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arXiv 2409.20544hep-phhep-exnucl-exnucl-th
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具有完整GPD演化的遍举 $J/\psi$ 与 $\Upsilon$ 光生过程的完整单圈研究

Complete 1-loop study of exclusive $ J/ψ$ and $ Υ$ photoproduction with full GPD evolution

Chris Flett, Jean-Philippe Lansberg, Saad Nabeebaccus, Maxim Nefedov, Pawel Sznajder, Jakub Wagner

备注：
7 pages, 3 figures, Presented by S. Nabeebaccus at the 31st International Workshop on Deep Inelastic Scattering (DIS2024)
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AI总结：

本文首次在单圈水平上结合完整领头对数GPD演化计算 $J/\psi$ 和 $\Upsilon$ 的遍举光生，并通过高能因子化与双对数近似匹配重求和解决因子化标度不稳定问题，结果与H1和ZEUS数据一致。

摘要：

我们讨论重矢量夸克偶素（即 $J/\psi$ 和 $\Upsilon$）在 $\alpha_s$ 单圈水平上的遍举光生过程。在共线因子化（CF）框架下，该过程的振幅通过硬部分子子振幅与普适广义部分子分布（GPD）的卷积得到。我们首次完成了包含完整领头对数（LL）GPD演化的单圈完整计算。我们首先证明了当因子化标度 $\mu_F$ 变化时，高能下截面存在巨大的不稳定性。这种不稳定性此前已在文献中被报道过，其产生原因是过程硬标度（此处为重夸克偶素的质量）与过程质心能量之间的巨大差异所产生的大对数。这一问题在单举重矢量夸克偶素光生过程中也有报道。我们证明，可以通过使用高能因子化（HEF）对这些大对数进行重求和来解决该问题，具体做法是利用双对数近似（DLA）与CF结果进行匹配，从而与GPD的固定阶演化保持一致。最后，我们证明由这种匹配得到的截面除了不受前述因子化标度变化不稳定性的影响外，还与 $J/\psi$ 产生的H1数据以及 $\Upsilon$ 产生的ZEUS数据相一致。

英文摘要：

We discuss the exclusive photoproduction of a heavy vector quarkonium, namely $J/ψ$ and $Υ$ at 1-loop in $α_s$. In collinear factorisation (CF), the amplitude for such a process is obtained by the convolution of a hard partonic sub-amplitude, with a universal generalised parton distribution (GPD). For the first time, we perform a complete calculation at 1-loop including full leading-log (LL) GPD evolution. We first demonstrate the huge instability of the cross section at high energies when the factorisation scale $μ_F$ is varied. This instability has been reported previously in the literature, and occurs due to the large logarithms generated by the huge difference between the hard scale of the process, which is the mass of the heavy quarkonium here, and the centre-of-mass energy of the process. This problem was also reported in inclusive heavy vector quarkonium photoproduction. We show that this issue can be resolved by resumming these large logarithms using high-energy factorisation (HEF), by performing a matching with the result in CF using the doubly logarithmic approximation (DLA) in order to be consistent with the fixed order evolution of GPDs. Finally, we show that the cross sections obtained from such a matching, besides being free from the previously mentioned factorisation scale variation instabilities, are consistent with the H1 data for $J/ψ$ production and with the ZEUS data for $Υ$ production.

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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