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arXiv 2610.20164hep-phhep-ex
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粲、底和顶夸克喷注在角空间与动量空间中的死锥效应

The dead-cone effect in charm, bottom and top quark jets in angular and momentum space

DRII-IPSA(IPSA学院);Sorbonne Université et CNRS(索邦大学与法国国家科学研究中心);Max-Planck-Institut für Physik(马克斯·普朗克物理研究所)

Redamy Perez-Ramos, Stefan Kluth, Wolfgang Ochs

AI总结:

本研究利用角分布和动量谱,结合LEP数据与蒙特卡罗模拟,揭示粲、底、顶夸克的死锥效应,确立动量谱为顶夸克死锥效应的定量观测指标,给出质量依赖型QCD辐射的统一描述。

摘要:

死锥效应反映了重夸克QCD辐射的质量依赖性,我们利用二维角分布和单粒子 inclusiv 动量谱,对从粲、底到顶夸克的这一现象展开研究。角分布体现了重夸克方向周围辐射的耗尽,而动量谱为该效应提供了定量可观测指标。对于粲和底夸克喷注,从Z极点处的LEP数据重构的碎裂函数呈现出高动量粒子的强压低,这一现象可通过微扰QCD的修正领头对数近似(Modified Leading Logarithmic Approximation)定量描述。我们将分析扩展到质心系能量√s=1 TeV的情况,采用蒙特卡罗模拟开展研究。假设存在稳定顶夸克样本,可分离出初级顶夸克的辐射模式;而物理衰变t→bW会引入来自tb色偶极的相干辐射,掩盖了初级死锥。通过利用对b夸克发射角Θ_b的依赖性,我们外推至Θ_b→0,重构出初级顶夸克部分子的动量谱。相比之下,小角度胶子和部分子分布因衰变b夸克的辐射,无法收敛到稳定顶夸克的死锥模式。这些发现确立了 inclusiv 动量谱作为顶夸克死锥效应的可靠定量可观测指标,并为从粲到顶夸克的质量依赖型QCD辐射提供了统一描述。

英文摘要:

The dead-cone effect reflects the mass dependence of QCD radiation from heavy quarks. We investigate this phenomenon from charm and bottom to top quarks using two-dimensional angular distributions and single-particle inclusive momentum spectra. The angular distributions illustrate the depletion of radiation around the heavy-quark direction, while the momentum spectra provide a quantitative observable of the effect. For charm and bottom jets, fragmentation functions reconstructed from LEP data at the $Z$ pole exhibit a strong suppression of high-momentum particles, quantitatively described within the Modified Leading Logarithmic Approximation of perturbative QCD. The analysis is extended to $\sqrt{s}=1$ TeV using Monte Carlo simulations. A hypothetical stable-top sample isolates the primary top-quark radiation pattern, whereas the physical decay $t\to bW$ introduces coherent radiation from the $tb$ colour dipole, obscuring the primary dead cone. By exploiting the dependence on the $b$-quark emission angle $Θ_b$, we reconstruct the primary top-quark parton momentum spectrum through extrapolation to $Θ_b\to0$. In contrast, the small-angle gluon and parton distributions do not converge to the stable-top dead-cone pattern because of radiation from the decay $b$ quark. These findings establish the inclusive momentum spectrum as a robust quantitative observable of the top-quark dead-cone effect and provide a unified description of mass-dependent QCD radiation from charm to top.

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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