CERN detected its first neutrinos in the LHC

Detecting neutrinos is particularly difficult, especially in a particle accelerator like the LHC. However, CERN researchers succeeded in this, paving the way to new scientific horizons.

Neutrinos are elementary particles that have several remarkable characteristics. We know that they are not only very light, but also electrically neutral and almost inert; they hardly ever interact with the material around them. According to CERN, “Only one in ten billion neutrino crossing the Earth manages to interact with an atom”.

Three particularly handicapping points for research in fundamental physics; because the mass, electric charge and interactions of particles are three of the basic parameters used by researchers to study their behavior. This makes it particularly difficult to track its neutrinos, which has earned them the name of “Ghost particle”. This is quite boring for researchers, because they suspect them of hiding some of the pieces that we still lack to piece together the great puzzle of the universe.

The good news is that neutrinos are extremely abundant. They can come directly from the stars, but also from various and varied phenomena such as supernovas or quasars. They are also produced when cosmic radiation strikes the upper atmosphere, causing a veritable shower of particles. And CERN troops have long considered that they should also be produced within their favorite toy, the Large Hadron Collider (LHC).

When CERN plays Ghostbusters

But despite all the efforts of researchers, this phantom particle still lives up to its name and continues to be discreet since its existence was confirmed in 1956. It takes considerable effort to locate the slightest trace. In France, this is the vocation of Antares. This instrument located 2,500 meters deep in the Mediterranean, off Toulon, uses nine hundred sensors distributed along twelve lines, to examine the passage of neutrinos in the water over an area of ​​10 hectares.

It is therefore very difficult to lay eyes on it, and each observation constitutes a small event in itself. And this is even truer in particle accelerators like the LHC, which constitute the privileged field of exploration in particle physics. But that could change with the new FASERnu instrument, which will enter service next year. In a paper published today, the researchers explained that a prototype compact embedding a proof of concept of this technology allowed them to” observe six interactions of neutrinos. A great first in the context of the LHC.

A decisive proof of concept

Before this project, no trace of neutrino had ever been observed in a particle accelerator”, Insists Jonathan Feng, co-director of the project interviewed by Phys.org. This is good news, which should make researchers particularly optimistic about the promises of FASERnu. This proof of concept has even given them two crucial pieces of information.

Initially, this confirms that the principle of the emulsion detector, on which FASERnu is based, is well and truly capable of detecting neutrino interactions. In principle, this works a bit like the film photography. When a film is exposed to light, the photons leave traces which end up giving the final image after development. The concept is similar within FASERnu; the researchers were able to spot neutrinos by analyzing the traces left on the different materials in their “film”.

Second, this experiment also showed them the precise point on the LHC where they are most likely to detect the collisions they are looking for. This is also very important, because it will later allow to obtain more precise results. Indeed, this experience was only the beginning. Now, the research team is preparing to repeat the experiment with a new instrument, “much larger and significantly more sensitive”According to Feng. They hope to spot “more than 10,000 neutrinos”During their next test, which will start in 2022.

A new era for basic research

But above all, this new instrument will not be satisfied with reinventing the wheel. He also promises to push the discipline to new heights. Because when the observation of these “ghost particles” becomes routine, the researchers hope that it will be sensitive enough to identify the different types (oddly enough, physicists speak of “flavors”) of neutrinos. With a little luck, it will even identify the famous “antineutrinos”.

These observations could be the key to exploring completely new territories in fundamental physics. Enough to potentially clarify the standard model of particle physics, and advance our knowledge of our universe and its history. We therefore give you an appointment in a few years; by then, researchers will have been able to analyze the first results of FASERnu, which will be installed in 2022.

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