标题： 低能区手征有效场论中电子-正电子湮灭为四个π介子的研究 显示英文标题

标题： Study of electron-positron annihilation into four pions within chiral effective field theory in the low energy region

摘要： 在本文中，我们采用手征有效场论研究低能区内的正电子湮没为四个π介子的过程，该低能区在$E_{c.m.}\leq 0.6$GeV 以下。 通过$SU(3)$手征微扰理论计算到次领头阶的截面预测，在能量区间 [0.6-0.65] GeV 内比实验数据小，尽管这些数据点较少且统计精度不高。 随后，我们应用共振手征理论来包含共振贡献，其中最轻的标量和矢量被写入有效拉格朗日量中。 研究了一系列相关的衰变宽度和矢量的质量以确定未知耦合。 共振贡献应比手征微扰理论的贡献大一个数量级，但仍比数据小一个到两个数量级。 这种显著差异促使新的实验测量提供更多的指导。 我们也计算了四个π介子通道对μ子反常磁矩$(g-2)_\mu$的强子真空极化贡献。 在 RChT 理论框架下，从阈值到 0.6 GeV 能量范围内的贡献分别为$a_\mu=(0.6678\pm0.0933)\times10^{-16}$和$a_\mu=(0.4575\pm0.0517)\times10^{-16}$，对应于过程$e^+e^-\to\pi^+\pi^+\pi^-\pi^-$和$\pi^0\pi^0\pi^+\pi^-$。 显示英文摘要

摘要： In this paper, we employ chiral effective field theory to study the process of electron-positron annihilation into four pions in the low energy region within $E_{c.m.}\leq 0.6$ GeV. The prediction of the cross-section is obtained through $SU(3)$ chiral perturbation theory up to the next-to-leading order, which is smaller than the experimental data in the energy region [0.6-0.65] GeV, though the data has only a few points and poor statistics. Then, the resonance chiral theory is applied to include the resonance contribution, with the lightest scalars and vectors written in the effective Lagrangians. A series of relevant decay widths and the masses of the vectors are studied to fix the unknown couplings. The resonance contribution should be one order larger than that of the chiral perturbation theory but still one to two orders smaller than the data. The significant discrepancy urged the new experimental measurements to give more guidance. We also compute the hadronic vacuum polarization contribution from the four pion channels to the anomalous magnetic moment of the muon, $(g-2)_\mu$. In the energy range from threshold up to 0.6 GeV within RChT, the contributions are $a_\mu=(0.6678\pm0.0933)\times10^{-16}$ and $a_\mu=(0.4575\pm0.0517)\times10^{-16}$ for the processes of $e^+e^-\to\pi^+\pi^+\pi^-\pi^-$, $\pi^0\pi^0\pi^+\pi^-$, respectively.