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，在汉堡的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它们的碰撞粒子。质子是通过强力相互作用的粒子，并且是复合粒子，因为强力将基本成分，部分子-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大型强子对撞机（LHC）将是一个质子-质子对撞机。大型强子对撞机将是有史以来最大的能量粒子对撞机超过7倍，并将使我们能够看到粒子物理学标准模型中缺失的粒子，希格斯玻色子是否存在-以及检测标准模型之外的物理学的第一个迹象，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。在低能量时，我们认为部分子被束缚在质子内，但在非常高的能量时，强耦合变得较弱，碰撞质子的相互作用可以被认为是每个质子中部分子之间的相互作用，这可以被计算为强耦合常数的扩展。因此，为了理解任何强子对撞机实验的结果，我们必须首先理解质子是如何由其部分子成分组成的。在某种程度上，这是可以计算的，但是强耦合使得一些展开式定义不好，并且一些信息可以从实验中确定。因此，必须进行足够的独立实验，并尽可能准确地使用强作用力理论（量子色动力学- QCD）中的理论计算，以确定质子的胶子和六种夸克（上，下，奇怪，魅力，底部和顶部）的组成。这需要使用来自各种实验的数据，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任何其他使用质子的过程。这可能是超越标准模型的粒子的产生，或者是标准模型过程，后者经常掩盖前者。拟议的项目是通过纳入新的理论计算，例如耦合中的高阶，更精确地包含重粒子修正，以及通过包含来自现有对撞机和即将到来的LHC的新过程，来改进对部分子分布及其对对撞机物理学的影响的确定。这些新的理论发展和新的数据涌入意味着我们需要做大量的工作来获得最好的部分子。然而，这是必不可少的，如果数据要得到正确的解释，因此，如果我们要增加我们对标准模型的理解，非常重要的是，试图寻找超越它的物理学。

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.