A team of international researchers has just announced the very first detection of candidate neutrinos created by CERN’s Large Hadron Collider, marking a significant step forward in the field (LHC). A paper published in Physical Review D describes how the researchers observed six interactions in a pilot study that was performed in 2018. The findings were published online in Physical Review D.
Neutrinos are elementary particles that are 100,000 times smaller than an electron and have virtually no mass. They are produced in stars, supernovae, and even quasars, and since they seldom interact with matter, they are difficult to detect and study. It is for this reason that neutrinos are often referred to as “ghost particles.” They are, on the other hand, in plentiful supply. The human body, for example, has billions of them at any one time.
Over the last several years, scientists have created many devices that can capture signs of their movement. These devices, which are ultrasensitive light detectors known as photomultipliers, are immersed in clean water in the majority of cases. This is accomplished by observing and detecting the weak flashes (Cherenkov light) that are produced when a neutrino collides with an elemental atom present inside the water.
IceCube, buried in Antarctic ice at the South Pole station, is the world’s largest neutrino detector to date. They may also be found in Japan and in the bottom of Lake Baikal in Russia, among other places.
The idea that particle accelerators, such as the Large Hadron Collider (LHC), in the border area between France and Switzerland, might both make and detect them has been around for a long time. However, it has always been assumed that the correct equipment was lacking. But it has now been done.
In a preliminary test of a neutrino experiment dubbed FASER, which began in 2018, scientists discovered six neutrinos interacting with one another. “No trace of neutrino activity has ever been discovered in a particle collider prior to this effort,” according to Jonathan Feng, co-author of the study.
This discovery marks a major step forward in our knowledge of these elusive particles and the function they play in the cosmos.
The FASER apparatus, which is located 480 meters downstream from the point where particle collisions occur, is made up of plates of lead and tungsten that are separated by layers of emulsion. In this process, some of the neutrinos will hit the nuclei of atoms in the metal, releasing additional particles that will move through the layers of the metal and leave visible traces in the process.
Taking advantage of this accomplishment, the FASER team, which is comprised of 76 theoretical and experimental physicists from 21 universities in nine countries, is planning a new round of tests using a far bigger and more sensitive apparatus known as FASERnu. When compared to the pilot instrument, the latter will weigh more than 1,090 kg, while the former weighs just 29 kg. Because of its greater sensitivity, it will be able to detect more neutrinos and do so more often.
David Casper, a co-author of the paper, said, “Given the power of our new detector and its unique placement at CERN, we aim to be able to record more than 10,000 neutrino interactions in the next LHC cycle, starting in 2022.” According to the researchers, they will be able to identify the most energetic neutrinos that have ever been created from an artificial source.
At the end of the day, understanding these “ghost particles” may reveal solutions to some of the world’s most difficult physics questions, such as why the Universe is composed only of matter and not of antimatter, among others.