admin
It’s like sampling the water drops blasting from a fire hose by sticking an eyedropper into the stream. What better way to capture neutrinos is there than plucking them from a concentrated fountain of the particles?
Sampling neutrinos in Switzerland
Detecting them is hard enough but sampling neutrinos for study is a whole magnitude of difficulty harder. Until now, the concept was virtually impossible.
A crew of nuclear physicists in Switzerland at CERN’s Large Hadron Collider proudly announced “the facility’s first detection of neutrinos.” That’s a big deal because it wasn’t built for that. Neutrinos are “some of the smallest, most weakly interacting particles yet proven to exist.” They drive physicists nuts.
The ordinary way scientists study neutrinos is by trapping them. To build a detector they usually start by filling a swimming pool full of dry cleaning fluid, at the bottom of a deep, dark salt mine. Then, they equip it with a fancy array of sensitive instruments to detect flashes of light from a rare collision between one of the elusive particles and the matter in the detector.
Flashes don’t happen often. Being able to snag a neutrino for sampling isn’t possible with that set up. As reported by team member David Casper, “We will detect the highest-energy neutrinos that have ever been produced from a human-made source.”
Trillions of neutrinos pass through your body every second. “Prior to this project, no sign of neutrinos has ever been seen at a particle collider,” study co-author Jonathan Feng declares. The physicist likes to hang out at the University of California-Irvine.
He’s co-leader of the collaboration that managed the experiment. According to the press release, this “significant breakthrough is a step toward developing a deeper understanding of these elusive particles and the role they play in the universe.” Sampling them is the next step.
Meet FASER
The stunning neutrino detection happened during “a pilot run of an emulsion detector called FASER.” The Large Hadron Collider particle physics experiment uses emulsion detectors “for super-small particles, like the unknown stuff that constitutes dark matter.”
They noticed something which surprised them. “It turns out that the most energetic neutrinos are produced along the beamline,” Feng observes. They caught a few for sampling.
“These neutrinos are the most likely to interact, and so by placing FASER along the beamline, we were able to catch a few of them, even though FASER is a very small detector.” The neutrino sampling detector “was made of alternating lead and tungsten plates (101 and 120 of them, respectively), each containing a corresponding number of emulsion films.”
Those are old school photo films like the ones cartridge cameras used. “Neutrinos produced by the reactions in the Large Hadron Collider smash into the heavy metal nuclei in FASER, leaving marks of their presence on the emulsion layers.”
Dr. Feng is “definitely optimistic” for the future of the experiment. FASER’s success, he notes, shows his team is on the right track. “In many scientific areas, the first experiment detects a few particles, a second experiment detects a few more, and a third detects enough to do precise measurements.”
His sampling project is moving forward at light speed. “What this result means is that we expect to pass through all three stages in rapid succession in the next few years. By 2024, we should have detected 10,000 neutrinos at the LHC, and it will be exciting to see what they tell us.”
