Development of a Focussing Disc DIRC for PANDA at FAIR

自然界有四种基本力，其中最常见的是重力和电磁力。前者让苹果从树上掉下来，让行星围绕太阳运行；后者让分子聚集在一起，操控iPod。第三种力是所谓的弱力，负责β衰变过程，例如正电子发射断层扫描中正电子的产生。第四种力之所以被称为强力，是因为它比弱力强13个数量级(或十万亿倍)。这种强大的力负责将原子核结合在一起。在比原子核更小的尺度上，它是由夸克和胶子形成强子的相互作用，因此是宇宙中大多数可观察到的质量的原因。量子色动力学(QCD)被广泛认为是描述强相互作用的基本理论；最近的诺贝尔奖(2004年，Gross，Politzer，Wilczek)被授予这一理论的发展。反质子和离子研究设施，FAIL，是一个新的国际加速器设施，将设在德国达姆施塔特的GSI实验室现场。GSI本身以发现一些超重元素而闻名，如110号元素、Darmstadtium元素。现有的GSI加速器将作为新设施的注射器。FAIR的主要加速器将是一台双环同步加速器，它将以相当大的能量提供前所未有的强度的离子束。可以产生强烈的次级光束--不稳定的原子核或反质子。存储冷却器环系统将使这些次级光束的质量--它们的能量扩散和发射度--得到极大的改善。熊猫博览会的旗舰实验之一将是QCD实验。它将位于新的高能储存环(HESR)，在那里，一束动量为1至15GeV/c的反质子束撞击目标。熊猫的主要研究课题将是：-Charmonium光谱学：对Charmonium态(具有魅力夸克的态)的精确测量将有助于了解强子质量的起源。此外，还可以研究夸克在强子中的禁闭机制。-胶球和混合体：介子的夸克模型图是它们由一个夸克和一个反夸克组成。QCD预测，可能有不同的组合不符合这个模型：有胶子激发的夸克，或者只有胶子的夸克。-质子结构：绘制出核子中夸克的空间和自旋分布将有助于更深入地了解强子结构。广交会项目于2007年11月正式启动，加速器将于2008年开工建设。这是在合作研究所之间分配实验建设任务的时间点。在这项提案中，我们正在申请资金来开发熊猫探测器的关键部件之一-粒子识别端盖圆盘DIRC，这是格拉斯哥-爱丁堡的创新设计，将成为世界上第一个此类探测器。我们在熊猫内部领导着这一项目，并在整体颗粒识别方面发挥着主导作用。这两个英国组织是熊猫实验的创始成员，该实验现在是一个国际合作项目，有来自17个国家的约400名成员。这项提议的资金将确保我们继续在设计和建造这一实验的重要部分方面发挥主导作用。

There are four fundamental forces in nature, of which gravity and electromagnetism are the most familiar. The former makes apples fall from trees and keeps planets in their orbits around the sun; the latter holds molecules together and operates iPods. The third force is the so-called weak force and is responsible for beta decay processes, such as the creation of positrons in Positron Emission Tomography. The fourth force is called strong force because it is 13 orders of magnitude (or ten thousand billion times) stronger than the weak force. The strong force is responsible for binding together atomic nuclei. At an even smaller scale than nuclei, it is the interaction that forms hadrons from quarks and gluons, and is therefore responsible for most of the observable mass in the universe. Quantum Chromodynamics (QCD) is widely accepted as the fundamental theory describing the strong interaction; a recent Nobel Prize (2004, Gross, Politzer, Wilczek) was awarded for the development of this theory. The Facility for Antiproton and Ion Research, FAIR, is a new international accelerator facility, to be located on the site of the GSI laboratory in Darmstadt, Germany. GSI itself is well known for the discovery of some super-heavy elements, e.g. element 110, Darmstadtium. The existing GSI accelerators will serve as injectors for the new facility. The main accelerator of FAIR will be a double-ring synchrotron that will provide ion beams of unprecedented intensities at considerably increased energy. Intense secondary beams - unstable nuclei or antiprotons - can be produced. A system of storage-cooler rings will allow the quality of these secondary beams - their energy spread and emittance - to be drastically improved. One of the flagship experiments of FAIR, PANDA, will be a QCD experiment. It will be located in the new High Energy Storage Ring (HESR), where an anti-proton beam at momenta of 1 to 15 GeV/c impinges on a target. The main research topics at PANDA will be: - Charmonium spectroscopy: Precision measurements of charmonium states (states with charm quarks) will help to understand the origin of the masses of hadrons. In addition, the mechanism of confinement of quarks in hadrons can be investigated. -Glueballs and Hybrids: The quark model picture of mesons is that they consist of a quark and an antiquark. QCD predicts that there could be different combinations that do not fit this model: quarks with gluonic excitations, or gluons only. -Proton structure: Mapping out the spatial and spin distributions of quarks in the nucleon will lead to a deeper understanding of hadron structure. The FAIR project was launched formally in November 2007, and the construction of the accelerators will commence in 2008. This is the point in time where the construction tasks for the experiments are being distributed among the collaborating institutes. In this proposal, we are applying for funding to develop one of the crucial parts of the PANDA detector, the particle identification endcap disc DIRC, which is an innovative Glasgow-Edinburgh design and will be the first detector of its kind world-wide. We are leading this project within PANDA and are also playing a leading role in the overall particle identification. The UK groups are founding members of the PANDA experiment, now an international collaboration with ca. 400 members from 17 countries. The funding of this proposal will ensure that we continue playing a leading role in the design and construction of this vital part of the experiment.