易胜博官网

New research from a team of physicists led by 易胜博官网 significantly advances our understanding of how protons, which comprise 95% of the universe, interact with each other. The results, published recently in the journal , provide a benchmark for testing the strong force, one of the four fundamental forces in nature.

鈥淭here鈥檚 a lot still unanswered about both of those things, the proton and the strong force,鈥� says lead author David Ruth, a Ph.D. candidate at 易胜博官网. 鈥淭his brings us a little bit closer to that understanding. It鈥檚 a necessary piece of two very fundamental things in the universe.鈥�

The strong force governs how what鈥檚 internal to the atom鈥檚 nucleus 鈥� neutrons, protons and the quarks and gluons that make them up 鈥� bind together. It is the least understood of the four fundamental forces of nature, which include gravity, electromagnetism and the weak force.

鈥淚f we really want to understand our world, we have to have a solid theory of that force,鈥� says professor of physics , Ruth鈥檚 advisor and a lead collaborator on the study.

鈥淭here鈥檚 a lot still unanswered about both ... the proton and the strong force. This brings us a little bit closer to that understanding. It鈥檚 a necessary piece of two very fundamental things in the universe.鈥�

The researchers tested two state-of-the-art, competing theoretical calculations of the strong force with an experiment probing the spin of the protons in a regime, or mode of operating, where the quarks that comprise them are at a great distance from each other. Their experimental findings agreed with one of the calculations but not the other.

鈥淏ecause these calculation are very complex, each theory group makes different choices about how to do them,鈥� Ruth says about the discrepancy. 鈥淒ue to some choice the theorists made in these calculations, they ended up different. If we鈥檙e going to understand the strong force, we need to know which one is right, which one is wrong.鈥�

Not only were the calculations extremely complex, the experiment itself was no walk in the park. It was conducted a decade ago at the Department of Energy鈥檚 Thomas Jefferson National Accelerator Facility; at that time it was the largest ever installation in Jefferson Lab鈥檚 Hall A facility.

鈥淚t took a small army of graduate students, post-docs and technical staff six months to install and another six months to run,鈥� says Slifer , who led the experiment in 2021, in a that accompanies the article. 鈥淎long the way we faced many technical challenges.鈥� Ruth, who will finish his Ph.D. in the coming year, analyzed data from the experiment but was not present for it.

The next step in the inquiry into the strong force, says Ruth, is back in the theorists鈥� hands. 鈥淎 lot of physics is the theorists and the experimentalists tossing balls to each other. We鈥檙e tossing the ball back to the theorists and saying, 鈥榃hy don鈥檛 your calculations agree? What needs to be done for them to agree?鈥欌��

Slifer can imagine the work moving out of the theoretical or experimental and into practical applications, much as our understanding of interactions between nucleons a century ago gave birth to applications like fission and fusion and nuclear power. 鈥淚鈥檓 not sure what the applications will be, but that understanding will push new technology in the future,鈥� he says.

In addition to Ruth and Slifer, 易胜博官网 co-authors on the study were former 易胜博官网 postdoctoral researcher James Maxwell,听now a staff scientist at Jefferson Lab; former graduate students Ryan Zielinski and Toby Badman; assistant professor ; former postdoc Sara Phillips;听and the late assistant professor of physics Patricia Solvignon-Slifer. The work was funded by several grants, including grant DE-FG02-88ER40410 to 易胜博官网.

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