Support for U.S. Consortium on MICE: The International Muon Ionization Cooling Experiment

这项提议要求美国大学支持在英国卢瑟福·阿普尔顿实验室(RAL)进行的Muon电离冷却实验(MICE)。最近在中微子研究方面的发现表明，一个非常强的中微子源，或称“中微子工厂”，可能会回答粒子物理和宇宙学的基本问题。这个未来的大型科学项目可以设在现有的美国实验室。MICE是迈向这一目标的重要一步，它将通过确认关键的“介子冷却”技术的可行性和性能来验证中微子工厂的成本估算。中微子最初被认为是在放射性原子核的β衰变过程中释放出来的无质量中性粒子。当发现它们有两种(后来是三种)类型时，假设(根据观察)每种类型都是不变的。然而，最近的实验结果表明，在足够长的距离内，中微子会从一种振荡到另一种。由此推论，中微子具有非零质量。这一发现提出了关于宇宙中物质的总量和物质超过反物质的来源的基本问题，并高度重视推断中微子振荡参数的研究，包括中微子混合中可能的电荷共轭宇称(CP)破坏。尽管使用加速器衍生的中微子束进行中微子振荡的研究目前正在计划或正在进行中，但最近全球范围内的研发工作指向一家中微子工厂，它通过在存储环中循环的强µ子束的衰变来产生一种新型的中微子束，作为研究中微子振荡和CP破坏的理想工具。这样的工具将允许灵敏度比目前和计划中的实验高出几个数量级。从长远来看，中微子工厂也将是迈向Muon-Muon对撞机的第一步，它具有在假设的希格斯共振和能量前沿研究轻子碰撞的独特潜力。所需强度的介子束只能被产生到一个大的相空间，但负担得起的现有加速技术需要一个小的输入束。这种失配可以通过为介子束降温来减小其大小来缓解。这是MICE的目标，已经组织了一个国际合作来实现这一目标。这项研究的更广泛影响包括确认一项重要的新技术可应用于各种科学和技术领域，包括粒子物理和宇宙学；开发下一代仪器；跨学科和国际大学及国家实验室小组的协作，包括加速器和粒子物理学家及工程师；培训研究生和本科生，包括来自社区学院和任职人数偏低的少数群体的学生；以及通过外联活动和公共媒体广泛传播信息。

This proposal requests support for a U.S. university-based contribution to the Muon Ionization Cooling Experiment (MICE) being carried out at the Rutherford Appleton Laboratory (RAL) in the U.K. Recent discoveries in the study of neutrinos suggest that a very intense neutrino source, or "Neutrino Factory," might answer fundamental questions of particle physics and cosmology. This large future scientific project could be sited at an existing U.S. laboratory. MICE is an essential step towards this goal and will validate Neutrino Factory cost estimates by confirming the feasibility and performance of the key "muon cooling" technique. Neutrinos were originally postulated as massless neutral particles emitted during beta decay of radioactive nuclei. When they were found to come in two (and, later, three) types, each type was assumed (based on observation) to be immutable. However, recent experimental results indicate that over sufficiently long distances, neutrinos oscillate from one kind into another. From this, it follows that neutrinos have nonzero masses. This discovery raises fundamental issues regarding the total amount of matter in the universe and the origin of the excess of matter over antimatter, and places a high priority on studies to deduce the parameters of neutrino oscillation, including possible Charge conjugation-Parity (CP) violation in neutrino mixing. Although neutrino-oscillation studies using accelerator-derived neutrino beams are now planned or under way, recent world-wide R&D work points to a Neutrino Factory, producing a novel neutrino beam via decay of an intense muon beam circulating in a storage ring, as the ideal tool for neutrino oscillation and CP-violation studies. Such a tool would permit sensitivity several orders of magnitude beyond that of current and planned experiments. A Neutrino Factory would also be the first step towards muon-muon colliders in the longer term, with unique potential for studies of lepton collisions at the postulated Higgs resonance and the energy frontier. Muon beams at the required intensity can only be produced into a large phase space, but affordable existing acceleration technologies require a small input beam. This mismatch could be alleviated by "cooling" the muon beam to reduce its size. This is the goal of MICE and an international collaboration has been organized to carry it out. Broader impacts of this research include validation of an important new technique applicable in a variety of scientific and technological areas, including particle physics and cosmology; development of next-generation instrumentation; collaboration of interdisciplinary and international university and national-laboratory groups including accelerator and particle physicists and engineers; training of graduate and undergraduate students including those from community colleges and underrepresented minorities; and wide information dissemination via outreach activities and public media.