AI 中文总结
研究超外围铅铅碰撞中\(γγ\to ττ\)过程，通过对轻子横向动量分布似然拟合，约束\(τ\)轻子反常磁矩\(a_\tau\)并提取截面，给出\(a_\tau\)区间及高精度基准截面，与理论预测一致。
AI 中文摘要
本文研究了在质心能量为5.02 TeV的超外围铅铅碰撞中，通过光子-光子融合产生\(τ\)轻子对（\(\gamma\gamma \to \tau \tau\)）的过程。数据集由CMS实验在2018年收集，对应积分亮度为1.70 nb\(^{-1}\)。分析了四种不同的\(\tau^+\tau^-\)衰变末态。通过对测量的轻子横向动量（\(p_\mathrm{T}\)）分布进行同时似然拟合，结合谱形状和归一化信息，来约束\(τ\)轻子的反常磁矩\(a_\tau\)并提取该过程的截面。测量得到\(a_\tau\)的95% CL区间为\(-0.039 \lt a_\tau \lt 0.032\)。对于\(p_\mathrm{T}^\tau \gt 1\) GeV且\(\lvert\eta^\tau\rvert \lt 3\)的\(τ\)轻子，基准截面\(\sigma_{\gamma\gamma \to \tau \tau}^\text{fid}\) = 555\(^{+60}_{-14}\) \(\mu\)b，这是LHC迄今为止对该过程最精确的测量，且与次领头阶量子电动力学预测一致。
英文摘要
The production of $τ$ lepton pairs via photon-photon fusion, $γγ\to ττ$, is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The dataset, collected by the CMS experiment in 2018, corresponds to an integrated luminosity of 1.70 nb$^{-1}$. Four different $τ^+τ^-$ decay final states are analyzed. A simultaneous likelihood fit to the measured lepton transverse momentum ($p_\mathrm{T}$) distributions, which incorporates information from both spectral shape and normalization, is used to constrain the anomalous magnetic moment of the $τ$ lepton, $a_τ$, and to extract the cross section of the process. The measured 95% CL interval for $a_τ$ is $-$0.039 $\lt$ $a_τ$ $\lt$ 0.032. The fiducial cross section, $σ_{γγ\to ττ}^\text{fid}$ = 555$^{+60}_{-14}$ $μ$b for tau leptons with $p_\mathrm{T}^τ$ $\gt$ 1 GeV and pseudorapidity $\lvertη^τ\rvert$ $\lt$ 3, is the most precise measurement for this process at the LHC to date and is in agreement with next-to-leading-order quantum electrodynamics predictions.
CommentsThis version has an updated author list. Submitted to Physics Letters B. All figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-24-011 (CMS Public Pages)
