AI 中文总结
研究大型强子对撞机中顶 - 反顶夸克对在接近阈值时的产生，给出三种 NLO + PS 类型发生器，用于探讨增强非相对论效应大小、其归因于粲夸克偶素产生的贡献及顶夸克有限宽度对阈值增强修正的影响。
AI 中文摘要
在这项工作中，我们考虑大型强子对撞机中顶 - 反顶夸克对产生的情况，此时该对的质量相对接近标称阈值，即两倍顶夸克极点质量。在这种情况下，会出现可在微扰理论中计算到所有阶次的增强微扰修正。我们给出了三种 NLO + PS 类型（可与部分子喷注相连接的次领头阶）的发生器，它们包含这些阈值增强效应。利用这些发生器，我们研究了以下问题：在已知的 NLO 和 NNLO 微扰结果中不存在的增强非相对论效应的大小；这些效应中可大致归因于粲夸克偶素产生的贡献大小；以及顶夸克的有限宽度在多大程度上影响阈值增强修正。我们的发生器与 ATLAS 和 CMS 合作组最近在赝标量通道中观察到的阈值附近增强的 $t{\bar t}$ 产生相关。
英文摘要
In this work we consider the production of a top-antitop pair at the LHC when the mass of the pair is relatively near to the nominal threshold, that is to say to twice the top pole mass. In this regime, enhanced perturbative corrections arise that can be computed to all orders in perturbation theory. We present three generators of the NLO+PS kind (Next-to-Leading-Order that can be interfaced to parton showers) that include these threshold enhanced effects. Using these generators we address the following questions: what is the size of enhanced non-relativistic effects that are not already present in the well known NLO and NNLO perturbative results; what is the size of the contribution from these effects that can be loosely attributed to toponium production; and to what extent the finite width of the top quark affects threshold enhanced corrections. Our generators are relevant for the recent observation of enhanced $t{\bar t}$ production near threshold in the pseudoscalar channel by the ATLAS and CMS collaborations.
Comments38 pages, 8 figures, 8 tables; In this replacement: minor adjustments to figures and added important reference with appropriate comments
