IceCube Upgrade: An IceCube Extension for Precision Neutrino Physics and Astrophysics

冰立方中微子观测站 (ICNO) 嵌入南极冰盖深处，是世界上独特、最大、最灵敏的高能中微子望远镜。它是一个十亿吨的探测器，利用南极深处的冰作为介质来探测高能大气和天体物理中微子。 IceCube观测到的大多数中微子的能量范围都在大气中微子的预期范围内，这些中微子源自来自银河系附近扇区的宇宙射线在广泛的空气簇射中产生的基本粒子的衰变。虽然这些可用于测量中微子的基本特性，但较高能量的天体物理中微子是宇宙高能现象的关键探测器。由于其独特的性质，中微子几乎可以自由地穿过密集的空间，并且不会受到银河系或银河系外磁场的偏转，并且可以不受阻碍地穿越充满光子的宇宙。因此，中微子提供了有关强大宇宙物体的动力学和内部的直接信息，这些物体可能是高能宇宙射线的起源：超新星、黑洞、脉冲星、活跃星系核和其他极端河外现象。该奖项将资助在 IceCube 底部中心深处、清澈的南极冰层中部署另外七串光子传感器，形成 IceCube Gen2 第一阶段扩展（“第一阶段”）。 深冰钻机的出现为增强现有研究和教育冰立方基础设施提供了多种机会。 深冰钻探还将允许在美国阿蒙森-斯科特南极站现有的IceCube操作框架内部署下一代光学传感器技术原型，为在仪器开发、生产和现场部署过程中培训新一批国际学生和年轻科学家提供新的机会。 天体物理学和极端极地气候的结合引起了广泛的兴趣。新的串将使用多 PMT 数字光学模块 (mDOM)，与传统的 IceCube DOM 相比，它提供更好的方向性和每个模块两倍以上的光电阴极面积，单位面积成本更低。 mDOM 将紧密集成到现有的 IceCube 数据采集框架中，但会增加少量的长期维护和运营费用。新仪器将极大地提升 IceCube 在 5 GeV 能量尺度上的性能，产生比当前样本多一个数量级的统计数据，并使 IceCube 能够对 tau 中微子外观进行世界上最好的测量，并对 PMNS（Pontecorvo-Maki-Nakakawa-Sakata）矩阵的 tau 扇区进行世界上最严格的幺正性测试。 该矩阵描述了所有已知的中微子振荡行为，而与幺正性的偏差将成为新物理学的证据。 这些弦将配备新的校准装置，可以更好地模拟冰的光学特性，减少 tau 中微子外观测量的系统不确定性，并通过改进高能级联事件方向的重建以搜索点源和增强对 PeV 尺度 tau 中微子的识别，增强 IceCube 对多信使天体物理学的强大贡献。高能 tau 中微子本质上保证是天体物理起源，它们是超长基线中微子振荡物理的独特探测器，与第一阶段的低能大气 tau 中微子外观测量提供了强大的互补性。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Embedded deep in the ice cap at the South Pole, the IceCube Neutrino Observatory (ICNO) is the world's unique, largest, and most sensitive high energy neutrino telescope. It is a one-billion-ton detector that uses the deep Antarctic ice as a medium to detect high energy atmospheric and astrophysical neutrinos. Most of the neutrinos observed by IceCube exhibit energies in the range expected for atmospheric neutrinos that originate from decays of elementary particles produced in extensive air showers by cosmic rays coming from nearby sectors of the Milky Way Galaxy. While these can be used to measure the fundamental properties of neutrinos, astrophysical neutrinos at higher energies are key probes of the high-energy phenomena in the Universe. Because of their unique properties, neutrinos pass almost freely through even dense volumes of space and are not deflected by galactic or extra-galactic magnetic fields and traverse the photon-filled universe unhindered. Thus, neutrinos provide direct information about the dynamics and interiors of the powerful cosmic objects that may be the origins of high energy cosmic rays: supernovae, black holes, pulsars, active galactic nuclei and other extreme extragalactic phenomena. This award will fund the deployment of seven additional strings of photon sensors in the deep, clear Antarctic ice at the bottom center of IceCube, forming the IceCube Gen2 Phase 1 extension ("Phase 1"). The availability of a deep-ice drill presents several opportunities to enhance the existing IceCube infrastructure for research and education. Deep ice drills will also allow for the possibility of deploying next-generation optical sensor technology prototypes within the existing IceCube operations framework at the U.S. Amundsen-Scott South Pole Station, presenting new opportunities for training a new cohort of international students and young scientists throughout the instrumentation development, production, and field deployment. The combination of astrophysics and the extreme polar climate attracts wide popular interest.The new strings will use multi-PMT Digital Optical Modules (mDOMs), providing better directionality and more than double the photocathode area per module, at lower cost per unit area, than traditional IceCube DOMs. The mDOMs will be tightly integrated into the existing IceCube data acquisition framework, at marginal added long-term maintenance and operations expense. The new instrumentation will dramatically boost IceCube's performance at the 5 GeV energy scale, yielding over an order of magnitude more statistics than current samples, and enabling IceCube to perform the world's best measurement of tau neutrino appearance and the world's most stringent test of unitarity in the tau sector of the PMNS (Pontecorvo-Maki-Nakagawa-Sakata) matrix. This matrix describes all known neutrino oscillation behavior, and deviations from unitarity would be evidence for new physics. The strings will feature new calibration devices that would allow to better model the optical properties of the ice, reducing systematic uncertainties in the tau neutrino appearance measurement and enhancing IceCube's already strong contribution to multimessenger astrophysics via improved reconstruction of the direction of high energy cascade events for searches of point sources and enhanced identification of PeV-scale tau neutrinos. High energy tau neutrinos are essentially guaranteed to be astrophysical in origin, and they are a unique probe of neutrino oscillation physics over ultra-long baselines, providing powerful complementarity with Phase 1's atmospheric tau neutrino appearance measurement at lower energies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.