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arXiv 2104.00329hep-lat
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核子电磁形状因子格点计算中的$Nπ$态污染

$Nπ$-state contamination in lattice calculations of the nucleon electromagnetic form factors

Oliver Bar, Haris Colic

摘要:

在手征微扰理论下,研究了核子-π介子态对与核子电磁形状因子格点计算有关的QCD两点和三点函数的贡献。对于首阶,结果仅依赖于几个实验上已知的低能常数,并且核子-π-态对形状因子的贡献可以估计。核子-π介子态对电形状因子$G_{\rm E}(Q^2)$的贡献在源-汇分离为2 fm的+5%水平,并且随着动量转移$Q^2$的增加而增加。对于磁形状因子,核子-π-态的贡献导致对$G_{\rm M}(Q^2)$的低估约5%,并随着$Q^2$的增加而减小。对于目前晶格模拟中可获得的较小的源-汇分离,影响较大,尽管ChPT结果可能不适用于这种小时间分离。尽管如此,与$t\approx 1.6$ fm上的点阵数据进行比较还是相当有效的。

英文摘要:

The nucleon-pion-state contribution to QCD two-point and three-point functions relevant for lattice calculations of the nucleon electromagnetic form factors are studied in chiral perturbation theory. To leading order the results depend on a few experimentally known low-energy constants only, and the nucleon-pion-state contribution to the form factors can be estimated. The nucleon-pion-state contribution to the electric form factor $G_{\rm E}(Q^2)$ is at the +5 percent level for a source-sink separation of 2 fm, and it increases with increasing momentum transfer $Q^2$. For the magnetic form factor the nucleon-pion-state contribution leads to an underestimation of $G_{\rm M}(Q^2)$ by about 5 percent that decreases with increasing $Q^2$. For smaller source-sink separations that are accessible in present-day lattice simulations the impact is larger, although the ChPT results may not be applicable for such small time separations. Still, a comparison with lattice data at $t\approx 1.6$ fm works reasonably well.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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