格点量子色动力学中的$π^0$到双光子衰变
$π^0$ to two-photon decay in lattice QCD
摘要：
我们计算了格点量子色动力学中中性π介子（$π^0$）到离壳双光子（$γ^*γ^*$）跃迁的形状因子。跃迁形状因子可以从形式为（轴向-矢量）-（矢量）-（矢量）的三点函数中提取，作为离壳双光子动量的函数。由于轴反常在$π^0\toγγ$衰变过程中起着重要的作用，我们采用了重叠费米子，它保持了晶格上精确的手征对称性。利用基于矢量介子占优（VMD）模型的拟合函数外推到手征和消失光子动量极限后，我们发现Adler-Bell-Jackiw反常被正确地再现。
英文摘要：
We calculate the neutral pion ($π^0$) to off-shell two photon ($γ^*γ^*$) transition form factor in lattice QCD. The transition form factor can be extracted from the three-point function of the form (axial-vector)-(vector)-(vector) as a function of off-shell two-photon momentum. Since the axial-anomaly plays an important role in the $π^0\toγγ$ decay process, we employ the overlap fermion, which preserves the exact chiral symmetery on the lattice. After extrapolating to the chiral and the vanishing photon momentum limit with a fit function based on vector meson dominance (VMD) model, we find that the Adler-Bell-Jackiw anomaly is correctly reproduced.
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