Physicists from the University of California, Irvine (UCI) found never-before-seen "ghost particles", or neutrinos, in the Large Hadron Collider (LHC) during an experiment called FASER, a report from New Atlas reveals.
Neutrinos are electrically neutral elementary particles with a mass close to zero. The reason they're known as ghost particles is that, though they are incredibly common, they have no electric charge, meaning they are difficult to detect as they rarely interact with matter.
'Ghost particles' could carry immense amounts of information
Alongside the FASER experiments at the LHC, a series of in-development neutrino observatories, designed to detect neutrino sources in space, have the potential to reveal many of the universe's mysteries. Despite their name, ghost particles might actually provide a wealth of information due to the fact that they don't interact with other matter as they travel through the universe — unlike light particles, photons, which are distorted by interactions as they traverse space. The problem, so far, has been our ability to detect these ghost particles or neutrinos.
Neutrinos are produced in stars, supernovae, and quasars, as well as in human-made sources. It has long been believed, for example, that particle accelerators such as LHC should also produce them, though they have likely gone undetected. Now, a paper published in the journal Physical Review D, provides the first evidence of neutrinos, in the form of six neutrino interactions, at the LHC.
"Prior to this project, no sign of neutrinos has ever been seen at a particle collider," study co-author Jonathan Feng said in a press statement. "This significant breakthrough is a step toward developing a deeper understanding of these elusive particles and the role they play in the universe."
The FASER experiment will be expanded by 2022
Back in 2018, the FASER experiment installed an instrument to detect neutrinos, some 1,575 ft (480 m) down from where particle collisions occur in the LHC. The instrument uses a detector composed of plates of lead and tungsten, which are set apart by layers of emulsion. When neutrinos smash into nuclei in the metals, they produce particles that then travel through the layers of emulsion. This creates marks that are visible following a processing procedure that's somewhat similar to film photography. During the experiments, six of these marks were spotted after processing.
According to Feng, the team is "now preparing a new series of experiments with a full instrument that's much larger and significantly more sensitive," so as to collect more data. This larger version will be called FASERnu. It will weigh 2,400 lb (1,090 kg) — a lot more than the first version's 64 lb (29 kg) — allowing it to detect many more of the elusive ghost particles. David Casper, another co-author of the study, says the UCI team expects FASERnu to "record more than 10,000 neutrino interactions in the next run of the LHC, beginning in 2022."