反冲几何揭示向前Z⁰产生中的胶子饱和
Recoil Geometry Unmasks Gluon Saturation in Forward $Z^0$ Production
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中文总结 AI 辅助
该研究利用基准反冲减除结合CGC与SCET方法，通过探测器几何调控反冲，在向前Z⁰产生中揭示了胶子饱和效应。
中文摘要 AI 辅助
胶子饱和会在原子核中产生特征性的横动量展宽，但量子色动力学（QCD）辐射会极大地掩盖这一信号。我们表明，基准反冲减除能将探测器接受度转化为横动量投影器，从而在向前Z⁰产生中揭示该展宽。从玻色子横动量中减去所选快度区间内测量到的强子反冲，可定义出剩余动量。在领头阶近似下，该区间内的辐射反冲会被抵消，而剩余动量仍对小x核场保持敏感性。结合小x靶的色玻璃凝聚（CGC）描述与有限快度覆盖的软共线有效理论（SCET）重求和，我们发现基准快度覆盖|η^lab|<2.5会将有效 hard 标度从M_Z≈91.2 GeV降低到 Sudakov 演化的约7.5 GeV。饱和尺度增大会展宽剩余动量分布并削弱反冲对齐，而更宽的覆盖范围会使两种可观测量中的质子-原子核分离更清晰。因此，探测器几何提供了对微扰反冲的可调控制，可用于探测非线性小x量子色动力学。
英文摘要
Gluon saturation produces characteristic transverse-momentum broadening in nuclei, but QCD radiation largely washes out this signature. We show that fiducial recoil subtraction turns detector acceptance into a transverse-momentum projector that unmasks the broadening in forward $Z^0$ production. Subtracting the hadronic recoil measured in a chosen rapidity interval from the boson transverse momentum defines a residual momentum. At leading power, the radiative recoil in this interval cancels, while the residual momentum retains sensitivity to the small-$x$ nuclear field. Combining a CGC description of the small-$x$ target with soft-collinear effective theory (SCET) resummation for finite rapidity coverage, we find that a benchmark rapidity coverage $|η^{\rm lab}|<2.5$ lowers the effective hard scale from $M_Z\simeq 91.2$ GeV to about $7.5~\mathrm{GeV}$ of the Sudakov evolution. Increasing the saturation scale broadens the residual-momentum distribution and weakens recoil alignment, whereas wider coverage makes the proton--nucleus separation clearer in both observables. Detector geometry thus provides tunable control over perturbative recoil, enabling a probe of nonlinear small-$x$ QCD.
发表机构
- Fudan University（复旦大学）
- Peking University（北京大学）
- Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）
- Shandong University (Qingdao)（山东大学（青岛））
机构由 AI 辅助整理，请以论文原文为准。
