Fast computation of observed cross section for ψ′ → PP decays  

作　　者：王博群 莫晓虎 王平 班勇 

机构地区：[1]School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University [2]Institute of High Energy Physics, Chinese Academy of Sciences

出　　处：《Chinese Physics C》2011年第5期411-418,共8页中国物理C（英文版）

基　　金：Supported by National Natural Science Foundation of China (10491303, 10775412, 10825524, 10835001, 10935008);Instrument Developing Project of Chinese Academy of Sciences (YZ200713);Major State Basic Research Development Program (2009CB825200, 2009CB825206);Knowledge Innovation Project of Chinese Academy of Sciences (KJCX2-YW-N29)

摘　　要：It has been conjectured that the relative phase between strong and electromagnetic amplitudes is universally -90° in charmonium decays. ψ′ decaying into a pseudoscalar pair provides a possibility to test this conjecture. However, the experimentally observed cross section for such a process is depicted by the two-fold integral, which takes into account the initial state radiative （ISR） correction and energy spread effect. Using the generalized linear regression approach, a complex energy-dependent factor is approximated by a linear function of energy. Taking advantage of this simplification, the integration of ISR correction can be performed and an analytical expression with accuracy at the level of 1% is obtained. Then, the original two-fold integral is simplified into a one-fold integral, which reduces the total computing time by two orders of magnitude. Such a simplified expression for the observed cross section usually plays an indispensable role in the optimization of scan data taking, the determination of systematic uncertainty, and the analysis of data correlation.It has been conjectured that the relative phase between strong and electromagnetic amplitudes is universally -90° in charmonium decays. ψ′ decaying into a pseudoscalar pair provides a possibility to test this conjecture. However, the experimentally observed cross section for such a process is depicted by the two-fold integral, which takes into account the initial state radiative （ISR） correction and energy spread effect. Using the generalized linear regression approach, a complex energy-dependent factor is approximated by a linear function of energy. Taking advantage of this simplification, the integration of ISR correction can be performed and an analytical expression with accuracy at the level of 1% is obtained. Then, the original two-fold integral is simplified into a one-fold integral, which reduces the total computing time by two orders of magnitude. Such a simplified expression for the observed cross section usually plays an indispensable role in the optimization of scan data taking, the determination of systematic uncertainty, and the analysis of data correlation.

关 键 词：cross section narrow resonance pseudoscalar pair e ＋ e - collider 

分 类 号：O571.3[理学—粒子物理与原子核物理]