How Physicists Track and Trap the Elusive Neutrino
S eventy years ago, the physicists Clyde Cowan and Frederick Reines took a custom-built 10-ton detector, surrounded it with thick lead walls and wet sandbags, and placed it near a powerful nuclear reactor at the Savannah River Plant in South Carolina.
七年前，物理学家克莱德·考恩（Clyde Cowan）和弗雷德里克·雷因斯（Frederick Reines）采用了一个定制的 10 吨重探测器，用厚厚的铅墙和湿沙袋将其包围，并将其放置在南卡罗来纳州萨凡纳河核电站的一个强大核反应堆附近。
They called the experiment “Project Poltergeist,” designed as it was to catch a ghost.
他们将这项实验称为“Project Poltergeist”，旨在捕捉鬼魂。
More than a quarter of a century before, physicists had been puzzling over why energy appeared to be lost during a radioactive process called beta decay.
超过四分之一个世纪之前，物理学家一直在困惑为什么能量会在称为β衰变的放射性过程中损失。
Something was missing, and there was no known physics to explain it.
缺少了一些东西，并且没有已知的物理学可以解释它。
Then in 1930, the Austrian physicist Wolfgang Pauli proposed a radical solution: A virtually undetectable particle was silently carrying the missing energy away.
1930 年，奥地利物理学家沃尔夫冈·泡利 (Wolfgang Pauli) 提出了一个激进的解决方案：一个几乎无法检测到的粒子正在悄悄地带走缺失的能量。
“I have done a terrible thing,” Pauli told a friend.
“我做了一件可怕的事情，”泡利告诉一位朋友。
“I have postulated a particle that cannot be detected.” It would come to be known as the neutrino.
“我假设存在一种无法检测到的粒子。”它后来被称为中微子。
Having almost no mass and no charge, these particles can pass through Earth and everything on it, including our bodies, virtually unimpeded.
这些粒子几乎没有质量和电荷，可以毫无阻碍地穿过地球和地球上的一切，包括我们的身体。
The massive device that Cowan and Reines deployed in early 1956 was meant to find what Pauli thought was impossible.
Cowan 和 Reines 在 1956 年初部署的大型设备旨在发现 Pauli 认为不可能的事情。
That June, the pair of physicists from the Los Alamos National Laboratory sent Pauli a telegram : “We are happy to inform you that we have definitely detected neutrinos.”
那年六月，洛斯阿拉莫斯国家实验室的两位物理学家给泡利发了一封电报：“我们很高兴地通知您，我们确实检测到了中微子。”
Attention then shifted to a broader question.
然后注意力转移到一个更广泛的问题上。
If nuclear reactions produce neutrinos, could we use them to peer at the nuclear fireworks inside stars, including the sun?
如果核反应产生中微子，我们可以用它们来观察恒星（包括太阳）内部的核烟花吗？
This presented a huge challenge: How can you possibly catch particles shooting from distant stars if these particles can pass through almost anything undetected?
这提出了一个巨大的挑战：如果这些粒子可以穿过几乎任何未被发现的物体，你怎么可能捕捉到从遥远恒星射出的粒子？
The suspicion was that detecting a particle that rarely collides with matter requires a vast amount of matter for it to collide with.
人们怀疑，探测很少与物质碰撞的粒子需要大量的物质与之碰撞。
Moreover, the matter would have to be shielded from the noise of other forms of radiation.
此外，该物质必须免受其他形式辐射的噪音影响。
So the answer scientists came up with was to build some of the biggest, deepest, and most exotic experimental traps in scientific history …
因此，科学家们想到的答案是建造一些科学史上最大、最深、最奇特的实验陷阱……
and then wait.
然后等待。
In the 1960s, Raymond Davis Jr. and colleagues at Brookhaven National Laboratory placed a tank 1.5 kilometers underground in the Homestake mine in South Dakota and filled it with nearly 400,000 liters of a chlorine-based cleaning fluid called perchloroethylene.
