Strange quantum experiment shows protons have more ‘charm’ than we thought

A new study suggests that protons may have more “charm” than we thought.

The proton is one of the subatomic particles that make up the nucleus of an atom. No matter how small protons are, they are made up of even smaller elementary particles. (will open in a new tab) known as quarks, which come in many different “flavors” or types: up, down, strange, charm, down, and up. The proton is usually considered to be composed of two up quarks and one down quark.

But a new study shows that things are much more complicated. Protons can also contain a charmed quark, an elementary particle whose mass is 1.5 times the mass of the proton itself. Stranger still, when the proton does contain a charmed quark, the heavy particle still carries about half the mass of the proton.

All conclusions are reduced to the probabilistic world of quantum physics. (will open in a new tab). Although a charmed quark is heavy, the probability of it occurring in a proton is quite small, so a large mass and a low probability basically cancel each other out. In other words, the entire mass of the charmed quark is not absorbed by the proton, even if the charmed quark is there, according to Science News. (will open in a new tab).

Although protons form the basis of the structure of atoms (will open in a new tab) — which make up all matter — they are also very complex. Physicists don’t really know the fundamental structure of protons. Quantum physics believes that in addition to the known up and down quarks, other quarks can turn into protons from time to time, Stefano Forte, a physicist at the University of Milan, told the Nature Briefing podcast. (will open in a new tab). Forte has co-authored a new paper showing evidence for the charm of quarks in protons, published in the journal Nature. (will open in a new tab) Aug. 17.

There are six types of quarks. Three of them are heavier than protons, and three are lighter than protons. The charm quark is the lightest of the heavy group, so the researchers wanted to start with it to see if the proton could contain a quark heavier than itself. They did this by applying a new approach to 35 years of particle collision data.

On the subject: why physicists are interested in the mysterious quirks of the largest quark (will open in a new tab)

To learn about the structure of subatomic and elementary particles, researchers slam particles into each other at breakneck speeds in particle accelerators such as the Large Hadron Collider, the world’s largest atomic accelerator, located near Geneva. Scientists with the non-profit NNPDF collaboration have been collecting this devastating data since the 1980s, including examples of experiments in which photons, electrons, muons, neutrinos (will open in a new tab)our and even other protons crashed into protons. By looking at the debris from these collisions, researchers can reconstruct the original state of the particles.

In the new study, the scientists fed all this collision data to a machine learning algorithm designed to look for patterns without any preconceived notions of what the structures might look like. The algorithm returned the possible structures and the probability that they could actually exist.

The study revealed a “small but not negligible” chance of finding a quark charm, Forte said in an interview with Nature Briefing. The level of evidence was insufficient for researchers to announce the undeniable discovery of a charmed quark in protons, Forte said, but the results are “the first hard evidence” that it might exist there.

The structure of the proton is important, Forte says, because to discover new elementary particles, physicists will have to find minute differences between what theories suggest and what is actually observed. This requires extremely precise measurements of subatomic structures.

For now, physicists still need more data on the elusive “charm” inside the proton. Future experiments, such as the planned Electron-Ion Collider at Brookhaven National Laboratory in Upton, New York, could help, Tim Hobbs, a theoretical physicist at the FermiLab in Batavia, Illinois, told Science News.

Originally published on Live Science.

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