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

该提案请求支持美国大学对英国卢瑟福阿普尔顿实验室 (RAL) 进行的 μ 子电离冷却实验 (MICE) 的贡献。中微子研究的最新发现表明，非常强烈的中微子源或“中微子工厂”可能会回答粒子物理学和宇宙学的基本问题。这个未来的大型科学项目可能会设在美国现有的实验室。 MICE 是实现这一目标的重要一步，并将通过确认关键“μ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放射性核的β衰变过程中释放出的无质量中性粒子。当发现它们有两种（后来是三种）类型时，每种类型（基于观察）都被假定为不可变的。然而，最近的实验结果表明，在足够长的距离内，中微子会从一种中微子振荡到另一种中微子。由此可见，中微子具有非零质量。这一发现提出了有关宇宙中物质总量以及物质多于反物质的起源的基本问题，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存在的电荷共轭宇称（CP）破坏。 尽管使用加速器衍生中微子束的中微子振荡研究现已计划或正在进行，但最近的全球研发工作指出中微子工厂，通过存储环中循环的强μ子束的衰变产生新型中微子束，作为中微子振荡和CP破坏研究的理想工具。这种工具的灵敏度将比当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介子-介子对撞机的第一步，具有研究假定的希格斯共振和能量前沿的轻子碰撞的独特潜力。 所需强度的μ子束只能产生到大的相空间中，但经济实惠的现有加速技术需要小的输入光束。这种不匹配可以通过“冷却”μ子束以减小其尺寸来缓解。 这是 MICE 的目标，并组织了国际合作来实现这一目标。这项研究的更广泛影响包括验证适用于各种科学和技术领域的重要新技术，包括粒子物理学和宇宙学；开发下一代仪器仪表；跨学科和国际大学和国家实验室小组（包括加速器和粒子物理学家和工程师）的合作；培训研究生和本科生，包括来自社区学院和代表性不足的少数族裔的学生；通过外展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.