Neutrinos are one of the most enigmatic particles in the standard model. The main reason is that they’re so hard to detect. Despite the fact that 400 trillion of them created in the Sun are passing through a person’s body every second, they rarely interact with normal matter, making understanding anything about them difficult. To help solve their mysteries, a new neutrino detector in China recently started collecting data, and hopes to provide insight on between forty and sixty neutrinos a day for the next ten years.
The detector, known as the Jiangmen Underground Neutrino Observatory, or JUNO, is located in between two huge nuclear plants at Yangjian and Taishan. Both of those fission plants create their own artificial neutrinos in addition to the ones created by the Sun, meaning the general area should be awash with barely interacting particles.
That’s despite the fact that, like most neutrino detectors, it’s located underground. 700 meters underground in fact. The physical bulk of the Earth’s crust is meant to block most other particles, like muons, from getting to it, and at other installations, like IceCube, it does a pretty good job.
The inside of the sphere with the scintillating liquid. Credit – JUNO Collaboration
Even so, the detector itself is covered by an additional detector called the “Top Tracker”, which is covering a 44m diameter pool of ultrapure water. Its job is to detect any stray particle that might make it all the way down to the detector. Ultimately it can’t stop them, but it can eliminate the data artifact they might create.
That data artifact would happen if one of the particles hits the “liquid scintillator” inside a sphere surrounded by 43,212 sensitive photodetectors that can pick up individual photons.Combining data from all of the different photodetectors would allow researchers to tease out some of the physical properties of neutrinos, including what, if any, differences there are between the three “types”.
Those are the electron, the muon, and the tau neutrino. Each has slightly different characteristics from one another, and they have the ability to shift between the different types, or “oscillate” in the language of particle physicists. One of the main goals of JUNO is to understand the mass of each, but, given that ask is probably too much, researchers are at least hoping to get a sense of the hierarchy of masses – i.e. which one is heaviest vs lightest. Another potential discovery is how often the types change from one to another – i.e. what is the frequency of their oscillation.
The Top Tracker covering the pool of water surrounding the detector. Credit – JUNO Collaboration
Understanding how neutrinos work would unlock a clearer picture of cosmology, where they are thought to be responsible for the early expansion during the big bang, astrophysics, since they are thought to provide insights into supernovae, and even geology, as radioactive rocks from deep within the Earth emit them. That’s part of the reason scientists have invested so much time and energy into tracking down their properties.
JUNO is the next step in that journey. The setup itself is a collaboration of 74 institutes and 700 individuals, and is led by the Chinese Academy of Science’s Institute for High Energy Physics. It should operate for at least ten years and hopes to collect enough data over that time frame to shed some additional light on the characteristics of these enigmatic particles. If it does, then multiple realms of science will be better for it.
Learn More:
CNRS – JUNO: a giant detector to unravel the mysteries of neutrinos
UT – An Unfinished Detector has Already Spotted the Highest-Energy Neutrino Ever Seen
UT – Catching Ghost Particles in Real Time
UT – IceCube Just Spent 10 Years Searching for Dark Matter