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arXiv 1802.02095hep-ph
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LHC的双光子产生:QCD研究直到NNLO

Diphoton production at the LHC: a QCD study up to NNLO

Stefano Catani, Leandro Cieri, Daniel de Florian, Giancarlo Ferrera, Massimiliano Grazzini

摘要:

我们考虑在大型强子对撞机的双光子对的生产,我们报告的QCD辐射校正的研究,下一个到下一个到领先的顺序(NNLO)。我们提出了一个详细的比较下一个领先的顺序(NLO)的标准和光滑的圆锥隔离标准内获得的结果,通过研究对隔离参数的依赖。我们强调的两个隔离标准内的不同部分子过程的作用,我们表明,它们产生大的辐射修正这两个标准。光滑锥隔离是计算QCD辐射修正的一种一致的方法。如果光子隔离是足够紧密的,我们表明,两个隔离程序的非线性光学结果是相互一致的微扰的不确定性。然后,我们将我们的研究扩展到NNLO使用光滑锥隔离。我们讨论的NNLO修正和相应的扰动不确定性的基准截面和分布的影响,我们评论与一些大型强子对撞机数据的比较。在我们的整个研究中,我们注意到了应用于光子的运动学选择切割所产生的主要特征。特别是,我们研究软胶子奇点出现在微扰计算的不变质量分布的光子对,光子的横动量谱,和基准截面与非对称和对称的光子横动量削减,我们提出了他们的行为在解析形式。

英文摘要:

We consider the production of prompt-photon pairs at the LHC and we report on a study of QCD radiative corrections up to the next-to-next-to-leading order (NNLO). We present a detailed comparison of next-to-leading order (NLO) results obtained within the standard and smooth cone isolation criteria, by studying the dependence on the isolation parameters. We highlight the role of different partonic subprocesses within the two isolation criteria, and we show that they produce large radiative corrections for both criteria. Smooth cone isolation is a consistent procedure to compute QCD radiative corrections at NLO and beyond. If photon isolation is sufficiently tight, we show that the NLO results for the two isolation procedures are consistent with each other within their perturbative uncertainties. We then extend our study to NNLO by using smooth cone isolation. We discuss the impact of the NNLO corrections and the corresponding perturbative uncertainties for both fiducial cross sections and distributions, and we comment on the comparison with some LHC data. Throughout our study we remark the main features that are produced by the kinematical selection cuts that are applied to the photons. In particular, we examine soft-gluon singularities that appear in the perturbative computations of the invariant mass distribution of the photon pair, the transverse-momentum spectra of the photons, and the fiducial cross section with asymmetric and symmetric photon transverse-momentum cuts, and we present their behaviour in analytic form.

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