Exploring Helium Nucleus Beyond Ground State.
A new electron-scattering experiment has remeasured the transition from the ground state to the first excited state of the helium nucleus, confirming a discrepancy with theoretical predictions. The results provide new insights into the spatial structure of the excited state and touch on fundamental questions about our understanding of nuclear interactions. The discrepancies imply that the form factor may serve as a tool for probing small contributions to nuclear forces, but researchers need a better understanding of the theoretical uncertainties.