A 1000km3 Ultra-High Energy Neutrino Acoustic Detector

1000km3超高能中微子声探测器

• 批准号: 0457273
• 负责人: Giorgio Gratta
• 金额: --
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0457273&HistoricalAwards=false
• 关键词: 1000km3; Ultra; Energy; Neutrino; Acoustic

In recent years scientists have expanded the horizon of astronomy by observing the Universe first with photons of increasingly smaller wavelengths and then by resorting to particles other than photons. The latest additions to our toolkit are neutrinos, neutral particles with a tiny mass, more than 500,000 times lighter than electrons. While the small mass of neutrinos make them already rather "exotic", it is now possible that ultra-high-energy neutrinos raining down to Earth from the outer space will help us understanding some catastrophic events in the universe. We do know that particles (possibly protons) of kinetic energies 1018 eV and above do occur in cosmic radiation and, in fact, some scientists claim to have observed cosmic rays with energies above 1020 eV. This is a tremendous energy for a single elementary particle, equivalent to the kinetic energy of a medium-sized book falling to the floor from a desk! As a comparison our most powerful particle accelerator can only accelerate protons to 1012 eV. We do not fully understand what kind of process can produce such high energy particles but, if also neutrinos of such high energies were to be produced we would have an important clue. The signals from such energetic particles would be dramatic enough to be recorded in conventional particle detector however the rate at which such energetic neutrinos would rain on Earth is expected to be so low that thousands of cubic kilometers of active material would be needed to have the chance of detecting some. A suitable detector cannot be built with nuts and bolts but it has to take advantage of an existing body of material! Ocean water is very common on the Earth surface and our group, with NSF support, is installing a system that will demonstrate the possibility of detecting ultra-high-energy neutrinos in cosmic radiation by the acoustic noise they are expected to produce when they interact and stop in sea water. Indeed their tremendous kinetic energy is expected to be converted into heat that would make the sea-water expand, producing a peculiar sound. The sound will be detected, in our initial study, by an array of hydrophones (underwater microphones) located off the coast of Florida and used by the US Navy for naval exercises. We have an agreement with the Navy that will allow us to install a special data acquisition system that will allow us to find the tiny pulses characteristic of the neutrino interaction in the large sea background caused by human activities and different sort of marine creatures. This project was initiated almost exclusively with undergraduate students. The initial feasibility study was done by Stanford Undergraduate Shaffique Adam, now at Cornell. The first data taking at the Navy array and the relative data analysis was performed by Stanford undergraduate Justin Vandenbroucke who is now working on the NSF Amanda/Ice Cube detectors in Antarctica as a Berkeley graduate student. A Stanford graduate student, Naoko Kurahashi, is leading the installation of the present system, while another Stanford undergraduate, Jason Kerwin, is building parts of a calibration device that we hope to use in the study.

近年来，科学家首先观察到宇宙的光子越来越小，然后通过诉诸于光子以外的颗粒来扩展天文学的视野。 我们工具包的最新添加是中微子，中性颗粒的质量很小，比电子轻的500,000倍以上。 虽然少量的中微子使它们已经变得“异国情调”，但现在有可能超高能量中微子从外太空下雨将有助于我们理解宇宙中的一些灾难性事件。 我们确实知道，动能的颗粒（可能是质子）1018 eV及以上确实发生在宇宙辐射中，实际上，一些科学家声称观察到宇宙射线，其能量以上的能量超过1020 eV。 对于单个基本粒子来说，这是一种巨大的能量，相当于中型书的动能，从桌子上掉到了地板上！ 作为比较，我们最强大的粒子加速器只能将质子加速至1012 eV。 我们不完全了解哪种过程可以产生如此高的能量颗粒，但是，如果要产生如此高能量的中微子，我们将有一个重要的线索。 来自这种能量颗粒的信号将足够引人注目，可以记录在常规粒子探测器中，但是，这种能量性中微子会在地球上下雨的速度如此之低，以至于需要数千立方教公里的活性材料才能有机会检测一些。 合适的探测器不能用坚果和螺栓构建，但必须利用现有的材料！ 海水在地球表面非常普遍，我们的小组在NSF支持的情况下正在安装一个系统，该系统将证明有可能通过预期在相互作用并停在海水中产生的声学噪声来检测宇宙辐射中超高能量中微子。 确实，他们的巨大动能有望转化为热量，这会使海水扩展，从而产生特殊的声音。 在我们的初步研究中，将通过位于佛罗里达海岸的一系列言语（水下麦克风）检测到声音，并被美国海军用于海军锻炼。 我们与海军达成了一项协议，这将使我们能够安装一个特殊的数据采集系统，这将使我们能够在人类活动和不同种类的海洋生物引起的大海景中找到中微子相互作用的微小脉冲特征。 该项目几乎是由本科生启动的。 最初的可行性研究是由斯坦福大学本科生Shaffique Adam进行的。 斯坦福大学本科生贾斯汀·范登布鲁克（Justin Vandenbroucke）在海军阵列中获取的第一个数据和相对数据分析，他现在正在南极洲的NSF Amanda/Ice Cube探测器工作，他是伯克利的研究生。 斯坦福大学的一名研究生Naoko Kurahashi正在领导当前系统的安装，而斯坦福大学的另一位本科生Jason Kerwin正在建造我们希望在研究中使用的校准设备的一部分。