Central Exclusive Production and Spectroscopy Studies at LHCb

在欧洲核子研究中心的大型强子对撞机上进行的LHCb实验中，反循环的质子束每秒相互穿过数百万次。在大多数这样的通过中，发生碰撞，其中质子内部的夸克或胶子相互作用，分裂父母，并产生新的感兴趣的状态，以及许多其他粒子。LHCb使用这种“非弹性”相互作用来研究CP破坏现象，LHC的其他实验也从这些相互作用中受益，发现了希格斯玻色子。然而，也存在其他类型的相互作用，其中一个非常有趣的例子是所谓的中心排他性产生，在中心排他性产生中，质子通过发射一个称为坡密子的胶子系统相互作用。质子本身保持完整，并以最小的偏转继续它们的旅程，就像它们只是“摩擦肩膀”一样。然而，pomeron融合在一起并产生一个新的状态，然后在检测器中衰变。而不是通常的图片的大量粒子被视为，一个美丽的干净的“事件”产生的只有少数粒子观察。测量这一过程的速率和特征是对我们理解强相互作用的重要和必要的检验。更重要的是，这一过程可能产生难以在非弹性碰撞中分离和研究的状态。近年来，人们对奇异介子产生了很大的兴趣，这是一类强相互作用的粒子，很难用夸克和反夸克的束缚系统的传统图像来解释，而是需要更复杂的成分排列。在即将到来的LHC运行2期间，由于开始在2015年春季，中央独占生产相互作用将从LHCb数据中选择。然后将对这些进行研究，并将其特征与预期进行比较。我们将对这组数据中奇异介子的存在进行量子化学计算，并研究这些介子的性质。这项工作的一个重要挑战是确保相互作用是真正排他性的，这意味着确保没有额外的粒子产生接近质子束，逃避实验中的检测。为此，在隧道中安装了新的探测器，距离实验最远可达100米，以便对这些额外的粒子敏感。操作这些探测器，确保它们运行良好，并充分利用它们在分析中提供的信息，将是研究方案的一个关键方面。

At the LHCb experiment, on the Large Hadron Collider at CERN, the counter-circulating beams of protons pass through each other many millions of times per second. In most of these passings, collisions occur in which the quarks or gluons inside the protons interact, splitting apart the parents, and produce new states of interest, together with many other particles. LHCb uses such 'inelastic' interactions to study the phenomenon of CP-violation, and the other experiments at the LHC have benefitted from these classes of interaction to discover the Higgs boson. Other categories of interaction occur however; one example of great interest is so-called Central Exclusive Production.In Central Exclusive Production the protons interact through both emitting a system of gluons termed the pomeron. The protons themselves remain intact, and continue their journey with minimal deflection, much as if they had only 'rubbed shoulders'. The pomerons however fuse together and produce a new state which then decays in the detector. Rather than the usual picture of a multitude of particles being seen, a beautifully clean 'event' is produced with only a handful of particles observed. Measuring the rate and characteristics of this process is an important and necessary test of our understanding of the strong force. Even more importantly, the process may produce states which are hard to isolate and study in inelastic collisions. There has been much interest in recent years in exotic mesons - a class of strongly interacting particles that are hard to explain by the conventional picture of a bound system of quark and anti-quark, but rather requires a more complex arrangement of constituents. Central Exclusive Production provides an excellent laboratory to study these exotic mesons.During the forthcoming LHC run 2, due to begin in Spring 2015, Central Exclusive Production interactions will be selected from the LHCb data. These will then be studied and their characteristics compared with expectation. Searches will be performed for the presence of exotic mesons in this data set, and the properties of these mesons studied. An important challenge in this work will be to ensure that the interactions are truly exclusive, which means ensuring no additional particles have been produced close to the proton beams that evade detection in the experiment. For this purpose, new detectors have been installed in the tunnel at distances up to 100 m away from the experiment, in order to be sensitive to such additional particles. Operating these detectors, ensuring that they perform well, and making best use of the information they provide in the analysis, will be a critical aspect of the research programme.