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

埋藏在南极冰盖深处的冰立方中微子天文台(ICNO)是世界上唯一、最大、最灵敏的高能中微子望远镜。它是一个10亿吨重的探测器，使用南极深层冰层作为媒介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扇区的宇宙射线在大范围的气雨中产生的基本粒子的衰变而产生的。虽然这些可以用来测量中微子的基本性质，但更高能量的天体物理中微子是探索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即使是稠密的空间，不会受到银河系或银河系外磁场的偏转，也不会畅通无阻地穿过充满光子的宇宙。因此，中微子提供了关于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、活动星系核和其他极端的河外现象。该合同将资助在IceCube底部中心的深厚、透明的南极冰层中额外部署七组光子传感器，形成IceCube Gen2第一阶段扩展(“第一阶段”)。深冰钻探的提供为加强现有的冰立方研究和教育基础设施提供了几个机会。深冰钻探还将有可能在美国阿蒙森-斯科特南极站现有的IceCube运营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一批新的国际学生和年轻科学家提供新的机会。天体物理学和极地气候的结合吸引了人们的广泛兴趣。新的弦将使用多PMT数字光学模块(MDOM)，提供更好的方向性，每个模块的光电阴极面积是传统冰立方模块的两倍多，单位面积成本更低。MDOM将紧密整合到现有的IceCube数据采集框架中，但增加的长期维护和运营费用微乎其微。新的仪器将极大地提高IceCube在5GeV能量范围内的性能，产生比当前样本多一个数量级的统计数据，并使IceCube能够执行世界上最好的tau中微子外观测量，以及世界上最严格的PMNS(Pontecorvo-Maki-Nakagawa-Sakata)矩阵tau部分的单一性测试。这个矩阵描述了所有已知的中微子振荡行为，偏离一元性将是新物理学的证据。这些弦将配备新的校准设备，可以更好地模拟冰的光学性质，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对PeV级tau中微子的识别，增强IceCube对多传送器天体物理的强大贡献。高能tau中微子本质上保证是天体物理的起源，它们是超长基线上中微子振荡物理的独特探测器，与第一阶段的S大气tau中微子在较低能量下的出现提供了强大的补充。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智力优势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.