Global Fits for Parton Distributions and Implications for Hadron Collider Physics

为了达到尽可能高的能量，目前的粒子对撞机，汉堡的DESY电子-正电子对撞机和芝加哥附近的Tevatron质子-反质子对撞机，至少有一个质子作为碰撞粒子。质子是通过强力相互作用的粒子，是复合粒子，因为强力将基本成分--部分粒子-可能是夸克或胶子--结合到这些复合粒子中。欧洲核子研究中心目前正在建造的对撞机--大型强子对撞机(LHC)将是一台质子-质子对撞机。大型强子对撞机将是有史以来最大的能量超过7倍的粒子对撞机，它将使我们能够看到粒子物理标准模型中缺失的粒子-希格斯玻色子-是否存在-以及探测标准模型之外的第一个物理迹象，例如，超对称性，其中每个标准模型粒子都有一个超对称伙伴。在低能时，我们认为部子被束缚在质子内部，但在很高的能量下，强耦合变得更弱，碰撞质子之间的相互作用可以被认为是每个质子中的部子之间的相互作用，这可以计算为强耦合常数的展开。因此，为了理解任何强子对撞机实验的结果，我们必须首先了解质子是如何由其部分子组分组成的。在某种程度上，这是可以计算的，但强耦合使一些展开定义得不好，一些信息可以从实验中确定。因此，人们必须进行足够的独立实验，并尽可能准确地使用强力理论(量子色动力学-QCD)中的理论计算，以胶子和六种夸克(上、下、奇异、魅力、底部和顶部)的形式来确定质子的组成。这需要使用各种实验的数据，并且必须检查所有的数据是否与部分子和QCD理论一致，从而非常准确地测试QCD，并测量强耦合。一旦确定了一致性，这些部分子就可以用来预测使用质子的任何其他过程。这可以是标准模型粒子之外的产物，也可以是标准模型过程的产物，后者往往掩盖了前者。建议的项目是通过纳入新的理论计算，例如耦合中的更高阶数，更精确地包括重粒子修正，以及通过包括来自现有对撞机和即将到来的大型强子对撞机的新过程，来改进对撞机物理中部分子分布及其后果的确定。这些新的理论发展和新的数据流入将意味着我们需要大量的工作来获得最好的部分。然而，如果要正确解释数据，这是至关重要的，因此，如果我们要增加对标准模型的理解，并且非常重要的是，试图探索它以外的物理。

In order to reach the highest possible energies, the current particle colliders, the DESY electron-positron collider at Hamburg and the Tevatron proton-antiproton collider near Chicago, have protons as at least one of their colliding particles. Protons are particles which interact via the strong force, and are composite particles because the strong force binds the fundamental constituents, partons - which may be quarks or gluons, into these composite particles. The collider currently under construction at CERN, the Large Hadron Collider (LHC) will be a proton-proton collider. The LHC will be the largest energy particle collider ever created by a factor of more than 7, and will enable us to see if the missing particle within the Standard Model of particle physics, the Higgs boson exists - as well as to detect the first signs of physics beyond the Standard Model, for example, Supersymmetry, where each Standard Model particle has a supersymmetric partner. At low energies we think of the partons being bound within the proton, but at very high energies the strong coupling becomes weaker and the interactions of colliding protons can be thought of as interactions between the partons in each proton, which may be calculated as an expansion in the strong coupling constant. Hence, in order to understand the results of any hadron collider experiments, one must first understand how the proton is made up out of its partonic constituents. To a certain degree this can be calculated, but strong coupling makes some expansions badly defined, and some of the information can be determined from experiment. Therefore one must perform enough independent experiments, and use the theoretical calculations within the theory of the strong force (Quantum Chromodynamics - QCD) as accurately as possible, to determine the composition of the proton in terms of the gluons and the six flavours of quarks (up, down, strange, charm, bottom and top). This requires use of data from a variety of experiments, and it must be checked that all pieces of data are consistent with the partons and QCD theory, hence testing QCD to great accuracy, and measuring the strong coupling. Once consistency is determined these partons may be used to predict any other process using the protons. This can be the production of beyomd the Standard Model particles, or for Standard Model processes, where the latter often mask the former. The project proposed is to improve the determination of parton distributions and their consequences for collider physics, by incorporating new theoretical calculations, e.g. higher order in the coupling, more precise inclusion of heavy particle corrections, and by the inclusion of new processes, both from the existing colliders and from the forthcoming LHC. These new theoretical developments and the new influx of data will mean we require a lot of work to obtain the best partons. However, this is essential if the data are to be interpreted properly, and hence, if we are to increase our understanding of the Standard Model, and very importantly, try to search for the physics beyond it.