Double Parton Scattering at the LHC and Beyond

大多数改进质子-质子碰撞理论预测的工作都集中在改进对最高能量的“初级”部分子-部分子碰撞的描述上。然而，附加的部分子-部分子碰撞可以而且确实会发生。在单个质子-质子碰撞中有两个高能部分子-部分子碰撞的情况被称为双部分子散射(DPS)。这个过程可以在某些运动学区域和/或某些过程中与单次散射的速率竞争，揭示了关于质子结构的新信息，并随着对撞机能量的增加而变得更加重要。这个项目的目的是开发工具来对DPS进行预测，这些工具首次基于第一原理QCD理论。这项工作的一个主要组成部分将是进一步发展DPS的蒙特卡罗模拟，例如，包括某些量子关联效应、强子化和不等尺度过程。然后，这些工具将被用于对DPS可以发挥重要作用的关键LHC工艺进行预测，例如同号WW、多重口味和4个喷气生产工艺。这项研究的一个重要目标将是找到对完整QCD框架的预测与以前使用的简化DPS模型获得的预测不同的测量结果-这些差异将由只存在于前者中的部间关联和QCD效应引起，并且对于通过实验进行搜索具有内在的兴趣，以及了解对于其他搜索的DPS背景的准确描述是重要的。这个项目的最终目标将是通过结合所有关于DPS的非微扰部分的已知信息来改进DPS预测中的非微扰模型，这些信息来自理论约束、晶格计算和实验。

Most of the work on improving theoretical predictions for proton-proton collisions has focussed on improving the description of the highest-energy "primary" parton-parton collision. However, additional parton-parton collisions can and do occur. The case in which we have two high-energy parton-parton collisions in an individual proton-proton collision is known as double parton scattering (DPS). This process can compete in rate with single scattering in certain kinematic regions and/or for certain processes, reveals new information on proton structure, and becomes more important as collider energy grows. The aim of this project is to develop tools to make predictions for DPS that are based, for the first time, on first principles QCD theory. A major component of this work will be the further development of the Monte Carlo simulation of DPS, dShower - for example, to include certain quantum correlation effects, hadronisation, and unequal scale processes. These tools will then be applied to make predictions for key LHC processes where DPS can play an important role, such as the same-sign WW, multiple heavy flavour and 4 jet production processes. An important goal in this study will be to find measurements where the predictions of the full QCD framework differ from those obtained by the simplified DPS models used previously - these differences will be caused by inter-parton correlations and QCD effects present only in the former, and are both intrinsically interesting to search for experimentally, as well as being important to know for the accurate description of DPS backgrounds to other searches. A final goal in this project will be to improve the nonperturbative modelling in DPS predictions, by combining all known information about the nonperturbative part of DPS arising from theoretical constraints, lattice calculations, and experiment.