Form factors for \(\eta _c\) and \(\chi _{c0}\) have been simulated based on \(N_f=2\) Twisted Mass Lattice Quantum Chromodynamics (Lattice QCD) gauge configurations. We construct particle interpolation operators by variational method that can significantly improve signal-to-noise ratio of correlation functions. We apply twisted boundary conditions to compute corresponding correlation functions which make us obtain form factors with more small four-momentum transfer. Furthermore, we fit charge radius for \(\eta _c\) and \(\chi _{c0}\), respectively. The results obtained in this simulation could be considered as a ground test to calculate branch ratio decay width of \(\chi _{c0,1,2}\rightarrow {\gamma {J/\psi }}\) on lattice in future.

\（\ eta _c \）和\（\ chi _ {c0} \）的形状因数已根据\（N_f = 2 \）扭曲质量格子量子色动力学（Lattice QCD）量规配置进行了模拟。我们通过变分方法构造粒子插值算子，可以显着提高相关函数的信噪比。我们应用扭曲边界条件来计算相应的相关函数，从而使我们获得具有较小四动量传递的形状因子。此外，我们分别拟合\（\ eta _c \）和\（\ chi _ {c0} \）的电荷半径。在此模拟中获得的结果可以视为计算分支比衰减宽度的基础测试。\（\ chi _ {c0,1,2} \ rightarrow {\ gamma {J / \ psi}} \\）将来在晶格上。