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arXiv 2501.09699hep-ph
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全息QCD中的张量介子跃迁形状因子与μ子g-2

Tensor meson transition form factors in holographic QCD and the muon $g-2$

Luigi Cappiello, Josef Leutgeb, Jonas Mager, Anton Rebhan

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REVTEX, 39 pages, 3 figures, 3 tables. v4: references added, (4.13) corrected, minor improvements (results unchanged)
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AI总结：

本文在全息QCD硬壁模型中首次完整评估了张量介子对μ子反常磁矩HLbL散射的贡献，发现其结果为正且量级达10^-11，可能解释色散与晶格结果间的差异。

摘要：

尽管张量介子在光子-光子碰撞中占据重要地位，但直到最近，它们对μ子反常磁矩的强子光生光散射（HLbL）部分的贡献估计仍仅在几个10^-12的水平。近期在色散方法内的一项重新分析发现，在解决了以往方法中运动学奇点的问题后，若采用简单的夸克模型计算跃迁形状因子，会得到更大的结果（几个10^-11），且符号与以往结果相反。本文中，我们给出了在全息QCD硬壁模型内对张量介子贡献的首次完整评估，该模型惊人地再现了主导的f_2(1270)的质量、双光子宽度以及观测到的单虚跃迁形状因子。由于存在夸克模型和最低阶共振手征理论中所没有的第二结构函数，a_μ的结果变为正而非负，且量级同样为几个10^-11。我们发现，张量介子的无限塔允许填补由轴矢量介子贡献留下的HLbL振幅对称纵向短程约束的空白。匹配相应的领先阶OPE结果，得到的双光子耦合与观测到的基态f_2、a_2、f_2'多重态的综合效应一致，总a_μ^Tensor贡献为+12.4×10^-11；采用F_ρ拟合后，该值略微降至+11.1×10^-11。来自张量部分的这种量级的贡献可能解释了最新色散与晶格计算a_μ^HLbL结果之间的差异。

英文摘要：

Despite the prominence of tensor mesons in photon-photon collisions, until recently their contribution to the hadronic light-by-light (HLbL) scattering part of the anomalous magnetic moment of the muon has been estimated to be at the level of only a few $10^{-12}$. A recent reanalysis within the dispersive approach has found that after resolving the issue of kinematic singularities in previous approaches, a larger result is obtained, a few $10^{-11}$, and with opposite sign as in previous results, when a simple quark model for the transition form factors is employed. In this paper, we present the first complete evaluation of tensor meson contributions within a hard-wall model in holographic QCD, which reproduces surprisingly well mass, two-photon width, and the observed singly virtual transition form factors of the dominant $f_2(1270)$. Due to a second structure function that is absent in the quark model and in lowest-order resonance chiral theory, the result for $a_μ$ turns out to be positive instead of negative, and also with a magnitude of a few $10^{-11}$. We find that the infinite tower of tensor mesons permits to fill the gap in the symmetric longitudinal short-distance constraint on the HLbL amplitude left by the contribution of axial vector mesons. Matching the corresponding leading-order OPE result leads to two-photon couplings consistent with the observed combined effects of the ground-state $f_2,a_2,f_2'$ multiplet and a total $a_μ^\mathrm{Tensor}$ contribution of $+12.4\times 10^{-11}$; with an $F_ρ$ fit this is reduced slightly to $+11.1\times 10^{-11}$. A contribution of this size from the tensor sector could explain the tension between the most recent dispersive and lattice results for $a_μ^\mathrm{HLbL}$.

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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