arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0707.2643hep-ph
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新的QCD现象

Novel QCD Phenomena

Stanley J. Brodsky

摘要:

我讨论了一些新的主题在QCD,包括使用的AdS/CFT对应Anti-de Sitter空间和共形规范理论,以获得一个易于分析的近似QCD的制度,其中QCD耦合是大的和恒定的。特别是,在AdS空间的第五维坐标z和一个特定的影响变量zeta之间存在着精确的对应关系,该变量zeta测量了普通时空中强子内夸克成分的分离。这种联系使我们能够计算介子和重子的独立于标架的光阵面波函数的解析形式,介子和重子是编码强子性质的基本实体,并允许计算唯一的散射振幅。我还讨论了QCD的一些新的唯象学特征。在部分子模型中通常被忽略的胶子交换的初态和终态相互作用在QCD硬散射反应中有着深远的影响,导致了主导扭转单自旋不对称,衍射深度非弹性散射,衍射硬强子反应,Drell-Yan反应中Lam Tung关系的破裂,以及核遮蔽和非普适反遮蔽-领先扭曲物理学没有被纳入孤立计算的目标的光阵面波函数中。我还讨论了核波函数中隐藏颜色的测试,利用衍射实现强子抛射体的Fock态和测试QCD颜色透明度,以及异常重夸克效应。在硬子过程中产生质子的直接高扭曲过程的存在可以解释在高中心性重离子碰撞中看到的大质子-π介子比。

英文摘要:

I discuss a number of novel topics in QCD, including the use of the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. In particular, there is an exact correspondence between the fifth-dimension coordinate z of AdS space and a specific impact variable zeta which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. I also discuss a number of novel phenomenological features of QCD. Initial- and final-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and anomalous heavy quark effects. The presence of direct higher-twist processes where a proton is produced in the hard subprocess can explain the large proton-to-pion ratio seen in high-centrality heavy-ion collisions.

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