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arXiv 1303.4983hep-ph
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核子-共振相互作用的规范不变顶点和点不变顶点

Gauge- and point-invariant vertices of nucleon-to-resonance interactions

G. Vereshkov, N. Volchanskiy

摘要:

我们构造了核子N与高自旋共振态R的相互作用在拉里塔-施温格场的点变换和规范变换下的不变性。它被发现为任意高自旋的共振点和规范不变性的要求,唯一地确定了一个拉格朗日的NR相互作用与π介子,光子和矢量介子,这可能会减少模型的模糊性,在涉及这些顶点的有效场计算。考虑到NR与光子和矢量介子的相互作用,对称性提供了三个NR顶点的分类。在矢量介子占优模型中考虑了点不变和规范不变形状因子的Q^2依赖性。该模型与实验数据吻合较好。此外,我们还指出了形状因子的Q^2依赖性的一些经验模式:N-Delta(1232)形状因子比的低Q^2标度以及N-N(1520)和N-N(1680)跃迁的形状因子之间的关系。

英文摘要:

We construct interactions of nucleons N with higher-spin resonances R invariant under point and gauge transformations of the Rarita-Schwinger field. It is found for arbitrarily high spin of a resonance that the requirement of point- and gauge-invariance uniquely determines a Lagrangian of NR interactions with pions, photons, and vector mesons, which might reduce model ambiguity in effective-field calculations involving such vertices. Considering the NR interactions with photons and vector mesons, the symmetry provides a classification of three NR vertices in terms of their differential order. The Q^2 dependencies of the point and gauge invariant form factors are considered in a vector-meson-dominance model. The model is in good agreement with experimental data. In addition, we point out some empirical patterns in the Q^2 dependencies of the form factors: low-Q^2 scaling of the N-Delta(1232) form factor ratios and relations between form factors for N-N(1520) and N-N(1680) transitions.

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