Higher order QCD calculations for collider phenomenology

在欧洲核子研究中心（CERN）的大型强子对撞机（LHC）测量的大多数碰撞中，都会产生大量的粒子。然而，对于一类特殊的事件，即所谓的排他性事件，情况并非如此。如果潜在的硬散射是通过颜色中性交换发生的，比如光子或单线态的胶子系统。为了更好地理解这些事件，需要进行高阶计算。最近这样的工作已经完成（部分在利物浦），用于矢量介子光产生的特殊情况，随后在LHCb的测量证实了这些预测。拟议的研究项目是对更复杂的开放夸克（或喷流）产生情况进行计算，并可能对包括W、Z或希格斯玻色子在内的电产生或过程进行计算。这不仅将导致对强相互作用的更深层次的理解，更好地约束质子（和重离子）的部分子分布函数，而且还将为粒子物理标准模型（SM）之外的物理学提供搜索渠道。第二个可能的项目，已经与Chris Flett讨论过，是参与微扰QCD的四阶计算，由NIKHEF（阿姆斯特丹）的Jos Vermaseren ERC小组与利物浦的Andreas Vogt一起执行，Andreas Vogt将是第二主管。这些计算是理论高能物理中符号计算的前沿，其主要目的是约束并最终计算质子中夸克和胶子分布的尺度依赖性的次-次-次-次-前序（NNNLO）分裂函数。例如，为了在欧洲核子研究中心的大型强子对撞机中产生希格斯粒子的横截面，以及为了最好地确定强耦合常数（SM的基本参数之一），需要进行NNNLO计算。

In most collisions measured at the Large Hadron Collider (LHC) at CERN, a very large number of particles are produced. However, for a special class of events, so-called exclusive events, this is not the case. This can happen if the underlying hard scattering occurs through colour neutral exchanges, like photons or systems of gluons in the colour singlet state. To better understand these events, higher order calculations are required. Recently such work has been done (in part in Liverpool) for the special case of vector meson photo-production, and subsequently measurements at the LHCb have confirmed the predictions. The proposed research project is to perform calculations for the more complicated case of open quark (or jet) production, and possibly to electro-production or processes including W, Z or Higgs bosons. This will not only lead to a deeper understand of the strong interaction and to better constrain the parton distributions functions of the proton (and heavy ions), but will also provide search channels for physics beyond the Standard Model (SM) of particle physics.A second possible project, already discussed with Chris Flett, is to participate in fourth-order calculations in perturbative QCD, performed by the ERC group of Jos Vermaseren at NIKHEF (Amsterdam) together with Andreas Vogt in Liverpool who will be the second supervisor. The main thrust of these calculations, which are at the cutting edge of symbolic computation in theoretical high-energy physics, is to constrain and ultimately calculate the next-to-next-to-next-to-leading order (NNNLO) splitting functions for the scale dependence of the quark and gluon distributions in the proton. NNNLO calculations are required, for example, for the cross section for Higgs production at the LHC at CERN, and for the best possible determination of the strong coupling constant which is one of the fundamental parameters of the SM.