T2K construction - bridging funds

了解中微子的性质及其在宇宙中的作用，回答了超出我们目前知识前沿的问题。在过去的几十年里，粒子物理学在最基本的层面上理解自然规律方面取得了前所未有的进步。在这一认识的基础上，发展了一个框架，即粒子物理标准模型，能够用几个基本相互作用和基本粒子来描述观察到的粒子和相互作用的全部种类。标准模型是上世纪60年代S根据现有基本粒子的现有知识而提出的。标准模型的科学价值不仅取决于它描述宇宙基本组成部分的基本性质的能力，而且还在于它在与基于广义相对论的天体物理和宇宙模型一起使用时，成功地描述了宇宙尺度上的性质。然而，标准模型缺陷的第一个也是最明显的证据来自中微子。过去十年发展的实验图景与经历振荡的三个中微子家族是一致的，即以特定轻子性质产生的中微子稍后可以测量出具有不同性质的中微子，这只有在中微子具有质量和混合时才能发生。探测中微子非常困难，因为它们与物质的相互作用非常弱，因此需要一个高灵敏度的探测器来探测它们。T2K实验将由位于J-PARC(东海)的50GeV质子同步加速器产生的世界上最高强度的Muon中微子光束对准距离J-PARC 295公里的远探测器Super-Kamiokande。正在建造一个距离震源仅约280米的近探测器，以便在振荡发生之前测量光束光谱，并由超级神冈收集事件。近探测器在T2K中起着关键作用，因为只有在振荡发生之前知道中微子通量的组成，我们才能理解在远探测器上获得的结果。英国在T2K中发挥着关键作用，特别是在NEAR探测器的建造方面。目前的赠款是完成NEAR探测器所需的，它为建造电磁量热计发挥了几个关键作用。这笔赠款与已经批准的支持英国在T2K建设中承担责任的“过渡性”资金背道而驰。

Understanding the nature of neutrinos and their role in the Universe answers questions beyond the current frontier of our knowledge. During the past few decades, particle physics has made unprecedented progress in understanding the laws of nature at the most fundamental level. Based on this understanding, a framework, the Standard Model of Particle Physics, capable of describing the whole variety of observed particles and interactions in terms of a few fundamental interactions and elementary particles, has been developed. The Standard Model was formulated in the 1960's based on the current knowledge of the existing elementary particles. The scientific value of the Standard Model rests not only on its ability to describe the fundamental properties of the elementary components of the Universe, but also on its success in describing properties of the Universe on cosmological scales, when used together with astrophysical and cosmological models based on general relativity. However, the first and most striking evidence of a shortcoming of the Standard Model comes from neutrinos. The experimental picture developed in the last ten years is consistent with three neutrino families undergoing oscillations, i.e. neutrinos created with a specific lepton flavour can later be measured to have a different flavour, which can only happen if neutrinos have masses and mix. Detecting neutrinos is very difficult as they interact very weakly with matter, so a detector with high sensitivity is required to detect them. The T2K experiment will consist of the world highest intensity muon neutrino beam produced at the 50 GeV Proton-Synchrotron at J-PARC (Tokai) being directed at a far detector, Super-Kamiokande, 295 Km away from J-PARC. A near detector, only about 280 m away from the source, is being constructed to measure the beam spectrum before the oscillations take place and the events are collected by Super-Kamiokande. The near detector has a critical role within T2K, since only with the knowledge of the composition of the neutrino flux before the oscillation takes place, can we understand the results obtained at the far detector. UK has a critical role within T2K and particularly the construction of the near detector. The current grant is needed for the completion of the near detector, performing several crucial roles for the construction of the electromagnetic calorimeter. This grant is against already approved 'bridging' funds for supporting the responsibilities taken by UK in the T2K construction.