Three-gluon contribution to the single spin asymmetry in Drell-Yan and direct-photon processes
Three-gluon contribution to the single spin asymmetry in Drell-Yan and direct-photon processes
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DOI：
10.1103/physrevd.85.034030
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发表时间：
2011-12
影响因子：
5
通讯作者：
Y. Koike;S. Yoshida
中科院分区：
文献类型：
--
作者：
Y. Koike;S. Yoshida
我们导出了由横向极化核子中的twist-3三胶子相关函数相对于QCD耦合常数处于领先顺序引起的$pp$碰撞中Drell-Yan轻子对产生和直接光子产生的单自旋相关截面。结合文献中的twist-3夸克-胶子相关函数的贡献，这完成了这些过程的twist-3横截面。我们还提出了相对论重离子对撞机（RHIC）能量下直接光子产生的不对称性的模型计算，证明了不对称性对三胶子相关函数形式的敏感性。特别是，我们表明极化核子向后方向的不对称性是由相关函数的小$x$行为决定的。
We derive the single-spin-dependent cross section for the Drell-Yan lepton-pair production and the direct-photon production in the $pp$ collision induced by the twist-3 three-gluon correlation functions in the transversely polarized nucleon in the leading order with respect to the QCD coupling constant. Combined with the contribution from the twist-3 quark-gluon correlation functions in the literature, this completes the twist-3 cross section for these processes. We also present a model calculation of the asymmetry for the direct-photon production at the relativistic heavy ion collider (RHIC) energy, demonstrating the sensitivity of the asymmetry to the form of the three-gluon correlation functions. In particular, we show that the asymmetry in the backward direction of the polarized nucleon is determined by the small-$x$ behavior of the correlation functions.