Physicists calculate proton's pressure distribution for first time

phys.org | 2/22/2019 | Staff
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Neutron stars are among the densest-known objects in the universe, withstanding pressures so great that one teaspoon of a star's material would equal about 15 times the weight of the moon. Yet as it turns out, protons—the fundamental particles that make up most of the visible matter in the universe—contain even higher pressures.

For the first time, MIT physicists have calculated a proton's pressure distribution, and found that the particle contains a highly pressurized core that, at its most intense point, is generating greater pressures than are found inside a neutron star.

Core - Proton - Center - Region - Pushes

This core pushes out from the proton's center, while the surrounding region pushes inward. (Imagine a baseball attempting to expand inside a soccer ball that is collapsing.) The competing pressures act to stabilize the proton's overall structure.

The physicists' results, published today in Physical Review Letters, represent the first time that scientists have calculated a proton's pressure distribution by taking into account the contributions of both quarks and gluons, the proton's fundamental, subatomic constituents.

Pressure - Aspect - Proton - Moment - Lead

"Pressure is a fundamental aspect of the proton that we know very little about at the moment," says lead author Phiala Shanahan, assistant professor of physics at MIT. "Now we've found that quarks and gluons in the center of the proton are generating significant outward pressure, and further to the edges, there's a confining pressure. With this result, we're driving toward a complete picture of the proton's structure."

Shanahan carried out the study with co-author William Detmold, associate professor of physics at MIT.

May - Physicists - US - Department - Energy

In May 2018, physicists at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility announced that they had measured the proton's pressure distribution for the first time, using a beam of electrons that they fired at a target made of hydrogen. The electrons interacted with quarks inside the protons in the target. The physicists then determined...
(Excerpt) Read more at: phys.org
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