-10
Accepted Date: 2006-08-17
Available Online: 2007-03-05

Abstract: In measuring the ψ(2S) radiative decays at BESⅡ, contribution of the background is serious in most of the final states. To extract the number of signal events, a fit to the χ² distribution of kinematic fit using signal and background components is proposed. Extensive Monte-Carlo simulations (MCS) are performed, and the results show that the shape of χ² distribution of the signal channel looks different from those of the background channels, thus it provides us by fitting the χ² distribution of the data to extract the number of signal events. An input-output test is performed using MCS, and the uncertainty of the fit method is found to be less than 2%.