Continuation of UK participation in the International Muon Ionization Cooling Experiment - Bridging Funds

中微子工厂是一种可能的未来加速器设施，它可以从储存环中的介子衰变中产生中微子束。来自中微子工厂的中微子束将具有最高的强度，并且可以以前所未有的精度进行控制。由于这些原因，中微子工厂有可能发现中微子和反中微子振荡之间可测量的差异，这可能是理解宇宙物质-反物质不对称之谜的关键。这种被称为CP违逆的现象在夸克扇区被观察到，但从未在中微子扇区被观察到。未来的中微子工厂将尽可能精确地确定中微子扇区的CP违逆。此外，中微子工厂可以作为建造μ子对撞机之前的第一阶段，该对撞机可以用于以终极精度测量希格斯玻色子的性质，并且可能达到高达6 GeV的能量，以便在最高能量前沿探索新的物理现象。中微子工厂和μ子对撞机都依赖于μ子的加速。为了能够创建μ子加速器设施，我们需要减小μ子束的大小，以便加速它。由于μ子在自己的静止框架内衰变在2微秒内，在μ子衰变之前减少μ子束相空间的唯一已知方法是使用电离冷却的概念，其中μ子在吸收体（如液氢或氢化锂（LiH））中损失能量，然后通过使用射频腔加速它们来恢复动量的纵向分量。国际μ子电离冷却实验（MICE）是电离冷却概念的工程演示。这个实验是在卢瑟福阿普尔顿实验室进行的，在这个实验中，一束μ子将在一个由三个吸收器和两个RF腔组成的μ子冷却室中冷却，该冷却室位于两个聚焦线圈磁铁的场中。使用超导螺线管内的闪烁光纤跟踪器在冷却通道前后测量光束的发射度，并使用飞行时间探测器，切伦科夫探测器和由闪烁纤维铅预浴探测器（命名为KL）和完全主动闪烁探测器组成的量热计系统来识别μ子，称为电子μ子游子（EMR）。在本提案中，我们的目标是在没有射频腔的情况下进行发射度降低的测量（MICE步骤IV），并在射频腔的情况下进行电离冷却的最终演示。该提案将于2016年4月至12月竞标9个月的资金，以填补目前的MICE第四阶段建设拨款（2016年3月结束）和电离冷却的最终演示（预计将持续到2019年）。

The Neutrino Factory is a possible future accelerator facility that creates beams of neutrinos from the decays of muons in a storage ring. The neutrino beams from a Neutrino Factory would have the highest intensity and can be controlled with unprecedented accuracy. For these reasons, the Neutrino Factory has the potential to discover measurable differences between neutrino and antineutrino oscillations, which could be the key to understanding the puzzle of the matter-antimatter asymmetry of the universe. This phenomenon, known as CP violation, has been observed in the quark sector but has never been seen in the neutrino sector. A future Neutrino Factory would determine CP violation in the neutrino sector with the best possible accuracy. Furthermore, a Neutrino factory could be used as a first stage before the construction of a Muon Collider, which could be used to measure the properties of the Higgs boson with the ultimate precision, and could potentially reach energies of up to 6 GeV, in order to explore new physics phenomena at the highest energy frontier.Both the Neutrino Factory and a Muon Collider rely on the acceleration of muons. To be able to create muon accelerator facilities, we require to reduce the size of the muon beam so that it may be accelerated. Since muons decay within 2 microseconds in their own rest frame, the only known way to reduce the phase space of the muon beam before the muons decay is to use the concept of ionisation cooling, in which the muons lose energy in an absorber such as liquid hydrogen or lithium hydride (LiH) and then recover the longitudinal component of the momentum by accelerating them using RF cavities. The international Muon Ionization Cooling Experiment (MICE) is an engineering demonstration of the concept of ionisation cooling. This experiment is being built at the Rutherford Appleton Laboratory, in which a beam of muons will be cooled in a muon cooling cell consisting of three absorbers and two RF cavities inside the field of two focus coil magnets. The emittance of the beam is measured before and after the cooling channel using a scintillating fibre tracker inside a superconducting solenoid, and the muons are identified using time-of-flight detectors, a Cherenkov detector and a calorimeter system consisting of a scintillating fibre-lead pre-shower detector (named the KL) and a totally active scintillating detector, called the Electron Muon Ranger (EMR). In this proposal we aim to perform measurements of emittance reduction, without RF cavities (MICE step IV) and perform the final demonstration of ionisation cooling with RF cavities. This proposal is a bid for 9 months funding from April to December 2016 in order to bridge the current MICE Step IV construction grant that ends in March 2016 and the final demonstration of ionisation cooling, expected to run until 2019.