Acta Scientiarum Naturalium Universitatis Pekinensis

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A Method for Measuring J/Ψ Polarization in Hadron Collisions

HU Zhen1, GUO Shuang1, Eric James2, QIAN Sijin1   

  1. 1. State Key Laboratory of Nuclear Science and Technology, Peking University, Beijing 100871; 2. Fermi National Accelerator Laboratory, Batavia IL 60510;
  • Received:2010-03-05 Online:2011-05-20 Published:2011-05-20


胡震1,郭爽1,Eric James2,钱思进1   

  1. 1. 核物理国家重点实验室, 北京大学, 北京 100871; 2. Fermi National Accelerator Laboratory, Batavia IL 60510;

Abstract: The authors describe a method for measuring the polarization of prompt J/Ψ mesons produced in proton-proton collisions at the center of mass energy s = 10 TeV (and above) as a function of the J/Ψ transverse momentum. This measurement can be made with ~50 pb-1 of data to be collected by the CMS detector during the first period of LHC operations. The authors study potential biases in the fit procedure used to extract the polarization parameter α, and to determine the expected measurement sensitivity. The precision of the method is limited by statistics and systematic uncertainties, and is estimated about αstat < 0.13, αsyst < 0.01. This measurement is expected to provide some insight into the currently observed disagreement between the non-relativistic QCD theory and the recent J/Ψ polarization measurements by CDF on the Tevatron collider at Fermilab.

Key words: polarization, J/Ψ, B-hadron, CMS, templates, non-relativistic QCD

摘要: 描述测量 J/Ψ介子极化的方法,该方法能够测量质心能量为 10 TeV(或以上)的质子对撞中产生的 J/Ψ 介子的极化参量随其横向动量的变化, LHC 上的 CMS 探测器收集到的前 50 pb-1 的数据就可以完成这项测量。研究了用于提取极化参量α 的拟合过程的误差,并分析了相应的测量精度。该方法的测量精度受到统计误差和系统误差的影响, 其量级为αstat < 0.13, αsyst < 0.01。在费米实验室的 CDF 实验上曾进行过 J/Ψ极化的测量, 其结果与非相对论 QCD 理论预言不符,在 CMS 上进行的再次测量将为这项研究提供更充足的信息。

关键词: 极化, J/Ψ, B强子, CMS, 模板, 非相对论QCD

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