Improving new physics searches with precision: Sudakov logarithms up to the two-loop level

大型强子对撞机(LHC)正在进行的实验的一个主要目的是寻找标准模型(SM)以外的现象。这些现象非常难得到--由于SM相互作用，新物理过程的极小事故率通常会被巨大的背景所淹没。事实上，在新的共振方面没有明显的新物理迹象，我们需要在非常复杂的终态测量的分布的尾部寻找非常小的百分比水平的偏差。在实验上，百分比级的精度将在不久的将来实现。然而，在理论预测中匹配这种非凡的精度是一个真正的挑战，需要在微扰理论中纳入更高阶的修正。在像LHC这样的强子对撞机上，我们主要关注高阶QCD校正，以便改进我们的理论模型。然而，由于苏达科夫对数的出现，远高于电弱(EW)尺度的高阶EW修正被强烈地增强，该对数是普遍存在的，由以给定微扰顺序贡献的回路幅度的明确结构产生。这些修正很容易达到与强子对撞机上的QCD高阶修正类似的水平。由于最近在次要顺序电子战修正的自动化方面取得的进展，现在可以评估任何直到高粒子多重数的SM过程，包括电子战修正。为了进一步改进预测，特别是对电子战改正作出可靠的不确定性估计，手头的项目应开发一个自动执行的Denner-Pozzorini算法，用于计算电子战苏达科夫对数，最高可达两环。作为第一步，应该预见到单环EW苏达科夫对数的实现，这在文献中已经存在，因此可以很容易地验证。该实现依赖于EW苏达科夫对数相对于Born过程的因式分解，直到倒数第二对数阶。一旦描述的实现可用，将进行现象学研究，利用新的档案精度和对理论不确定性的控制。特别是，这将涉及矢量玻色子融合和矢量玻色子散射拓扑中矢量玻色子的产生，这两种拓扑都允许对新物理进行严格的间接搜索。

A major aim of the ongoing experiments at the Large Hadron Collider (LHC) is the hunt for phenomena beyond the Standard Model (SM). These phenomena are extremely hard to come by - very small event rates for new physics processes are typically swamped by enormous backgrounds due to SM interactions. In fact, without a clear sign of new physics in terms of new resonances, we are required to look for very small percent-level deviations in the tails of distributions measured in very complex final states. Experimentally, percent-level precision will be achievable in the near future. However, matching this remarkable precision in theory predictions is a true challenge that requires to incorporate higher-order corrections in perturbation theory. At hadron colliders like the LHC we are primarily concerned with higher-order QCD corrections in order to improve our theoretical modelling. However, far above the electroweak (EW) scale higher-order EW corrections are strongly enhanced due to the appearance of Sudakov logarithms, which are universal and generated by well-defined structures of the contributing loop amplitudes at a given perturbative order. These corrections can easily reach a similar level as QCD higher-order corrections at hadron colliders. Thanks to recent advances in the automation of next-to-leading order EW corrections any SM process up to high particle multiplicity can now be evaluated including EW corrections. In order to further improve the predictions and in particular to arrive at reliable uncertainty estimates of the EW corrections the project at hand should develop an automated implementation of the Denner-Pozzorini algorithm for the calculation of EW Sudakov logarithms up to the two-loop level. As a first step the implementation of one-loop EW Sudakov logarithms should be foreseen, which is already available in the literature and can thus easily be validated. The implementation relies on the factorization of EW Sudakov logarithms with respect to the Born process valid up to the next-to-next-to logarithmic order. Once the described implementation is available phenomenological studies will be performed exploiting the newly archive precision and control of theoretical uncertainties. In particular this will concern the production of vector bosons in the vector-boson-fusion and vector-boson-scattering topologies, which both allow for stringent indirect searches for new physics.