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arXiv 0911.2113hep-ph
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RHIC质子-质子碰撞中瞬发J/psi的极化

Polarization of prompt J/psi in proton-proton collisions at RHIC

Hee Sok Chung, Seyong Kim, Jungil Lee, Chaehyun Yu

摘要:

在非相对论QCD(NRQCD)分解方法的框架内,我们计算了在Brookhaven相对论重离子对撞机上动量中心能量sqrt{s}=200 GeV的质子-质子碰撞产生的瞬发J/psi的极化.在强耦合常数下,计算了首阶微扰贡献。预测结果表明,色单重态的贡献严重低估了PHENIX初步数据在快度范围|y| <0.35时积分的微分截面,且色单重态的贡献是强横向极化的,这与PHENIX初步数据不一致。在考虑了色八重态的贡献后,我们发现在横动量范围1.5 GeV < p_T < 5 GeV(1.5 GeV < p_T < 2 GeV)和快度范围|y| <0.35(1.2 < |y| < 2.2)积分的NRQCD预测在误差范围内与数据一致。

英文摘要:

Within the framework of the nonrelativistic QCD (NRQCD) factorization approach, we compute the polarization of prompt J/psi produced at the Brookhaven's Relativistic Heavy-Ion Collider from proton-proton collisions at the center-of-momentum energy sqrt{s}=200 GeV. The perturbative contributions are computed at leading order in the strong coupling constant. The prediction reveals that the color-singlet contribution severely underestimates the PHENIX preliminary data for the differential cross section integrated over the rapidity range |y|<0.35 and its contribution is strongly transversely polarized, which disagrees with the PHENIX preliminary data. After including the color-octet contributions, we find that the NRQCD predictions for both the cross section and polarization over the transverse-momentum range 1.5 GeV < p_T < 5 GeV (1.5 GeV < p_T < 2 GeV) integrated over the rapidity range |y|<0.35 (1.2 < |y| < 2.2) agree with the data within errors.

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