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arXiv 1708.07533hep-phnucl-exnucl-th
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夸克在色场中的弹性散射:纵向动量交换

Elastic scattering of a quark from a color field: longitudinal momentum exchange

Jamal Jalilian-Marian

摘要:

小Bjorken $x$极限下的微扰QCD可以被表述为一种有效的理论,称为彩色玻璃凝聚体(CGC)形式主义。CGC形式考虑了小$x$上大胶子密度的动力学,并已成功地应用于小$x$运动学区域的高能强子和核碰撞中的深非弹性散射(DIS)和粒子产生。CGC中的有效自由度是Wilson线,它进入有效夸克(和胶子)传播子,并从目标的小$x$胶子场恢复多次软散射。然而,它是已知的,CGC有效的理论打破了当一个探针的中等大的$x$(高$p_t$)的运动学共线因式分解和DG演化的部分子分布函数应该是正确的框架。在这里,我们提出了一个一般的框架,它可能允许一个最终统一的两种方法,并计算pQCD截面在小和大的Bjorken $x$地区。我们朝着这个目标迈出了第一步,推导出一个表达式的夸克传播子在背景场,其中包括散射从小和大$x$模式的胶子场的目标。我们描述了如何用这种夸克传播子来计算QCD结构函数$F_2$和$x$,从而推广了DIS的偶极模型。本文对高能强子碰撞和核碰撞的正向快度区中的粒子产生进行了一种称为混合方法的研究,并将其应用于所有的$x$和$p_t$区,并推测如何应用同样的方法将用于高能重离子碰撞的McLerran-Venugopalan有效作用量扩展到包括高$p_t$物理。

英文摘要:

Perturbative QCD in the small Bjorken $x$ limit can be formulated as an effective theory known as the Color Glass Condensate (CGC) formalism. The CGC formalism takes into account the dynamics of large gluon densities at small $x$ and has been successfully applied to Deep Inelastic Scattering (DIS) and particle production in high energy hadronic and nuclear collisions in the small $x$ kinematic region. The effective degrees of of freedom in CGC are Wilson lines which enter in the effective quark (and gluon) propagators and re-sum multiple soft scatterings from the small $x$ gluon field of the target. It is however known that the CGC effective theory breaks down when one probes the moderately large $x$ (high $p_t$) kinematics where collinear factorization and DGLAP evolution of parton distribution functions should be the right framework. Here we propose a general framework which may allow one to eventually unify the two approaches and to calculate pQCD cross sections in both small and large Bjorken $x$ regions. We take the first step towards this goal by deriving an expression for the quark propagator in a background field which includes scatterings from both small and large $x$ modes of the gluon field of the target. We describe how this quark propagator can be used to calculate QCD structure functions $F_2$ and $F_L$ at all $x$ and thus generalize the dipole model of DIS. We outline this approach can also be used to extend the so-called hybrid approach to particle production in the forward rapidity region of high energy hadronic and nuclear collisions to all $x$ and $p_t$ regions and speculate on how one may apply the same techniques to extend the McLerran-Venugopalan effective action used in high energy heavy ion collisions to include high $p_t$ physics.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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