The study confirms that the proton has an intrinsic charm quark

While physicists have been debating this for nearly four decades, new data analysis by the NNPDF collaboration reveals that the proton actually contains another fundamental particle called a charm quark. The intrinsic nature of this quark may have important implications in the search for new physics.

All matter around us is made up of atoms, which are made up of subatomic particles: protons and Neutrons Create a center and gravitate around it Electrons. According to the standard model of particle physics, the proton is called a composite particle: experimental evidence shows that it is made up of at least three particles (two quarks). up to and a quark under), bound by gluons. However, quantum theory predicts that the proton may contain many quark-antiquark pairs, including quarks. Charm – These are heavier than protons.

Theorists believe that these quarks Charm “Intrinsic” to the proton, meaning they are part of the proton on long timescales and are not the result of interactions with an external particle. However, no experiment has succeeded in proving the existence of this quark. Charm Inherent at this time. Thanks to the analysis of large volumes of collision data through machine learning techniques, the NNPDF collaboration finally provides the long-awaited proof.

Data from over 500,000 collisions were analyzed

NNPDF collaboration (For this Neural network Barton distribution function) conducts research in the field of high energy physics. The aim is to determine the precise structure of the proton (i.e. the distribution of its constituents, quarks and gluons) using the methods.Artificial intelligence. This knowledge is an important part of the Large Collider’s research program Hadrons (LHC) at CERN.

Specifically, the team used a machine learning model to generate different hypothetical structures of protons, with different flavors of quarks; Remember that these flavors are six in number: up to, under, top, below, Different And Charm. They compared these different proton structures with results obtained during more than 500,000 real collisions carried out in particle accelerators over the past ten years.

They found that a small fraction (0.5%) of the proton’s momentum is attributed to a quark. Charm. The latter are much heavier than quarks up to And under (A few thousand times heavier than a quark up to !). This finding is particularly concerning An LHCb experiment (Large Hadron Collider beauty) was carried out last year on the Z boson, which revealed the existence of quarks Charm in protons. According to their calculations, the team estimates that the protons — which are a little less than 1 GeV — are made up of quarks. Charm and their antiparticle, each with a mass of about 1.5 GeV, sometimes appear arbitrary.

The level of confidence is still low

So, incredible as it may seem, the proton is a particle larger than itself! ” It goes against all common sense. If you buy one kg of salt packet, you will get two kg of sand. But in quantum mechanics, it is very possible. », Juan Rojo explainstheoretical physicist at the Free University of Amsterdam and lead author of the paper describing the discovery.

The researchers also say that if the proton did not have a pair of charm-anticharm quarks, there would be only a 0.3% chance of obtaining the experimentally observed values. This gives their results a confidence level of 3 sigma. ” This is what we call the serious index in particle physics “Rojo says. However, a level of 5 sigma is necessary for a result to be considered truly significant. So other studies must be done to move from the level of “evidence” to the level of “discovery.”

In particle accelerators, the motion of colliding protons, heavy quarks, and their antiparticles sometimes provide energy that can evolve from this energy—these “external” quarks are not fundamental to the proton’s identity. On the other hand, it is a question of quarks that appear naturally, from time to time, in an unbounded proton, and therefore at low energy.

This phenomenon is rare, but may be of great importance for experiments carried out at the LHC. ” In CERN experiments, we create collisions between protons and look for subtle anomalies that could indicate new particles or forces. This is only possible if their nature is fully understood. “, concludes the physicist.

Source: NNPDF Collaboration, Nature