Archive Evidence for Substantial Charge Symmetry Violation in Parton Distributions C. Boros, J. T. Londergan, and A. W. Thomas Phys.
Nuclear physicists think of protons and neutrons as practically identical.
When they aim low-energy particle beams at nuclear targets, they find that the two behave in almost exactly the same way in the nucleus. But charge symmetry is harder to test accurately at high energies, and only the most recent experiments have had enough precision to do so. Physicists publishing in the 9 November PRL analyzed these recent results and found that there is a clear violation of charge symmetry at high energies, even after they accounted for all known sources of uncertainty. The authors conclude that more experiments are needed to verify the existence of this violation, which is inconsistent with the current understanding of quark properties. Blasting through steel.