Epoch-making discovery at Cern in Geneva: for the first time scientists were able to observe the interaction of neutrinos, the most "elusive" particles in the universe
The Large Hadron Collider (LHC) is the largest and most powerful particle accelerator in the world: to the LHC we owe, among other things, the momentous discovery of the Higgs Boson, the so-called God particle detected at Cern in Geneva in 2012. Today, scientists involved in the analysis of particle acceleration are at a turning point that could be equally epochal: for the first time in history have been detected interactions between neutrinos.
The first traces of neutrinos
The study, published in the journal Physical Review D, shows the results of observations conducted over the past three years within the scientific program of the Large Hadron Collider. In fact, the FASER (Forward Search Experiment) experiment, led by the University of California, began in 2018: its purpose is to search for new ultralight particles and to analyze the interaction of neutrinos "in acceleration".
Among the subatomic particles, the neutrino is particularly complex to study, since its electric charge is zero, so its possibilities of interaction with the rest of matter are really limited.
In particle physics it is said that to capture half of the neutrinos passing through matter would require an improbable "light-year thick wall of lead": the experiment that took place in the last three years at Cern used the particle accelerator, but it actually also involved the use of layers of lead and tungsten and a nuclear emulsion.
The 27 kilometers of superconducting magnets that make up the ring of the LHC are able to make subatomic particles travel at speeds close to those of light, allowing the effects of collisions between atoms to be observed. Among these effects, there is the possibility that ultra-light particles emerge from the collisions, which can then be studied - often for the first time.
This happened with the Higgs Boson and is happening today with the neutrino, the elementary particle less known and more complex to investigate, which has been observed for the first time.
The Faser experiment
During the collisions produced inside Cern's particle accelerator, some of the neutrinos produced by the collisions collide with the nuclei of metals in the nuclear emulsion detector that is at the center of the experiment.
It is thanks to a "wall of lead," in fact, that the neutrinos become visible: thus generated by the collision with the nuclei of lead and tungsten, the journey of neutrinos within the layers of nuclear emulsion has left traces, giving scientists for the first time the opportunity to observe it.
Six neutrino interactions were observed over the course of the experiment: this is not only a major breakthrough that will allow us to better understand the nature of the universe, but also demonstrates the effectiveness of the instruments tested for the FASER experiment. "This significant breakthrough," says Jonathan Feng, co-author of the study, "is a step toward developing a deeper understanding of these elusive particles and the role they play in the universe."
Before the FASER project, in fact, no sign of neutrinos had ever been detected inside a particle collider. We are therefore just at the beginning of a new course with regard to the knowledge of elementary particles that make up our universe.
From 2022, in fact, is expected to activate FASERĪ½, a new detector of nuclear emulsions much larger and more sensitive than the one that led to the important discovery and that, according to scientists, will be able to "record more than 10,000 interactions of neutrinos" already from the next experiment.