Institut für Theoretische Teilchenphysik und Kosmologie, RWTH Aachen University, D-52056 Aachen, Germany.
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
Phys Rev Lett. 2016 Feb 26;116(8):082003. doi: 10.1103/PhysRevLett.116.082003. Epub 2016 Feb 25.
We present the first complete next-to-next-to-leading order (NNLO) QCD predictions for differential distributions in the top-quark pair production process at the LHC. Our results are derived from a fully differential partonic Monte Carlo calculation with stable top quarks which involves no approximations beyond the fixed-order truncation of the perturbation series. The NNLO corrections improve the agreement between existing LHC measurements [V. Khachatryan et al. (CMS Collaboration), Eur. Phys. J. C 75, 542 (2015)] and standard model predictions for the top-quark transverse momentum distribution, thus helping alleviate one long-standing discrepancy. The shape of the top-quark pair invariant mass distribution turns out to be stable with respect to radiative corrections beyond NLO which increases the value of this observable as a place to search for physics beyond the standard model. The results presented here provide essential input for parton distribution function fits, implementation of higher-order effects in Monte Carlo generators, as well as top-quark mass and strong coupling determination.
我们给出了在 LHC 上进行顶夸克对产生过程的微分分布的首个完整次领头阶次（NNLO）QCD 预测。我们的结果来自于一个完全微分的部分子蒙特卡罗计算，其中包含稳定的顶夸克，并且不涉及除微扰级数的固定阶截断之外的任何近似。NNLO 修正改善了现有 LHC 测量[V. Khachatryan 等人（CMS 合作），Eur. Phys. J. C 75, 542 (2015)]与标准模型对顶夸克横向动量分布的预测之间的一致性，从而有助于缓解一个长期存在的差异。顶夸克对不变质量分布的形状对于 NLO 以上的辐射修正来说是稳定的，这增加了这个可观测量作为寻找超出标准模型物理的一个地方的价值。这里呈现的结果为部分子分布函数拟合、蒙特卡罗生成器中高阶效应的实现以及顶夸克质量和强耦合常数的确定提供了必要的输入。
