Protons may have more “charm” than we thought, new research suggests.
A proton is one of the subatomic particles that make up the nucleus of an atom. As small as protons are, they are composed of even smaller elementary particles known as quarks, which come in several “flavors” or types: up, down, strange, charm, bottom, and top.
Typically, a proton is thought to be made up of two up quarks and one down quark. But a new study finds it’s more complicated than that.
Protons can also contain a charm quark, an elementary particle that is 1.5 times the mass of the proton itself. Stranger still, if the proton contains the charm quark, the heavy particle still only carries about half the mass of the proton.
The finding all boils down to the probabilistic world of quantum physics. Although the charm quark is heavy, the chances of it forming in a proton are quite small, so the high mass and the low probability actually cancel each other out.
In other words, the entire mass of the charm quark is not taken up by the proton, even if the charm quark is there, Science News reported.
While protons are fundamental to the structure of atoms – which make up all matter – they are also very complex.
Physicists don’t really know the fundamental structure of protons. According to quantum physics, in addition to the up and down quarks that are known to be present, other quarks may occasionally pop up in protons, Stefano Forte, a physicist at the University of Milan, told the Nature Briefing podcast.
Forte co-authored the new paper showing evidence for the charm quark in protons, published in the journal Nature 17 Aug.
There are six types of quarks. Three are heavier than protons and three are lighter than protons. The charm quark is the lightest of the heavy batch, so researchers wanted to start with that to find out if a proton could contain a quark heavier than itself. They did this by approaching 35 years of particle-destroying data in a new way.
Related: Why Physicists Are Interested in the Mysterious Oddities of the Heaviest Quark
To learn more about the structure of subatomic and elementary particles, researchers smash particles against each other at blistering speeds at particle accelerators such as the Large Hadron Collider, the world’s largest nuclear destroyer, near Geneva.
Scientists with the nonprofit NNPDF collaboration collected this particle-destroying data dating back to the 1980s, including examples of experiments where photons, electrons, muons, neutrinos and even other protons crashed into protons.
By looking at the debris from these collisions, researchers can reconstruct the particles’ original state.
In the new study, the scientists transferred all of this collision data to a machine-learning algorithm designed to look for patterns without preconceptions about what the structures might look like.
The algorithm returned possible structures and the probability that they could actually exist.
The study found a “small but not negligible” chance of finding a charm quark, Forte told Nature Briefing. The level of evidence wasn’t high enough for the researchers to explain the charm quark’s undeniable discovery in protons, but the results are the “first solid evidence” it may be, Forte said.
The structure of the proton is important, Forte said, because to discover new elementary particles, physicists will have to discover tiny differences in what theories suggest and what is actually observed. This requires extremely accurate measurements of subatomic structures.
For now, physicists still need more data about the elusive “charm” in a 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 Fermilab in Batavia, Illinois, told Science News.
This article was originally published by Live Science. Read the original article here.
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