High-Energy Photon-Hadron Scattering in Holographoic QCD
High-Energy Photon-Hadron Scattering in Holographoic QCD
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全息 QCD 中的高能光子-强子散射
DOI：
10.1103/physrevd.84.075025
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
Taizan Watari
中科院分区：
文献类型：
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作者：
Ryoichi Nishio;Taizan Watari
本文通过使用强耦合规范理论的重力对偶描述，深入研究强子高能散射。就像深度非弹性散射（DIS）和深度虚拟康普顿散射（DVCS）作为强子非微扰内部结构的干净实验探针一样，重力对偶中的强子和（虚拟）光子的弹性散射幅度也可以用作理论探针。由于即使在强耦合状态下，足够高能量（小 Bjorken）下的散射幅度也由部分子贡献（<?format ?>=<?format ?>Pomeron 贡献）主导，因此有机会通过使用引力对偶模型来学习广义部分子分布 (GPD)。我们首先对引力对偶中的 Brower-Polchinski-Strassler-Tan (BPST) Pomeron 核进行精化推导，特别关注复数自旋变量所起的作用。扭曲时空上的 BPST Pomeron 由具有非线性轨迹的 4D Pomeron 的 Kaluza-Klein 塔组成，我们阐明了 Pomeron 耦合与 Pomeron 形状因子之间的关系。我们强调，复平面表示中散射幅度的鞍点值是理解散射幅度的定性行为的一个非常重要的概念。 Pomeron 对散射的总贡献被分解为鞍点贡献和至多有限数量的极点贡献，当极点贡献不存在时（我们称之为鞍点相位），ln(1/q) 演化和 ln(1/x) 演化参数以及 HERA 实验中 DIS 和 DVCS 的斜率参数的运动学变量依赖性都在重力对偶中定性地再现。所有这些观察结果都为 GPD 建模提供了新的思路。还讨论了这些结果在其他强子高能散射中的直接应用。
This article provides an in-depth look at hadron high-energy scattering by using gravity dual descriptions of strongly coupled gauge theories. Just like deeply inelastic scattering (DIS) and deeply virtual Compton scattering (DVCS) serve as cleanexperimentalprobes into nonperturbative internal structure of hadrons, elastic scattering amplitude of a hadron and a (virtual) photon in gravity dual can be exploited as atheoreticalprobe. Since the scattering amplitude at sufficiently high energy (small Bjorken) is dominated by parton contributions (<?format ?>=<?format ?>Pomeron contributions) even in strong coupling regime, there is a chance to learn a lesson for generalized parton distribution (GPD) by using gravity dual models. We begin with refining derivation of the Brower–Polchinski–Strassler–Tan (BPST) Pomeron kernel in gravity dual, paying particular attention to the role played by the complex spin variable. The BPST Pomeron on warped spacetime consists of a Kaluza–Klein tower of 4D Pomerons with nonlinear trajectories, and we clarify the relation between Pomeron couplings and the Pomeron form factor. We emphasize that the saddle-point valueof the scattering amplitude in the complex-plane representation is a very important concept in understanding qualitative behavior of the scattering amplitude. The total Pomeron contribution to the scattering is decomposed into the saddle-point contribution and at most a finite number of pole contributions, and when the pole contributions are absent (which we call saddle-point phase), kinematical variable-dependence of ln(1/q) evolution and ln(1/x) evolution parametersandin DIS and-slope parameterof DVCS in HERA experiment are all reproduced qualitatively in gravity dual. All of these observations shed a new light on modeling of GPD. Straightforward application of those results to other hadron high-energy scattering is also discussed.