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arXiv 2103.09131hep-ph
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π介子的重子含量

Baryonic content of the pion

Pablo Sanchez-Puertas, Enrique Ruiz Arriola, Wojciech Broniowski

备注：
7 pages, 5 figures; references and figures added; extended discussions; version accepted for publication in PLB
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摘要：

带电π介子的重子形状因子的产生是因为同位旋对称性被不相等的上下夸克质量$m_d>m_u$以及电磁效应破坏。我们从两个唯象的方法获得这个基本属性的估计：从简单的组分夸克模型，以及从拟合的$e^+e^- \to π^+ π^-$数据。我们所有的方法都得出这样的结果，即从形状因子的斜率中提取的重子均方半径对于$π^+$是正的，因此，外部区域有一个净重子，内部区域有一个净反重子密度，两者相互补偿，使得重子总数为零。对于$π^-$，效应大小相等，方向相反。我们估计相应的重子均方半径为$\langle r^2 \rangle_B^{π^{+}} = (0.03-0.04~{\rm fm})^2$。

英文摘要：

The baryon form factor of charged pions arises since isospin symmetry is broken with unequal up and down quark masses, $m_d>m_u$, as well as electromagnetic effects. We obtain estimates for this basic property in two phenomenological ways: from simple constituent quark models, as well as from fitting the $e^+e^- \to π^+ π^-$ data. All our methods yield the result that the baryon mean square radius, extracted from the slope of the form factor, is positive for $π^+$, hence a picture where the outer region has a net baryon, and the inner region a net antibaryon density, both compensating each other such that the total baryon number is zero. For $π^-$ the effect is equal and opposite. We estimate the corresponding mean squared baryon radius as $\langle r^2 \rangle_B^{π^{+}} = (0.03-0.04~{\rm fm})^2$.

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