Central Exclusive Production and Spectroscopy Studies at LHCb

在欧洲核子研究中心（CERN）的大型强子对撞机（Large Hadron Collider）上进行的大型强子对撞机（LHCb）实验中，反向循环的质子束以每秒数百万次的速度相互穿过。在大多数这样的传递中，碰撞发生在质子内部的夸克或胶子相互作用中，分裂母体，并与许多其他粒子一起产生新的感兴趣的状态。大型强子对撞机使用这种“非弹性”相互作用来研究cp违逆现象，而大型强子对撞机的其他实验也得益于这类相互作用来发现希格斯玻色子。然而，其他类型的相互作用也会发生；一个非常有趣的例子是所谓的中央独家生产。在中心独占生产中，质子相互作用，释放出一种称为玻介子的胶子系统。质子本身保持完整，并以最小的偏转继续它们的旅程，就好像它们只是“擦了擦肩膀”。然而，pomerons融合在一起并产生一个新的状态，然后在探测器中衰减。与通常看到的大量粒子的图像不同，一个美丽而干净的“事件”只产生了少数几个被观察到的粒子。测量这一过程的速率和特征，是检验我们对强作用力认识的重要而必要的检验。更重要的是，这个过程可能会产生难以在非弹性碰撞中分离和研究的状态。近年来，人们对奇异介子很感兴趣，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。中央独家生产为研究这些外来介子提供了一个极好的实验室。在即将于2015年春季开始的大型强子对撞机第二期运行中，将从大型强子对撞机数据中选择中央独家生产相互作用。然后对它们进行研究，并将其特征与预期进行比较。搜索将执行的存在，在这个数据集中的外来介子，并研究这些介子的性质。这项工作的一个重要挑战将是确保相互作用是真正的排他性，这意味着确保在实验中逃避检测的质子束附近没有产生额外的粒子。为此目的，在距离实验中心100米的隧道中安装了新的探测器，以便对这些额外的粒子敏感。操作这些探测器，确保它们表现良好，并充分利用它们在分析中提供的信息，将是研究计划的一个关键方面。

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.