arXiv 1111.49962011-11hep-phhep-ex

低q_T下Drell-Yan分解定理及光锥上的横动量分布

Factorization Theorem For Drell-Yan At Low q_T And Transverse-Momentum Distributions On-The-Light-Cone

Miguel G. Echevarria, Ahmad Idilbi, Ignazio Scimemi

备注：: Minor changes. Version published in JHEP
发表信息：: JHEP07(2012)002
DOI：: 10.1007/JHEP07(2012)002

摘要：

利用有效场论方法，得到了低qT下Drell-Yan过程的一个分解定理.在这个定理中，所有得到的量都是规范不变的，并且强调了软函数及其减法的特殊作用。我们定义了横向动量相关的部分子分布函数（TMDPDF），它是自由的光锥奇点，而所有的威尔逊线被定义在光锥上。我们在α_s中明确地表明，部分子费曼PDF可以从新定义的部分子TMDPDF中通过对强子内部部分子的横向动量进行积分来获得。在碰撞参量空间中，我们得到了TMDPDF的图解表达式，从而得到了横截面的图解表达式。新定义的矩阵元的普适性在α_s中被微扰到一阶。在α s中证明了因式分解定理的一阶性，并证明了费曼规范与光锥规范之间的规范不变性。

英文摘要：

We derive a factorization theorem for Drell-Yan process at low q_T using effective field theory methods. In this theorem all the obtained quantities are gauge invariant and the special role of the soft function--and its subtraction thereof--is emphasized. We define transverse-momentum dependent parton distribution functions (TMDPDFs) which are free from light-cone singularities while all the Wilson lines are defined on-the-light-cone. We show explicitly to first order in α_s that the partonic Feynman PDF can be obtained from the newly defined partonic TMDPDF by integrating over the transverse momentum of the parton inside the hadron. We obtain a resummed expression for the TMDPDF, and hence for the cross section, in impact parameter space. The universality of the newly defined matrix elements is established perturbatively to first order in α_s. The factorization theorem is validated to first order in α_s and also the gauge invariance between Feynman and light-cone gauges.

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