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Physicists have finally solved a basic mystery about the inside of the atom

Something about atoms has never put up. Basic particles called quarks get nice when they are stuck in lots of protons and neutrons – and quite frankly they shouldn't. For decades, physicists have been searching for clues on the quark's tendency to slow down in larger atoms, but have come up in empty hands. But now a closer look at old data has revealed a clue to explain this strange phenomenon. A massive group of physicists called CLAS Collaboration (after CEBAF Large Acceptance Spectrometer) recently ran data collected from previous experiments at the Jefferson Labs Continuous Electron Beam Accelerator Facility. Their goal was to find evidence to support one of two potential explanations why the basic units that form protons and neutrons &#821 1; a family of particles called quarks – have less momentum in larger atoms. The phenomenon was first noticed by Europe's Muon Collaboration in the early 1980s, which observed a difference in how nuclear particles appeared while they were bound in large atoms as iron, compared to smaller ones like hydrogen. In what came to be known as the EMC effect, it quickly became clear that the larger atoms became, the slower their quark became. Quarks are quite high energy sources on articles but make them divas when it comes to sharing the scene. Once bound as triplets to form protons or neutrons, it should not make a difference if the quarks are in a nucleus or run free through the wild yonder. "There are currently two…

Something about atoms has never put up. Basic particles called quarks get nice when they are stuck in lots of protons and neutrons – and quite frankly they shouldn’t.

For decades, physicists have been searching for clues on the quark’s tendency to slow down in larger atoms, but have come up in empty hands. But now a closer look at old data has revealed a clue to explain this strange phenomenon.

A massive group of physicists called CLAS Collaboration (after CEBAF Large Acceptance Spectrometer) recently ran data collected from previous experiments at the Jefferson Labs Continuous Electron Beam Accelerator Facility.

Their goal was to find evidence to support one of two potential explanations why the basic units that form protons and neutrons &#821

1; a family of particles called quarks – have less momentum in larger atoms.

The phenomenon was first noticed by Europe’s Muon Collaboration in the early 1980s, which observed a difference in how nuclear particles appeared while they were bound in large atoms as iron, compared to smaller ones like hydrogen.

In what came to be known as the EMC effect, it quickly became clear that the larger atoms became, the slower their quark became.

Quarks are quite high energy sources on articles but make them divas when it comes to sharing the scene. Once bound as triplets to form protons or neutrons, it should not make a difference if the quarks are in a nucleus or run free through the wild yonder.

“There are currently two main models describing this effect,” says Douglas Higinbotham, a nuclear physicist from Jefferson Lab.

“One model is that all protons and neutrons in a nucleus [and thus their quarks] are modified and they are all modified in the same way.”

Another explanation suggests that the answer resides in a kind of short-range relationship that briefly pops up when different groups of quarks are within the range.

“It says that many protons and neutrons appear as if they are free, while others are involved in short-range correlations and are highly modified,” says Higinbotham.

By analyzing old data on the spread of electrons, protons and neutrons bounce in carbon atoms, aluminum, lead, and iron, the researchers could come up with a universal function that describes the EMC effect.

Their description is based on the risk of a short relationship between a neutron and a proton when they are affected.

” Now we have this feature, where we have correlated neutron proton pairs, and we think it can describe the EMC effect, says physicist Barak Schmookler, now a researcher at Stony Brook University in the United States.

This supports the second model that states that quarks work only under certain circumstances, for example, when the right combination of proton and neutron snuggles closer than usual. Otherwise, the core particles and quarks function as free agents.

In quantum physics terms, this intimate business is a compatible structure overlap that gives each set of quarks a little more freedom to roam. Increase the space that a particle can be found in, and you reduce the momentum it can have.

“In quantum mechanics, whenever you increase the volume over which an object is limited, it slows down,” says Axel Schmidt, a postdoc student at MIT’s nuclear science laboratory.

“If you tighten up space, it goes up. It’s a known fact.”

This universal function accurately explains why quarks slow down more in larger atoms. With more neutrons in the local area, each proton has a greater chance of finding love. So to speak.

It also means that we can ditch the old idea that this loss of momentum is a core feature of quarks that they collect in large nuclei.

“The picture before this model is that all protons and neutrons, when stuck together in a core, all quarks begin to slow down,” says Schmidt.

“And what this model suggests is that most protons and neutrons continue as nothing has changed, and it is the chosen protons and neutrons found in these pairs that really have a significant change in their quarks.”

The discovery is not enough to definitely close the book about this mystery, though. Follow-up experiments at Jefferson Lab will provide details on how protons move in the much less narrow nuclei, the deuterium-proton-neutron flavor of hydrogen atoms.

For now, however, it is quite a convincing explanation for the EMC effect, and one that adds a little detail to the dance party in the heart of nuclear physics.

This research was published in Nature .

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