Studies in Charm Physics

标准模型（SM）成功地描述了所有相关的实验现象，因此被普遍接受为基本粒子物理学的基本理论。尽管SM取得了成功，但它留下了许多未解之谜。这些可以分为两大类：一类是与未探索的能量尺度上可能的新物理有关的学科，另一类是与量子色动力学（QCD）有关的物理学，强相互作用的基本理论。SM描述的粒子物理能量高达100 GeV（千兆电子伏特）左右。预计新的粒子和新的相互作用将出现在更高的能量尺度上，比如1tev（特拉电子伏特）。这些新粒子和新的相互作用可能需要解决SM内部的一些不一致，并最终统一所有相互作用。这些物理问题都属于第一类，将在2008年开始运行的大型强子对撞机上进行实验来解决。第二类悬而未决的问题包括那些需要QCD的问题。QCD作为强相互作用的基本理论，在短距离上得到了很好的验证，但在远距离上，所谓的非微扰效应变得很重要，而且这些还没有得到很好的理解。这些效应对于粒子物理领域来说是非常基础的，包括强子（具有强相互作用的粒子）的结构和强子态的谱。高光度的低能耗设施可以解决这些问题。其中，北京电子正电子对撞机II （BEPCII）将是一个重要的贡献者，它将在2 GeV到4.6 GeV的能量范围内工作。这是因为它跨越了可以探测短距离和远距离效应的能量范围。BES III是基于中国BEPCII e+e对撞机的通用探测器。BEPCII的亮度比它的前身提高了100倍，最近人们对强子光谱和粲夸克物理的兴趣也有所恢复。这种复兴在一定程度上是由粲粒子混合的实验报告和其他窄宽度粲态的发现所推动的，再加上B介子工厂中大量的类粲态。与此同时，一种被称为晶格量子色动力学（QCD）的计算机密集型技术正在成熟，我们正在进入一个新的时代，从晶格量子色动力学中得出的精确、定量的预测可以通过实验测量进行测试。在北京的BEPCII对撞机上进行的BES-III实验于2008年夏季开始运行，将积累与这些主题相关的大量数据样本。结合目前CLEO-c实验的结果，BES-III将以前所未有的高精度详细研究粲态和粲介子衰变中的光强子光谱。许多高精度的测量将被完成。BES-III分析可能是决定最近观察到的魅力混合迹象是否真的是由于新的物理现象的关键。精确的晶格QCD计算提供了在一些大型强子对撞机无法达到的质量范围内探测带电希格斯扇区的机会。

The Standard Model (SM) has been successful at describing all relevant experimental phenomena and, thus, has been generally accepted as the fundamental theory of elementary particle physics. Despite its success, the SM leaves many unanswered questions.These can be classified into two main categories: one for subjects related to possible new physics at unexplored energy scales and the other for physics mostly related to Quantum Chromodynamics (QCD), the fundamental theory of the strong interactions.The SM describes particle physics up to energies of around 100 GeV (Giga electron Volts). It is expected that new particles and new interactions will appear at some higher energy scale, say 1 TeV (Tera electron Volts) . Those new particles and new interactions are presumably needed to solve some inconsistencies within the SM and for the ultimate unification of all interactions. Such physics issues all belong to the first category, and will be addressed by experiments at the LHC, which will start operation in 2008. The second category of unanswered questions includes those requiring QCD. QCD, as the fundamental theory of the strong interactions, is well tested at short distances, but at long distances so-called nonperturbative effects become important and these are not well understood. These effects are very basic to the field of particle physics and include e.g., the structure of hadrons (particles with strong interactions) and the spectrum of hadronic states. Lower energy facilities with high luminosity can address these questions. Among these, the Beijing Electron Positron Collider II (BEPCII), which will operate in the 2 GeV to 4.6 GeV energy range, will be an important contributor. This is because it spans the energy range where both short-distance and long-distance effects can be probed.BES III is a general-purpose detector based at the BEPCII e+e- collider in China. BEPCII has a 100x improvement in its luminosity over its predecessor,There has also recently been a renewal of interest in the subjects of hadron spectroscopy and charm quark physics. This renaissance has beendriven in part by experimental reports of charm particle mixing and the discovery of additional narrow-width charm states, plus a plethora of charmonium-like states at the B meson factories. At the same time, a computer intensive technique called lattice Quantum Chromodynamics (QCD) is now coming of age, and we are entering a new era when precise, quantitative predictions from lattice QCD can be tested against experimental measurements. The BES-III experiment at the BEPCII collider in Beijing, which started operation in summer 2008, will accumulate huge data samples relating to these topics. Coupled with currently available results from the (closing) CLEO-c experiment, BES-III will make it possible to study in detail, and with unprecedented high precision, light hadron spectroscopy in the decays of charmonium states and charmed mesons. Many high precision measurements will be accomplished. BES-III analyses are likely to be essential in deciding if recently observed signs of charm mixing are actually due to new physics or not. And precision lattice QCD calculations provide the opportunity to probe the charged Higgs sector in some mass ranges that will be inaccessible to the LHC.