For the first time, physicists have discovered “ghost particles” in the Large Hadron Collider. FASER, a particle collision experiment, picked up telltale evidence of neutrinos being created, which can help scientists better grasp crucial physics.
Neutrinos are electrically neutral elementary particles that are exceedingly light and rarely interact with matter particles. Even while neutrinos are extremely numerous – billions of them are currently rushing through your body – this makes them difficult to detect. As a result, they’re frequently referred to as “ghost particles.”
Stars, supernovae, quasars, radioactive decay, and cosmic rays interacting with atoms in the Earth’s atmosphere all produce neutrinos. It’s long been assumed that particle accelerators, such as the LHC, should produce them as well, but without the correct sensors, they’d simply whiz away undetected.
The “correct instrument” has now been installed and tested. Six neutrino interactions were detected during a pilot run of the FASER experiment, which was deployed in 2018.
“No indication of neutrinos had ever been seen at a particle collider before this effort,” says Jonathan Feng, co-author of a paper explaining the findings. “This remarkable achievement is a step toward a better understanding of these enigmatic particles and their role in the universe.”
The FASER equipment, which is located 480 metres (1,575 feet) away from the particle collisions, functions similarly to film photography, according to the researchers. The detector is made up of lead and tungsten plates separated by emulsion layers. Some neutrinos will collide with the nuclei of atoms in dense metals, resulting in the creation of additional particles that will flow through the emulsion. When the emulsion layers are “developed” like film, the tracks they leave behind can be observed. Six of these markers were found in the data, as expected.
The FASER team is currently developing a new series of tests with a full device that is much larger and significantly more sensitive, after confirming the effectiveness of the emulsion detector strategy for studying the interactions of neutrinos produced at a particle collider,” explains Feng.
FASERnu, the full version, will weigh more than 1,090 kg (2,400 lb), compared to the pilot’s 29 kg (64 lb). Its increased sensitivity will allow it to detect neutrinos more frequently, as well as distinguish between the three “flavours” they come in, as well as antineutrinos.
We hope to be able to record more than 10,000 neutrino interactions in the next run of the LHC, which begins in 2022, thanks to the power of our new detector and its prime location at CERN,” says David Casper, co-author of the paper. “We will detect the highest-energy neutrinos ever created by a human-made source,” says the team.