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QCD constituent counting rules for neutral vector mesons

机译：中性矢量介子的QCD成分计数规则

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QCD constituent counting rules define the scaling behavior of exclusive hadronic scattering and electromagnetic scattering amplitudes at high momentum transfer in terms of the total number of fundamental constituents in the initial and final states participating in the hard subprocess. The scaling laws reflect the twist of the leading Fock state for each hadron and hence the leading operator that creates the composite state from the vacuum. Thus, the constituent counting scaling laws can be used to identify the twist of exotic hadronic candidates such as tetraquarks and pentaquarks. Effective field theories must consistently implement the scaling rules in order to be consistent with the fundamental theory. Here, we examine how one can apply constituent counting rules for the exclusive production of one or two neutral vector mesons V 0 in e + e ? annihilation, processes in which the V 0 can couple via intermediate photons. In the case of a (narrow) real V 0 , the photon virtuality is fixed to a precise value s 1 = m V 0 2 , thus treating the V 0 as a single fundamental particle. Each real V 0 thus contributes to the constituent counting rules with N V 0 = 1 . In effect, the leading operator underlying the V 0 has twist 1. Thus, in the specific physical case of single or double on-shell V 0 production via intermediate photons, the predicted scaling from counting rules coincides with vector-meson dominance (VMD), an effective theory that treats V 0 as an elementary field. However, the VMD prediction fails in the general case where the V 0 is not coupled through an elementary photon field, and then the leading-twist interpolating operator has twist N V 0 = 2 . Analogous effects appear in p p scattering processes.
机译：QCD成分计数规则根据参与硬子过程的初始状态和最终状态中基本成分的总数，定义了高动量传递时排他的强子散射和电磁散射幅度的缩放行为。缩放定律反映了每个强子的前导Fock状态的扭曲，因此反映了根据真空创建复合状态的前导算子。因此，成分计数缩放定律可用于识别诸如四夸克和五夸克等外来强子候选者的扭曲。有效的现场理论必须一致地执行缩放规则，以便与基本理论相一致。在这里，我们研究如何将成分计数规则应用于e + e中一个或两个中性矢量介子V 0的排他性生成？ 0灭，V 0可以通过中间光子耦合的过程。在（窄）实数V 0的情况下，光子虚拟度固定为精确值s 1 = m V 0 2，因此将V 0视为单个基本粒子。每个实数V 0因此有助于N V 0 = 1的组成计数规则。实际上，V 0下方的前导算子具有1的扭曲。因此，在通过中间光子产生单或双壳V 0的特定物理情况下，根据计数规则预测的缩放比例与矢量介子优势（VMD）相符，这是将V 0视为基本场的有效理论。然而，在V 0没有通过基本光子场耦合的一般情况下，VMD预测失败，然后超前插值内插算子的扭曲N V 0 = 2。在p p散射过程中会出现类似的影响。

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