T2K construction - bridging funds

了解中微子的本质及其在宇宙中的作用，可以回答超出我们目前知识前沿的问题。在过去的几十年里，粒子物理学在理解最基本的自然规律方面取得了前所未有的进步。基于这种理解，一个框架，粒子物理学的标准模型，能够描述观察到的各种粒子和相互作用的一些基本相互作用和基本粒子，已经发展。标准模型是在20世纪60年代根据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组成部分的基本特性，而且还在于它在与基于广义相对论的天体物理学和宇宙学模型一起使用时，成功地描述了宇宙尺度上的宇宙特性。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经历振荡的三个中微子家族是一致的，即具有特定轻子风味的中微子稍后可以被测量为具有不同风味，这只有在中微子具有质量并混合的情况下才会发生。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，所以需要一个高灵敏度的探测器来探测它们。T2K实验将由J-PARC （Tokai）的50 GeV质子同步加速器产生的世界上最高强度的μ子中微子束组成，这些中微子束将被引导到距离J-PARC 295公里远的超级神冈探测器上。一个距离源仅280米的近距离探测器正在建造中，用于测量振荡发生前的波束光谱，并由超级神冈探测器收集这些事件。近距离探测器在T2K中起着至关重要的作用，因为只有在振荡发生之前了解中微子通量的组成，我们才能理解远距离探测器获得的结果。英国在T2K，特别是近距离探测器的建设中发挥着关键作用。目前的拨款需要完成近距离探测器，在电磁量热计的建设中发挥几个关键作用。这笔拨款与已经批准的用于支持英国在T2K建设中所承担责任的“过渡性”资金相悖。

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.