T2K construction - bridging funds

了解中微子的性质及其在宇宙中的作用，回答了我们目前知识前沿之外的问题。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展。基于这种理解，一个框架，粒子物理学的标准模型，能够描述观察到的粒子和相互作用的几个基本的相互作用和基本粒子的全部品种，已经开发出来。标准模型是在20世纪60年代基于现有基本粒子的现有知识制定的。标准模型的科学价值不仅在于它能够描述宇宙基本成分的基本性质，而且还在于它在与基于广义相对论的天体物理和宇宙学模型一起使用时，在宇宙学尺度上描述宇宙性质的成功。然而，标准模型缺陷的第一个也是最显著的证据来自中微子。在过去十年中发展的实验图像与三个中微子家族经历振荡是一致的，即具有特定轻子味道的中微子后来可以被测量为具有不同的味道，这只有在中微子具有质量和混合时才能发生。探测中微子是非常困难的，因为它们与物质的相互作用非常弱，因此需要高灵敏度的探测器来探测它们。T2 K实验将包括在J-PARC（东海）的50 GeV质子同步加速器上产生的世界上最高强度的μ介子中微子束，该束被引导到距离J-PARC 295公里的远探测器Super-Kamiokande。目前正在建造一个距离源仅约280米的近距离探测器，以便在振荡发生之前测量光束谱，并由超级神冈收集事件。近端探测器在T2 K中扮演着关键的角色，因为只有知道中微子流在振荡发生之前的成分，我们才能理解在远端探测器上得到的结果。英国在T2 K中发挥着关键作用，特别是在近探测器的建造方面。目前的赠款是需要完成近探测器，执行几个关键作用的电磁量能器的建设。这笔赠款是针对已经批准的“过渡”资金，用于支持英国在T2 K建设中承担的责任。

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.