论文标题
LCSR中的Pion-Photon转变形式和渐近学测试
Pion-photon transition form factor in LCSR and tests of asymptotics
论文作者
论文摘要
我们使用固定顺序QCD扰动理论中的最先进的实现光锥总规则（LCSR）来研究Pion-Photon过渡形式（TFF）$ f^{γ*γπ^0}（q^2）$。分散关系中的光谱密度包括直到近隔至领先阶（NNLO）的所有已知辐射校正，以及所有扭曲贡献，直到六个订单。 TFF的预测是扭曲二的各种Pion分布幅度（DAS）的预测，其中包括两环进化，这些演化是夸克质量阈值的。为了与数据进行更现实的比较，量化了主要理论不确定性的影响。与NLO和NNLO的准确性相比，根据保形系数$ A_2 $和$2σ$误差区域，分析了各种PION DAS的特性。我们的结果为临时DA的变化提供了更严格的界限，并阐明了计算出的TFF的相应渐近行为。
We study the pion-photon transition form factor (TFF) $F^{γ*γπ^0}(Q^2)$ using a state-of-the art implementation of light cone sum rules (LCSRs) within fixed-order QCD perturbation theory. The spectral density in the dispersion relation includes all currently known radiative corrections up to the next-to-next-to-leading-order (NNLO) and all twist contributions up to order six. Predictions for the TFF are obtained for various pion distribution amplitudes (DAs) of twist two, including two-loop evolution which accounts for heavy-quark mass thresholds. The influence of the main theoretical uncertainties is quantified in order to enable a more realistic comparison with the data. The characteristics of various pion DAs are analyzed in terms of the conformal coefficients $a_2$ and $a_4$ in comparison with the $1σ$ and $2σ$ error regions of the data and the most recent lattice constraints on $a_2$ with NLO and NNLO accuracy. Our results provide more stringent bounds on the variation of the pion DA and illuminate the corresponding asymptotic behavior of the calculated TFF.
