发表机构
Indian Institute of Technology Delhi（德里印度理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究从 HERA 实验的排他性 J/ψ产生提取小 x 处质子胶子结构，通过解析计算和拟合模型，精确确定质子胶子云形状，其热点有特定核心与晕结构，且形状与相关参数无关，拟合有稳定能量依赖性。
AI 中文摘要
我们展示了从 HERA 的 H1 和 ZEUS 实验中通过排他性 J/ψ产生提取的小 x 处质子胶子结构的全面研究结果。我们给出了在质子热点模型中领先扭转下相干和非相干截面的解析计算。将模型与所有可用的排他性衍射光产生测量数据拟合，提取出质子胶子云的精确形状。模型与数据拟合良好，χ²/ndf = 0.77。发现热点有一个大小为 0.105(1) fm 的微扰高斯核心，被一个 0.220(2) fm 的非微扰指数晕包围。该形状与\xpom 或热点数量无关。拟合还显示出有效α' = 0.046(19)时显著稳定的能量依赖性。
英文摘要
The transverse shape of the proton's small-$x$ gluon distribution is determined from exclusive $J/ψ$ photoproduction at HERA. We derive analytic expressions for the coherent and incoherent diffractive cross sections in the hotspot model at leading twist, enabling a global fit to all 104 available H1 and ZEUS data points, with $|t|<30~{\rm GeV}^2$ and $40\leq W\leq 251~{\rm GeV}$, with $χ^2/{\rm ndf}=0.72$. The gluonic hotspots are resolved into a core of size 0.088(10) fm surrounded by an exponential halo of range 0.20(2) fm, matching the penetration depth of lattice flux tubes. This shape is stable over $\xpom$ and over the assumed number of hotspots in the range $5\leq N_{hs}\leq 12$. We find the Ginzburg-Landau parameter of the QCD vacuum to be $κ=2.7(7)$, which corresponds to fluxtube geometry in a type-II dual superconductor. The calculated QCD string-tension from the extracted parameter values is in agreement with theoretical calculations on the lattice. The gluonic geometry evolves only through a slow transverse diffusion of the hotspot centers with $α'_{\rm eff.}=0.060(19)~{\rm GeV}^{-2}$, while the incoherent cross section at small $|t|$ is dominated by shot-noise fluctuations at the order of a few gluons per hotspot.
Comments14 pages, 6 figures
