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arXiv 1401.2852hep-ph
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Schwinger-Dyson形式中的夸克标量荷、轴荷和赝标荷

Quark scalar, axial, and pseudoscalar charges in the Schwinger-Dyson formalism

Nodoka Yamanaka, Shotaro Imai, Takahiro M. Doi, Hideo Suganuma

备注：
28 pages, 22 figures
发表信息：
Phys.Rev. D89 (2014) 074017
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摘要：

我们在朗道规范QCD的Schwinger-Dyson形式中计算了夸克的标量、轴向和赝标荷。结果发现，相对于裸夸克的贡献，价夸克的缀饰夸克标量密度显著增加，定性地解释了唯象已知的π-核子σ项的值和格点量子色动力学给出的值.此外，我们表明，理查森的夸克间的潜力抑制夸克标量密度在东岛-米兰斯基近似。这一事实表明，夸克标量密度是一个对夸克禁闭敏感的可观测量。对于夸克的轴荷，我们发现它是由于胶子动力学抑制。猝灭分析的结果与等矢量轴向耦合常数$g_A$的实验数据定性一致。我们表明，淬火轴向电荷的抑制是由于类似的夸克张量电荷的机制。在Schwinger-Dyson方程中，由于反常效应，夸克轴向荷被抑制得更厉害。夸克赝标密度被发现是大的，并且是发散的裸夸克变得无质量。这一结果与唯象流代数分析相一致，并很好地解释了π-极贡献的优势。

英文摘要：

We calculate the scalar, axial, and pseudoscalar charges of the quark in the Schwinger-Dyson formalism of Landau gauge QCD. It is found that the dressed quark scalar density of the valence quark is significantly enhanced against the bare quark contribution, and the result explains qualitatively the phenomenologically known value of the pion-nucleon sigma term and also that given by lattice QCD. Moreover, we show that the Richardson's interquark potential suppresses the quark scalar density in the Higashjima-Miransky approximation. This fact suggests that the quark scalar density is an observable that is sensitive to quark confinement. For the quark axial charge, we find that it is suppressed due to the gluon dynamics. The result of the quenched analysis agrees qualitatively with the experimental data of the isovector axial coupling constant $g_A$. We show that the suppression of the quenched axial charge is due to a mechanism similar to that of the quark tensor charge. In the Schwinger-Dyson equation with the leading unquenching quark-loop contribution the quark axial charge is more suppressed, due to the anomaly effect. The quark pseudoscalar density is found to be large, and is divergent as the bare quark becomes massless. This result is in agreement with the phenomenological current algebraic analysis, and explains well the dominance of the pion-pole contribution.

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