RA post re Ken Long's MICE Spokesperson position

中微子是三种不同但相互关联的粒子；它们相互转化的能力让物理学家们第一次瞥见了物理学，他们知道这种物理学肯定超出了标准模型。研究它们的物理性质将加深我们对宇宙在大爆炸后如何发展的理解；目前物质和反物质之间的不对称是如何从大爆炸中同等数量的物质创造出来的；并帮助我们理解当超新星爆炸时会发生什么，向宇宙注入行星和生命本身形成所需的重元素。为了了解它们的性质，我们必须建造一台能够产生巨大数量的中微子的加速器。它们的能量必须在明确定义的极限之间，不同类型的混合物必须非常精确地知道。这种名为中微子工厂的设施将是革命性的，无论是从必须建造的粒子探测器的角度来看，还是从必须克服的工程问题的角度来看，建造一个中微子工厂都是具有挑战性的。这个项目需要全球范围的合作，来自英国的物理学家和工程师在其中发挥着主导作用。中微子是由一束介子产生的，而介子本身是由质子与金属靶碰撞产生的介子衰变而产生的。用这种方法产生的介子束很大，而且发散很大。要制造一束强烈的中微子，必须减小束流的大小和发散度。产生的束流可以被加速和存储，这样当µ子衰变时，就会产生一束高能量的中微子。在静止状态下，介子的寿命只有2.2微秒，即使它们被加速，并且它们的寿命因相对论效应而延长，也几乎没有时间来操纵它们，以便有效地加速它们。国际Muon电离冷却实验(MICE)合作正在建造一段加速器，旨在证明可以有效地减小Muon束的大小。MICE正在牛津郡的卢瑟福·阿普尔顿实验室建造。ISIS的加速器产生了一束介子束。介子一个接一个地通过实验。首先，在光谱仪中测量它们的位置和动量。然后，介子通过一个装满液氢的容器，在那里它们通过电离氢分子来释放能量。一个很短的加速器部分恢复能量，沿着束流方向加速粒子。这一过程的结果是减少了介子的随机侧向运动，从而对光束进行冷却；执行冷却的系统被称为冷却室。第一阶段是建立一个系统，能够在进入冷却通道之前产生尺寸和发散可以调整的介子束。这项工作已经完成。第二个阶段是完成冷却通道本身的建造，并提供一个系统来非常准确地测量每个介子在通过冷却通道之前和之后的位置和动量。通过观察在许多不同条件下产生的许多介子，就有可能确定该通道产生了多少冷却。这项实验正在突破材料、磁体和冷却技术的可能，是粒子物理学家和加速器物理学家的合作，将展示英国主办科学和工程前沿实验的能力。

Neutrinos are three different but related particles; their ability to turn into each other has given physicists their first glimpse of the physics which they know must lie beyond the Standard Model. Investigation of the physics which underlies their properties will: deepen our understanding of how the Universe developed after the Big Bang; how the current asymmetry between matter and anti-matter developed from a situation where they were created in equal amounts in the Big Bang; and help us to understand what happens when a supernova explodes showering the cosmos with the heavy elements necessary for planets and life itself to form. In order to understand their properties, we must build an accelerator capable of creating neutrinos in immense numbers. They must have energy between well-defined limits and the mixture of different types must be very precisely known. Such a facility, known as the Neutrino Factory, would be revolutionary and to build one is challenging, both from the point of view of the particle detectors that must be built, and the engineering problems that must be overcome. This programme needs a worldwide collaboration and it is one in which physicists and engineers from the UK are playing a leading role.Neutrinos are created from a beam of muons and the muons themselves are produced from the decay of pions produced by the collision of protons with a metal target. The muon beam produced in this way is large and highly divergent. To make an intense beam of neutrinos requires that the size and divergence of the beam must be reduced. The resulting beam can be accelerated and stored such that when the muons decay an intense beam of high-energy neutrinos is produced. The muons only live for 2.2 microseconds when at rest, and even when they are accelerated and their lifetime is extended by the effect of relativity, there is little time to manipulate them so that they can be accelerated efficiently. The international Muon Ionization Cooling Experiment (MICE) collaboration is constructing a section of accelerator that has been designed to demonstrate that the size of the muon beam an be reduced efficiently.MICE is under construction at the Rutherford Appleton Laboratory in Oxfordshire. A beam of muons is created by the ISIS accelerator. Muons pass one by one through the experiment. First their position and momentum is measured in a spectrometer. Then, the muons pass through a vessel filled with liquid hydrogen, where they loose energy by ionising the hydrogen molecules. A short accelerator section restores the energy, accelerating the particles along the beam direction. The result of thus process is to reduce the random sideways motion of the muons, thereby "cooling" the beam; the system which performs the cooling is known as the cooling cell.The first stage was to build a system capable of producing a muon beam whose size and divergence could be adjusted before it enters the cooling channel. This has been completed. The second stage is to finish construction of the cooling channel itself and to provide a system to measure very accurately the position and momentum of each muon before and after it has passed through the cooling channel. By looking at many muons produced in many different conditions, it will be possible to determine how much cooling has been produced by the channel. This experiment which is pushing the boundaries of what is possible with materials, magnets and cooling technologies, is a collaboration between particle physicists and accelerator physicists and will demonstrate the UK's ability to host an experiment at the forefront of science and engineering.