A Combined Study of the Pion’s Static Properties and form Factors
A Combined Study of the Pion’s Static Properties and form Factors
复制标题
DOI：
10.1007/s00601-013-0682-5
复制
发表时间：
2013-03
期刊：
影响因子：
1.6
通讯作者：
B. El-Bennich;J. de Melo;T. Frederico
中科院分区：
文献类型：
--
作者：
B. El-Bennich;J. de Melo;T. Frederico
我们在一个光阵面模型中，一致地研究了π介子的静态观测值以及弹性和γ*γ→π 0跃迁的形状因子。一致性要求所有的计算都是在一个给定的模型中进行的，该模型具有相同的和单一的调整后的相关π介子束缚态波函数的长度或质量尺度参数。我们的结果与所有范围的数据都吻合得很好，包括最近贝儿关于γ*γ→π 0形状因子的数据，但BaBar关于这个转变形状因子的数据拒绝进行合理的比较。我们放松了束缚态波函数的初始约束，并显示BaBar数据可以部分地被容纳。然而，这是以与实验不一致的硬弹性形状因子为代价的。此外，π电荷半径比实验测定值小约40%.有人认为，减少电荷半径产生一个更硬的形状因子与束缚态振幅难以调和与软QCD。我们还讨论了为什么矢量主导型模型的光子夸克顶点，解析性和交叉对称的基础上，不太可能重现诉讼过渡形状因子的数据。
We study consistently the pion’s static observables and the elastic andγ*γ→π0transition form factors within a light-front model. Consistency requires that all calculations are performed within a given model with the same and single adjusted length or mass-scale parameter of the associated pion bound-state wave function. Our results agree well with all extent data including recent Belle data on theγ*γ→π0form factor at largeq2, yet the BaBar data on this transition form factor resists a sensible comparison. We relax the initial constraint on the bound-state wave function and show the BaBar data can partially be accommodated. This, however, comes at the cost of a hard elastic form factor not in agreement with experiment. Moreover, the pion charge radius is about 40 % smaller than its experimentally determined value. It is argued that a decreasing charge radius produces an ever harder form factor with a bound-state amplitude difficultly reconcilable with soft QCD. We also discuss why vector dominance type models for the photon-quark vertex, based on analyticity and crossing symmetry, are unlikely to reproduce the litigious transition form factor data.