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（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，或更熟悉的粒子，如顶夸克。这些物质会衰变产生更多的分子。然而，部分不能自由传播，而是被限制在强子中，强子是在碰撞区域周围与探测器相互作用的粒子。这个由几个硬粒子演化成数百个强子组成的系统的过程太复杂了，无法用分析方法计算，必须用蒙特卡罗技术进行数值模拟。如果没有蒙特卡洛事件生成器来模拟，任何理解LHC或其他高能对撞机实验数据的尝试都是完全不可能的。赫维希事件发生器是仅有的三个用于模拟大型强子对撞机和其他高能粒子物理实验的事件发生器之一。这些事件发生器的一个关键组成部分是将高动量转移碰撞中产生的粒子演化到产生强子的能量尺度的算法，称为粒子阵雨算法。在过去的十年里，人们对部分子淋浴物理的理论认识取得了很大的进步，本博士项目的主要目的是利用这一认识来提高Herwig的部分子淋浴算法的精度，从而提高其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.