Partonic state and single transverse spin asymmetry in Drell-Yan process
Partonic state and single transverse spin asymmetry in Drell-Yan process
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DOI：
10.1088/1126-6708/2008/11/090
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发表时间：
2008-09
影响因子：
5.4
通讯作者：
J. P. Ma;H. Sang
中科院分区：
文献类型：
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作者：
J. P. Ma;H. Sang
单横自旋不对称性在实验和理论上都得到了广泛的研究。理论上，已经提出了两种因子分解方法。一种是利用横动量相关因子分解，非对称性来自于所谓的Sivers函数。另一种方法是利用共线因子分解，其中非微扰效应由扭3强子矩阵元参数化。然而，在这两种方法中，不对称性的因式分解公式是在强子水平上通过图展开形式地导出的，其中一个工作与强子密度矩阵的各个部分。如果这两个因式分解成立，它们也应该在部分子水平上成立。我们研究这一点的Drell-Yan过程取代强子与部分子。通过计算α（s）的非平凡首阶的非对称性、Sivers函数和twist-3矩阵元，我们发现我们可以重现横动量相关因子分解的结果.但我们只能部分地验证共线分解的结果。Sivers函数和twist-3矩阵元之间的两个正式导出的关系也检查与否定的结果。
Single transverse-spin asymmetries have been studied intensively both in experiment and theory. Theoretically, two factorization approaches have been proposed. One is by using transverse-momentum-dependent factorization and the asymmetry comes from the so called Sivers function. Another is by using collinear factorization where the non- perturbative effect is parameterized by a twist-3 hadronic matrix element. However, the factorized formulas for the asymmetries in the two approaches are derived at hadron level formally by diagram expansion, where one works with various part on density matrices of hadrons. If the two factorizations hold, they should also hold at parton level. We examine this for Drell-Yan processes by replacing hadrons with partons. By calculating the asymmetry, Sivers function and the twist-3 matrix element at nontrivial leading order of alpha(s), we find that we can reproduce the result of the transverse-momentum-dependent factorization. But we can only verify the result of the collinear factorization partly. Two formally derived relations between Sivers function and the twist-3 matrix element are also examined with negative results.