20 世纪 60 年代，布鲁克海文国家实验室的 Raymond Davis Jr. 和同事在南达科他州 Homestake 矿井地下 1.5 公里处放置了一个储罐，并在其中注入了近 400,000 升名为全氯乙烯的氯基清洁液。
On the rare occasion that a passing neutrino struck a chlorine nucleus, it would be transformed into a radioactive form of argon that could be detected and counted.
在极少数情况下，经过的中微子撞击氯核，它会转化为可以检测和计数的放射性形式的氩。
The experiment, which would run for 25 years, found just one-third the number of neutrinos coming from the sun that had been predicted in theoretical models.
该实验持续了 25 年，发现的来自太阳的中微子数量仅为理论模型预测的三分之一。
This became known as the solar neutrino problem.
这被称为太阳中微子问题。
Decades passed before it was solved — by yet more massive experiments.
几十年后，这个问题才通过更大规模的实验得到解决。
Deep in the Kamioka mine in Japan, Masatoshi Koshiba built a different kind of detector called Kamiokande, which used 3 million liters of ultrapure water.
在日本神冈矿井深处，Masatoshi Koshiba 建造了一种不同类型的探测器，称为 Kamiokande，它使用了 300 万升超纯水。
In this setup, neutrinos occasionally interact with atomic nuclei in the water.
在这种设置中，中微子偶尔会与水中的原子核相互作用。
The interaction creates an electron that moves so fast, it generates a flash of what’s called Cherenkov light.
这种相互作用产生了一个移动速度如此之快的电子，它产生了所谓的切伦科夫光的闪光。
This light gets picked up by detectors.
该光被探测器捕获。
Kamiokande and Koshiba confirmed Davis’ shortfall, and a second, even larger detector, Super-Kamiokande, as well as Canada’s Sudbury Neutrino Observatory, explained the discrepancy.
神冈探测器和小芝证实了戴维斯的不足，而第二个更大的探测器超级神冈探测器以及加拿大萨德伯里中微子天文台则解释了这一差异。
Neutrinos come in three different “flavors” (electron, muon, and tau) and can oscillate, or switch, between them.
中微子有三种不同的“味道”（电子、μ子和τ子），并且可以在它们之间振荡或切换。
To do so, neutrinos must have mass, which the laws of physics failed (and still fail) to predict.
为此，中微子必须具有质量，而物理定律未能（并且仍然未能）预测到这一点。
Newer neutrino detectors continue the tradition of grand ambitions and surprising results.
新型中微子探测器延续了雄心勃勃和令人惊讶的结果的传统。
The IceCube Neutrino Observatory below the Amundsen-Scott South Pole Station uses Antarctic ice instead of water.
阿蒙森-斯科特南极站下方的冰立方中微子观测站使用南极冰代替水。
It has developed a map of the Milky Way made up only of neutrinos and traced these high-energy cosmic particles back to active galaxies powered by supermassive black holes.
它绘制了仅由中微子组成的银河系地图，并将这些高能宇宙粒子追溯到由超大质量黑洞驱动的活跃星系。
On the floor of the Mediterranean Sea, the Cubic Kilometer Neutrino Telescope (KM3NET) has detected the highest-energy cosmic neutrino on record.
在地中海海底，立方公里中微子望远镜（KM3NET）探测到了有记录以来最高能量的宇宙中微子。
Its source remains unknown.
它的来源仍然未知。
Neutrino oscillations, and the myriad mysteries they give rise to, have driven the development of the newest wave of detectors.
中微子振荡及其引发的无数谜团推动了最新一波探测器的发展。
China’s Jiangmen Underground Neutrino Observatory (JUNO) launched in 2025; initial data published in June 2026 provided the most precise measurements of neutrino oscillation reported to date.
