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 made up of even smaller elementary particles known as quarks, which come in a variety of “flavors” or types: up, down, weird, lovely, bottom, and top.
It is generally believed that a proton is 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. Even stranger, when the proton contains the charm quark, the heavy particle only carries about half the mass of the proton.
The whole finding boils down to the probabilistic world of quantum physics. Although the charm quark is heavy, the chance of it appearing on a proton is quite small, so the large mass and the small chance basically cancel each other out.
Put another way, the entire mass of the charm quark is not absorbed by the proton, even if the charm quark is there, Science News reported.
Although protons are fundamental to the structure of atoms, which make up all matter, they are also very complicated.
Physicists don’t really know the fundamental structure of protons. Quantum physics holds that beyond the up and down quarks known to be present, other quarks could appear in protons from time to time, 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 of August
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 lot, so the researchers wanted to start with that one to find out if a proton could contain a quark heavier than itself. They did this by taking a new approach to 35 years of particle destruction data.
Related: Why Physicists Are Interested in the Mysterious Peculiarities of the Heaviest Quark
To learn about the structure of subatomic and elementary particles, researchers hurl particles at each other at breakneck speeds in particle accelerators such as the Large Hadron Collider, the world’s largest atom collider, located near Geneva.
Scientists with the nonprofit NNPDF collaboration collected this particle destruction data going back to the 1980s, including examples of experiments in which photons, electrons, muons, neutrinos, and even other protons smashed into protons.
By looking at the debris from these collisions, the researchers can reconstruct the original state of the particles.
In the new study, the scientists handed all of this collision data over to a machine learning algorithm designed to look for patterns without preconceived notions of 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 was not high enough for the researchers to declare the discovery of the charm quark in protons undeniable, but the results are the “first strong evidence” that it may be there, Forte said.
The structure of the proton is important, Forte said, because to discover new elementary particles, physicists will have to uncover minute differences between what is suggested by theories 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 a proton. Future experiments, like the planned Electron Ion Collider at Brookhaven National Laboratory in Upton, New York, may 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.