光子-光子碰撞中μ子对和τ子对产生的量子电动力学次领头阶计算
Dimuon and ditau production in photon-photon collisions at next-to-leading order in QED
AI总结：
该研究在等效光子近似下计算了光子-光子碰撞中μ子对和τ子对产生的QED次领头阶修正，发现其能修改截面、分布尾部及高质量产额，改善LHC数据与理论一致性，为τ轻子反常磁矩等精确量提取提供关键支撑。
摘要：
在等效光子近似下，计算了光子-光子碰撞中μ子对和τ子对产生过程（γγ→μ⁺μ⁻、τ⁺τ⁻）的量子电动力学（QED）次领头阶（NLO）修正。我们主要考虑大型强子对撞机（LHC）上强子超外围碰撞中的γγ过程，但也讨论了大型电子正电子对撞机（LEP）上e⁺e⁻碰撞中的γγ→τ⁺τ⁻过程。研究发现，NLO项会将总 fiducial截面修改高达5%，增加双轻子非共面性和横向动量分布的尾部，并相对于包含碰撞光子极小虚部的领头阶预言，将高质量区域的产额降低高达15%。在LHC上，使用包含NLO QED修正的质子和铅离子电荷形状因子进行的计算，改善了所有测量微分分布的数据与理论一致性，并证明其是光子-光子过程中精确量（如τ轻子的反常磁矩）提取不可或缺的要素。
英文摘要：
Next-to-leading-order (NLO) quantum electrodynamics (QED) corrections to the production of muon and tau pairs in photon-photon collisions, $γγ\toμ^{+}μ^{-},τ^{+}τ^{-}$, are calculated in the equivalent photon approximation. We mostly consider $γγ$ processes in ultraperipheral collisions of hadrons at the LHC, but the $γγ\toτ^{+}τ^{-}$ process in $\mathrm{e}^+\mathrm{e}^-$ collisions at LEP is also discussed. The NLO terms are found to modify the total fiducial cross sections by up to 5%, increasing the tails of the dilepton acoplanarity and transverse momentum distributions, and depleting by up to 15% the yields at high masses, with respect to the leading-order predictions including the very small virtuality of the colliding photons. At the LHC, the calculations obtained with the charge form factor for protons and lead ions including the NLO QED corrections improve the data--theory agreement for all measured differential distributions, and prove an indispensable ingredient for the extraction of precision quantities in photon-photon processes, such as the anomalous magnetic moment of the tau lepton.
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