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arXiv 2106.01437hep-ph
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双光子反应中的轴矢量贡献:QCD中NNLO的π跃迁形状因子和深虚康普顿散射

The axial-vector contributions in two-photon reactions: pion transition form factor and deeply-virtual Compton scattering at NNLO in QCD

V. M. Braun, A. N. Manashov, S. Moch, J. Schoenleber

摘要:

利用基于共形对称的方法计算了$\overline{\rm MS}$方案中轴矢量对双光子过程贡献的双圈系数函数。这是微扰QCD中π介子跃迁形状因子$γ^\astγ\to π$的完整次-次-首阶(NNLO)计算的最后一个缺失元素。相应的高统计量测量计划由Belle II合作,并将允许一个强有力的约束的π介子光锥分布振幅。计算的NNLO修正证明是相当大的,必须加以考虑。相同的系数函数决定了轴向矢量广义部分子分布对深度虚康普顿散射的贡献,该散射在JLAB 12 GeV加速器上进行了研究,由CERN的COMPASS进行了研究,并且将来将在电子离子对撞机EIC进行研究。

英文摘要:

Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the axial-vector contributions to two-photon processes in the $\overline{\rm MS}$ scheme. This is the last missing element for the complete next-to-next-to-leading order (NNLO) calculation of the the pion transition form factor $γ^\astγ\to π$ in perturbative QCD. The corresponding high-statistics measurement is planned by the Belle II collaboration and will allow one to put strong constraints on the pion light-cone distribution amplitude. The calculated NNLO corrections prove to be rather large and have to be taken into account. The same coefficient function determines the contribution of the axial-vector generalized parton distributions to deeply-virtual Compton scattering which is investigated at the JLAB 12 GeV accelerator, by COMPASS at CERN, and in the future will be studied at the Electron Ion Collider EIC.

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