Implementation of Precision Parton Shower Physics into the Herwig Event Generator for LHC Simulation

在高能物理中，我们通常对具有高动量转移的部分子(夸克和胶子)之间的相互作用感兴趣，产生新的粒子，如希格斯玻色子或超对称伙伴，或更常见的粒子，如顶夸克。这些衰变产生更多的部分子。然而，部分粒子不能自由传播，而是被限制在强子中，强子是与碰撞区域周围的探测器相互作用的粒子。通过这个过程，几个硬部子演化成一个由数百个强子组成的系统，这个过程太复杂了，无法进行解析计算，必须用蒙特卡罗技术进行数值模拟。如果没有蒙特卡罗事件发生器来模拟它们，任何试图理解大型强子对撞机或其他高能对撞机实验数据的尝试都是完全不可能的。Herwig事件产生器是大型强子对撞机和其他高能粒子物理实验中仅有的三个用于模拟事件的设备之一。这些事件产生器的一个关键组件是一种算法，该算法将高动量转移碰撞中产生的部分子向下演化到它们产生强子的能量尺度，称为部分子簇射算法。在过去的十年里，对部分子簇射物理的理论理解已经取得了很大的进展，这个博士项目的主要目的是利用这种理解来提高Herwig的部分子簇射算法的精度，从而提高它对大型强子对撞机事件模拟的准确性。

In high energy physics we are usually interested in interactions between partons (quarks and gluons) with high momentum transfer, producing new particles like the Higgs boson or supersymmetric partners, or more familiar ones like the top quark. These decay to produce further partons. However, partons cannot propagate freely but are confined into hadrons, the particles that interact with the detectors around the collision region. This process by which a few hard partons evolve into a system of hundreds of hadrons is far too complicated to calculate analytically and must be modelled numerically, with Monte Carlo techniques. Any attempt to understand the data from the LHC or other high energy collider experiments would be completely impossible without Monte Carlo event generators that simulate them. The Herwig event generator is one of only three used to simulate events at the LHC and other high energy particle physics experiments.A key component of these event generators is the algorithm to evolve the partons produced in the high momentum transfer collision down to the energy scale where they produce hadrons, called a parton shower algorithm. Great progress in the theoretical understanding of parton shower physics has been made over the last ten years and the main aim of this PhD project is to use that understanding to improve the precision of Herwig's parton shower algorithm and thereby the accuracy of its simulation of LHC events.