[ad_1]
Something about atoms has never been added. The fundamental particles called quarks become slow when taken in crowds of protons and neutrons – and frankly, they should not.
For decades, physicists have been looking for clues about the quark's tendency to slow down in larger atoms, but they came back empty-handed. But now, a closer look at the old data has finally revealed a clue to explain this strange phenomenon.
A large team of physicists known as CLAS Collaboration (from the CEBAF Wide Acceptance Spectrometer) recently analyzed data collected from previous experiments conducted in the accelerator facility. of continuous electron beams from the Jefferson lab.
Their goal was to find evidence supporting one of two possible explanations of why the fundamental units that form protons and neutrons – a family of particles called quarks – have less dynamics inside larger atoms.
The phenomenon was observed for the first time by the European Muon Collaboration in the early 1980s, which observed a difference in the behavior of nuclear particles when they bind in large atoms such as iron, compared to smaller atoms like hydrogen.
In what has been called the EMC effect, it soon became clear that the larger the atoms, the slower their quarks were.
Quarks, however, are relatively high-energy particles, making them divas to share the scene. When linked as triplets to form protons or neutrons, there should be no difference if the quarks are in a nucleus or flowing freely in the wild.
"Two main models currently describe this effect," said Douglas Higinbotham, a nuclear physicist at Jefferson Lab.
"One model is that all the 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 lies in a kind of short-range relationship that appears briefly when different groups of quarks enter the scope.
"That said that many protons and neutrons behave as if they were free, while others are involved in short – range correlations and are heavily modified," Higinbotham said.
By analyzing old data on the scattering of electrons that bounced off protons and neutrons inside atoms of carbon, aluminum, lead, and iron, the researchers been able to develop a universal function that describes the EMC effect.
Their description is based on the possibility of a short, short-range relationship between a neutron and a proton when they touch each other.
"We now have this function, where we have correlated neutron-proton pairs, and we think that it can describe the CEM effect," says physicist Barak Schmookler, currently a researcher at Stony University. Brook in the United States.
This confirms the second model that quarks act differently only in certain circumstances, for example when the right combination of protons and neutrons snuggles closer than usual. Otherwise, nuclear particles and their quarks act as free agents.
In terms of quantum physics, this intimate affair is a compatible overlap of structure that gives each set of quarks a little more freedom to move. Increase the space in which a particle can be found and reduce the momentum that it can have.
"In quantum mechanics, every time you increase the volume of a confined object, it slows down," says Axel Schmidt, postdoctoral fellow at MIT's Laboratory for Nuclear Science.
"If you tighten the space, it speeds up .It is a known fact."
This universal function explains perfectly why quarks slow down more in larger atoms. With more neutrons in the area, each proton is more likely to find love. Therefore, to say.
It also means that we can abandon the old idea that this loss of momentum is an essential feature of quarks that congregate in large nuclei.
"The image of this model is that all protons and neutrons, when they are stuck together in a nucleus, all their quarks begin to slow down," Schmidt says.
"And this model suggests that most protons and neutrons continue as if nothing had happened, and that it is the selected protons and neutrons that are in those pairs that actually have a significant shift in their quarks."
The discovery is not enough, however, to definitively close the book on this mystery. Later experiments at the Jefferson Lab will provide details on how protons move in much less congested nuclei, deuterium, the proton-neutron aroma of hydrogen atoms.
For now, this is a pretty convincing explanation of the EMC effect, which adds a tiny detail to the dance party at the heart of nuclear physics.
This research was published in Nature.
[ad_2]
Source link