We study the electroweak properties of pseudo-scalar mesons in the light and heavy-light sectors. In particular, we address the electromagnetic form factors and decay constants of the pion, kaon and D mesons. The structure of composite systems are given by the Bethe-Salpeter (BS) amplitude of a meson formed by a confined pair of constituent quark and antiquark, which in our work is written in terms of Pauli-Villars regulators. The analytical structure contains single poles in the complex momentum space. The BS amplitude takes into account poles due to the regulator parameters, while the quark-antiquark cut is avoided, implying in confined quarks with the property that the sum of the constituents masses can be larger than the mass of the meson. The one-loop expressions of the electroweak transition amplitudes are conveniently written in terms of light-front momentum. Technically, we introduce a Wick-rotation of he minus component of the momentum (k-minus) in the one-loop amplitudes allowing to avoid the cuts in the complex plane of this momentum variable without crossing them. This is particularly useful as we can study the electroweak properties with several models of the BS amplitude with different powers of Pauli-Villars regulators. The possibility to change the power of the BS amplitude is interesting in order to test the asymptotic behavior of the electromagnetic form factors searching for a suitable form that incorporates the expected QCD decaying power-law form. The results are compared with others models in the literature and with the experimental data.
Analysis of virtual meson production in solvable (1+1) dimensional scalar field theory
利用推广的Wick-Cutkosky模型的可解标量场理论，研究了（1+1）维虚标量介子产生过程中的光阵面时间有序振幅.在（1+1）维虚介子产生过程的计算中只有一个康普顿形状因子（CFF），我们计算了$Q^2>0$和$t<0$整个运动学区域的CFF的实部和虚部.然后，我们分析了每个光阵面的时间顺序振幅的CFF的$Q^2$和$t$的函数的贡献。特别是，我们讨论的意义的“猫的耳朵”的贡献规范不变性和有效性的“手提包优势”的制定中的广义部分子分布（GPD）的功能通常用于分析的深度虚拟介子生产过程。我们明确地从$-t/Q^2<<1$极限中的“手提包”光阵面时间顺序振幅导出GPD，并验证了DGSTAR和ERBL区域的GPD在光阵面纵向动量分数上的积分对应于我们最近报道的电磁形状因子的价和非价贡献[Phys. Rev. D $\textbf{103}$，076002（2021）]。我们还讨论了GPD与部分子分布函数之间的对应关系，以及新的光锋纵向空间变量$\tilde{z}$在分析轻子-强子深部非弹性散射过程中的应用。