中国江门地下中微子观测站（JUNO）将于2025年启动； 2026 年 6 月发布的初始数据提供了迄今为止报道的最精确的中微子振荡测量结果。
Japan’s Hyper-Kamiokande (Hyper-K) and the Deep Underground Neutrino Experiment (DUNE) in the American Midwest are both expected to begin operation later this decade.
日本的超级神冈实验（Hyper-K）和美国中西部的深层地下中微子实验（DUNE）预计将于本十年晚些时候开始运行。
Because of these and other audacious experiments, the particle that Pauli was sure could never be caught has slowly been revealing its secrets.
由于这些和其他大胆的实验，泡利确信永远无法捕获的粒子已经慢慢地揭示了它的秘密。
The recipe for discovery hasn’t changed in seven decades: Think big, go deep, and summon patience.
七十年来，发现的秘诀一直没有改变：大处着眼，深入思考，并保持耐心。
Raymond Davis Jr. is dwarfed by the giant tank used by the Homestake detector in South Dakota, which first detected solar neutrinos.
与南达科他州 Homestake 探测器使用的巨型水箱相比，小雷蒙德·戴维斯 (Raymond Davis Jr.) 显得相形见绌，该探测器首次探测到了太阳中微子。
Creating a large enough trap for neutrinos required a tank one-fifth the volume of an Olympic-size swimming pool filled with chlorine-rich dry-cleaning fluid and buried almost 1.5 kilometers underground.
创建一个足够大的中微子陷阱需要一个容量为奥林匹克标准游泳池五分之一的水箱，里面充满了富含氯的干洗液，并埋在地下近 1.5 公里处。
Brookhaven National Laboratory/Science Photo Library
布鲁克海文国家实验室/科学图片库
The Super-Kamiokande facility in Japan is 12 stories tall and lined with detectors that can sense the flashes of light caused by neutrino interactions.
日本的超级神冈设施有 12 层楼高，排列着探测器，可以感知中微子相互作用引起的闪光。
It’s typically filled with ultrapure water; this image was taken during maintenance.
它通常充满超纯水；这张照片是在维护期间拍摄的。
Drag the image to explore.
拖动图像进行探索。
Kamioka Observatory, ICRR, The University of Tokyo / NHK Enterprises, Inc.
神冈天文台、ICRR、东京大学 / NHK Enterprises, Inc.
Different varieties of neutrinos passing through the Super-Kamiokande detector create telltale patterns on the walls of the detectors.
穿过超级神冈探测器的不同种类的中微子会在探测器壁上形成明显的图案。
Here we see a muon neutrino (top) and an electron neutrino (bottom): two of the fundamental particles in the Standard Model of particle physics.
在这里，我们看到一个μ子中微子（顶部）和一个电子中微子（底部）：粒子物理标准模型中的两个基本粒子。
Different varieties of neutrinos passing through the Super-Kamiokande detector create telltale patterns on the walls of the detectors.
穿过超级神冈探测器的不同种类的中微子会在探测器壁上形成明显的图案。
Here we see the traces of a muon neutrino (left) and an electron neutrino (right): two of the fundamental particles in the Standard Model of particle physics.
在这里，我们看到了μ子中微子（左）和电子中微子（右）的痕迹：粒子物理标准模型中的两种基本粒子。
Super-Kamiokande Collaboration/Science Photo Library
超级神冈协作/科学图片库
Located 2.1 kilometers underground in the Creighton mine in Ontario, Canada, the Sudbury Neutrino Observatory’s detector (top) was filled with “heavy” water, which features deuterium in place of hydrogen atoms.
萨德伯里中微子天文台的探测器（上图）位于加拿大安大略省克雷顿矿井地下 2.1 公里处，里面充满了“重”水，其中的氢原子被氘取代。
Its findings provided evidence that neutrinos can change, or “oscillate,” between different flavors.
它的发现提供了证据表明中微子可以在不同的味道之间变化或“振荡”。
On the bottom is a wide-angle view of the detector’s interior, in the center of which sits a 12-meter-diameter acrylic sphere that holds 1,000 tons of ultra-pure heavy water.
