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arXiv 1106.5533hep-ph
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pQCD多部分子相互作用物理学

pQCD Physics of multiparton interactions

B. Blok, Yu. Dokshitser, L. Frankfurt, M. Strikman

摘要:

从提取三部分子和四部分子($3\to4$,$4\to4$)的{ \em双硬相互作用}的贡献出发,研究了%硬强子-强子碰撞中两对喷注的产生.这种相互作用,尽管在总截面的水平上被功率抑制,但当两个成对喷流的横向动量不平衡相对较小时,在{ \em背靠背运动学}中,这种相互作用变得与两个部分子$2\to4$的标准硬碰撞相当。我们通过广义两部分子分布$_2$ GPDs \cite{BDFS1}来表示双部分子碰撞中双双喷注产生的微分截面和总截面,该分布包含非微扰起源的大距离两部分子关联以及由于部分子演化引起的小距离关联。我们发现,这些大距离和小距离的相关性参与以不同的方式在4喷流的生产,并把他们在领先的对数近似的pQCD,恢复共线矩阵在所有订单。一个特别强调的是$3\to4$双硬相互作用过程中发生的相互作用之间的大和短距离的部分子的相关性,并没有考虑到的方法启发的部分子模型图片。我们证明,$3\to4$机制,在$\as$作为$4\to4$过程相同的顺序,原来是{ \em几何增强}相比,后者,应有助于显着4-射流生产。这里开发的框架系统地考虑了$_2$ GPD的微扰$Q^2$演化。它可以被用来作为一个基础,为未来的分析非线性光学修正的多部分子相互作用(MPI)在大型强子对撞机和Tevatron对撞机,特别是为改善评估QCD背景的新的物理搜索。

英文摘要:

We study production of two pairs of jets in %hard hadron--hadron collisions in view of extracting contribution of {\em double hard interactions} of three and four partons ($3\to4$, $4\to4$). Such interactions, in spite of being power suppressed at the level of the total cross section, become comparable with the standard hard collisions of two partons, $2\to4$, in the {\em back-to-back kinematics} when the transverse momentum imbalances of two pairing jets are relatively small. We express differential and total cross sections for two-dijet production in double parton collisions through the generalized two-parton distributions, $_2$GPDs \cite{BDFS1}, that contain large-distance two-parton correlations of non-perturbative origin as well as small-distance correlations due to parton evolution. We find that these large- and small-distance correlations participate in different manner in 4-jet production, and treat them in the leading logarithmic approximation of pQCD that resums collinear logarithms in all orders. A special emphasis is given to $3\to4$ double hard interaction processes that occur as an interplay between large- and short-distance parton correlations and were not taken into consideration by approaches inspired by the parton model picture. We demonstrate that the $3\to4$ mechanism, being of the same order in $\as$ as the $4\to4$ process, turns out to be {\em geometrically enhanced} compared to the latter and should contribute significantly to 4-jet production. The framework developed here takes into systematic consideration perturbative $Q^2$ evolution of $_2$GPDs. It can be used as a basis for future analysis of NLO corrections to multi-parton interactions (MPI) at LHC and Tevatron colliders, in particular for improving evaluation of QCD backgrounds to new physics searches.

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