Nov 2 2022Reviewed by Mila Perera
Protons make up 95% of the observable universe’s mass, and new research from physicists at the University of New Hampshire is helping to understand how they interact. The findings are a yardstick for evaluating the strong force, one of nature’s four fundamental forces.
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There is a lot still unanswered about both of those things, the proton and the strong force. This brings us a little bit closer to that understanding. It is a necessary piece of two very fundamental things in the universe.
David Ruth, Study Lead Author and Ph.D. Candidate, University of New Hampshire
The interior components of the atom’s nucleus, including neutrons, protons, and the quarks and gluons that make them up, are held together by a strong force. Of the four fundamental forces of nature, gravity, electromagnetism, and the weak force, it is the least understood.
In the study, published in the journal Nature Physics, the researchers used an experiment exploring the spin of the protons in a regime, or mode of operation, where the quarks or elementary particles that make them up are at a great distance from each other to test two state-of-the-art, competing theoretical calculations of the strong force.
One of the calculations and their experimental results agreed, but not the other.
Theorists will now look closely at why the calculations do not agree since this type of physics study necessitates tight cooperation between theorists and experimentalists.
They explain that these calculations are extremely complex, that each theory group chooses a different method for carrying them out, and that some of the calculations conducted by theorists had different results. To better understand the strong force, they must establish which is right and which is wrong.
If we really want to understand our world, we have to have a solid theory of that force. I am not sure what the applications will be, but that understanding could push new technology in the future.
Karl Slifer, Study Lead Collaborator and Professor, Physics and Astronomy, University of New Hampshire
Similar to how our understanding of nucleon interactions a century ago gave rise to applications like fission, fusion, and nuclear power, Slifer can envision the study progressing from theoretical or experimental to practical applications.
It took a tiny army of graduate students, postdocs, and technical personnel six months to install and another six months to run the incredibly intricate research, which took ten years to complete.
The experiment was conducted at the Department of Energy’s Thomas Jefferson National Accelerator Facility, where it was the largest installation ever in Jefferson’s Hall A facility at the time.
The Department of Energy provided funding for the study under grant DE-FG02-88ER40410.
Ruth, D., et al. (2022) Proton spin structure and generalized polarizabilities in the strong quantum chromodynamics regime. Nature Physics. doi:10.1038/s41567-022-01781-y.