底部是探测器内部的广角视图，探测器的中心是一个直径12米的亚克力球体，可容纳1000吨超纯重水。
Located 2.1 kilometers underground in the Creighton mine in Ontario, Canada, the Sudbury Neutrino Observatory’s detector (left) was filled with “heavy” water, which features deuterium in place of hydrogen atoms.
萨德伯里中微子天文台的探测器（左）位于加拿大安大略省克赖顿矿井地下 2.1 公里处，里面充满了“重”水，其中的氢原子被氘取代。
Its findings provided evidence that neutrinos can change, or “oscillate,” between different flavors.
它的发现提供了证据表明中微子可以在不同的味道之间变化或“振荡”。
On the right is a wide-angle view of the detector’s interior, in the center of which sits a 12-meter-diameter acrylic sphere that holds 1,000 tons of ultra-pure heavy water.
右侧是探测器内部的广角视图，探测器的中心是一个直径12米的亚克力球体，可容纳1000吨超纯重水。
SNO+ succeeded the Sudbury Neutrino Observatory in the Creighton mine and repurposed some of its predecessor’s equipment.
SNO+ 继承了克赖顿矿的萨德伯里中微子观测站，并重新利用了其前身的一些设备。
But instead of heavy water, it was filled with linear alkylbenzene (LAB), which is used commercially to manufacture dish soap.
但它填充的不是重水，而是直链烷基苯（LAB），这种物质在商业上用于制造洗碗皂。
LAB produces signals 50 times brighter than those produced by heavy water.
LAB 产生的信号比重水产生的信号亮 50 倍。
Hanging from the top is the experiment’s director, Art McDonald.
实验负责人阿特·麦克唐纳 (Art McDonald) 悬挂在顶部。
Volker Steger/Science Photo Library
沃尔克·施泰格/科学图片库
The Borexino neutrino detector, buried near Abruzzo, Italy, at the Gran Sasso National Laboratory, provided the first direct evidence that the sun fuses hydrogen into helium in more than one way.
埋藏在意大利阿布鲁佐附近格兰萨索国家实验室的 Borexino 中微子探测器提供了第一个直接证据，证明太阳以多种方式将氢融合成氦。
Above, a researcher checks a photomultiplier tube, which amplifies light created by neutrino interactions.
上图中，研究人员检查了光电倍增管，该管放大中微子相互作用产生的光。
Volker Steger/Science Photo Library
沃尔克·施泰格/科学图片库
These basketball-size digital optical modules (DOM) are the primary sensors used by the IceCube Neutrino Observatory at the South Pole.
这些篮球大小的数字光学模块 (DOM) 是南极冰立方中微子观测站使用的主要传感器。
Scientists threaded more than 5,000 DOMs onto cables like pearls on a necklace, then used jets of hot water to bury them up to 2.5 kilometers deep under Antarctic ice.
科学家们将 5000 多个 DOM 串在电缆上，就像项链上的珍珠一样，然后使用热水喷射将它们埋在南极冰层下 2.5 公里深的地方。
Here, ice serves the role that liquid does inside other detectors — a neutrino collision creates a fast-moving electron, and the subsequent flash gets picked up by the DOMs.
在这里，冰起到了液体在其他探测器内的作用——中微子碰撞产生快速移动的电子，随后的闪光被 DOM 接收。
Jim Haugen, IceCube/NSF (left); Mark Krasberg, IceCube/NSF
Jim Haugen，IceCube/NSF（左）；马克·克拉斯伯格，IceCube/NSF
This data visualization shows a neutrino rippling across the buried strings of DOMs in the IceCube Neutrino Observatory.
该数据可视化显示了冰立方中微子天文台中埋藏的 DOM 串中的中微子的涟漪。
The event, from 2010, corresponds to a high-energy neutrino generated by sources within the Milky Way.
该事件发生于 2010 年，对应于银河系内源产生的高能中微子。
The size of each sphere corresponds to the brightness of the signal detected by each DOM, and the colors indicate arrival time — red first and blue last.
