Quarks inside the particles seem to move more than they should in an electric field:
The subatomic particles are built of smaller particles called quarks, which are bound together by a powerful interaction known as the strong force. New experiments seem to show that the quarks respond more than expected to an electric field pulling on them, physicist Nikolaos Sparveris and colleagues report October 19 in Nature. The result suggests that the strong force isn't quite as strong as theory predicts.
It's a finding at odds with the standard model of particle physics, which describes the particles and forces that combine to make up us and everything around us. The result has some physicists stumped about how to explain it — or whether to even try.
"It is certainly puzzling for the physics of the strong interaction, if this thing persists," says Sparveris, of Temple University in Philadelphia.
Such stretchiness has turned up in other labs' experiments, but wasn't as convincing, Sparveris says. The stretchiness that he and his colleagues measured was less extreme than in previous experiments, but also came with less experimental uncertainty. That increases the researchers' confidence that protons are indeed stretchier than theory says they should be.
[...] Pascalutsa says he's often eager to dive into puzzling problems, but the odd stretchiness of protons is too sketchy for him to put pencil to paper at this time. "You need to be very, very inventive to come up with a whole framework which somehow finds you a new effect" to explain the bump, he says. "I don't want to kill the buzz, but yeah, I'm quite skeptical as a theorist that this thing is going to stay."
It will take more experiments to get theorists like him excited about unusually stretchy protons, Pascalutsa says. He could get his wish if Sparveris' hopes are fulfilled to try the experiment again with positrons, the antimatter version of electrons, scattered from protons instead.
Journal Reference:
Li, R., Sparveris, N., Atac, H. et al. Measured proton electromagnetic structure deviates from theoretical predictions. Nature (2022). 10.1038/s41586-022-05248-1
(Score: 3, Interesting) by PiMuNu on Wednesday October 26 2022, @12:14PM
The key is fig. 4, which shows a significance of about 1-2 sigma. The mean discrepancy between theory and data is smaller than previous measurements, the errors are also smaller. There are now several results all showing significance at about 1-2 sigma at the same electron energy, with no equivalent result at other electron energies. If one assumes all the experiments are statistically independent, there is about a 0.1-1 % chance that it is a fluke.
https://arxiv.org/abs/2210.11461 [arxiv.org]