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

冰立方中微子天文台（ICNO）深埋在南极冰盖中，是世界上唯一、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。冰立方观测到的大多数中微子的能量都在大气中微子的预期范围内，这些中微子是由来自银河系附近部分的宇宙射线在广泛的空气阵雨中产生的基本粒子的衰变产生的。虽然这些可以用来测量中微子的基本特性，但更高能量的天体物理学中微子是宇宙中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，不会被星系或星系外的磁场偏转，并且可以不受阻碍地穿越充满光子的宇宙。因此，中微子提供了关于强大的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、活动星系核和其他极端的河外现象。该合同将资助在冰立方底部中心的深而清澈的南极冰中部署7个额外的光子传感器串，形成冰立方Gen2第一阶段扩展（“第一阶段”）。深冰钻的可用性为加强现有的冰立方基础设施的研究和教育提供了几个机会。深冰钻也将允许在美国阿蒙森-斯科特南极站现有的冰立方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、生产和现场部署中培训新的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。新串将使用多pmt数字光模块（mdom），提供更好的方向性，每个模块的光电阴极面积增加一倍以上，单位面积成本低于传统的冰立方dom。mdom将紧密集成到现有的IceCube数据采集框架中，只需要增加少量的长期维护和运营费用。新的仪器将极大地提高IceCube在5 GeV能量尺度上的性能，产生比现有样品多一个数量级的统计数据，并使IceCube能够执行世界上最好的tau中微子外观测量和世界上最严格的PMNS （pontecorvoi - maki - nakagawa - sakata）矩阵tau部分的一致性测试。这个矩阵描述了所有已知的中微子振荡行为，偏离一致性将成为新物理学的证据。这些弦将配备新的校准设备，可以更好地模拟冰的光学特性，减少tau中微子外观测量中的系统不确定性，并通过改进用于搜索点源的高能级联事件的方向重建和增强pev尺度tau中微子的识别，增强冰立方对多信道天体物理学的强大贡献。高能tau中微子本质上是天体物理起源的保证，它们是超长基线上中微子振荡物理的独特探测，为第一阶段的低能大气tau中微子外观测量提供了强大的补充。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.