每个球体的大小对应于每个 DOM 检测到的信号的亮度，颜色表示到达时间 - 首先是红色，最后是蓝色。
Workers deploy digital optical monitors for the underwater KM3NET neutrino detector, which is still under construction.
工作人员正在为仍在建造中的水下 KM3NET 中微子探测器部署数字光学监视器。
Nearly 200,000 optical sensors will be anchored to the floor of the Mediterranean Sea at a depth of around 3,500 meters off the coast of Sicily, as well as in a second, smaller array near Toulon, France.
近 200,000 个光学传感器将固定在西西里岛海岸约 3,500 米深处的地中海海底，以及法国土伦附近的第二个较小的阵列中。
The sensors will detect the Cherenkov light generated by secondary particles produced by neutrino interactions with the surrounding water or rock.
传感器将检测中微子与周围水或岩石相互作用产生的二次粒子产生的切伦科夫光。
China’s Jiangmen Underground Neutrino Observatory (JUNO), seen here under construction in 2023, is currently the world’s largest neutrino detector.
图中所示的中国江门地下中微子观测站 (JUNO) 于 2023 年正在建设中，是目前世界上最大的中微子探测器。
It began collecting data in August 2025; one of its main goals is to determine the outstanding mystery of how heavy each flavor of neutrino is.
它于 2025 年 8 月开始收集数据；它的主要目标之一是确定每种中微子的重量这一未解之谜。
The Deep Underground Neutrino Experiment (DUNE) will generate trillions of neutrinos and send them 1,300 kilometers through the earth to study them when they interact with two detectors — a “near” one 60 meters underground at the Fermi National Accelerator Laboratory, and a “far” one 1.5 kilometers beneath the surface at Sanford Underground Research Facility in Lead, South Dakota (top).
深层地下中微子实验 (DUNE) 将产生数万亿中微子，并在它们与两个探测器相互作用时将它们发送到地球 1,300 公里外进行研究。“近”探测器位于费米国家加速器实验室地下 60 米处，“远”探测器位于南达科他州利德市桑福德地下研究设施地表以下 1.5 公里处（上）。
Smaller-scale prototypes of the detectors (bottom), called ProtoDUNE, are being tested at CERN, the particle physics lab on the border of Switzerland and France.
较小规模的探测器原型（下）被称为 ProtoDUNE，正在欧洲核子研究中心（位于瑞士和法国边境的粒子物理实验室）进行测试。
The Deep Underground Neutrino Experiment (DUNE) will generate trillions of neutrinos and send them 1,300 kilometers through the Earth to study them when they interact with two detectors — a “near” one 60 meters underground at the Fermi National Accelerator Laboratory, and a “far” one 1.5 kilometers beneath the surface at Sanford Underground Research Facility in Lead, South Dakota (left).
深层地下中微子实验 (DUNE) 将产生数万亿中微子，并在它们与两个探测器相互作用时将它们发送到地球 1,300 公里外进行研究。“近”探测器位于费米国家加速器实验室地下 60 米处，“远”探测器位于南达科他州利德市桑福德地下研究设施地表以下 1.5 公里处（左）。
Smaller-scale prototypes of the detectors (right), called ProtoDUNE, are being tested at CERN, the particle physics lab on the border of Switzerland and France.
较小规模的探测器原型（右）称为 ProtoDUNE，正在欧洲核子研究中心（位于瑞士和法国边境的粒子物理实验室）进行测试。
Matthew Kapust, Sanford Underground Research Facility (left); Maximilien Brice/CERN
马修·卡普斯特 (Matthew Kapust)，桑福德地下研究设施（左）；马克西米连·布莱斯/欧洲核子研究中心
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《Quanta》杂志对评论进行审核，以促进知情、实质性、文明的对话。
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辱骂、亵渎、自我推销、误导、语无伦次或偏离主题的评论将被拒绝。
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