X-ray measurements in helium-like atoms increased discrepancy between experiment and theoretical QED

Abstract

A recent 15 parts per million (ppm) experiment on muonic hydrogen (p+μ-) found a major discrepancy with quantum electrodynamics (QED) and independent nuclear size determinations. Here we find a significant discrepancy in a different type of exotic atom: a medium-Z nucleus with two electrons. Investigation of the data collected is able to discriminate between available QED formulations and reveals a pattern of discrepancy of almost six standard errors of experimental results from the most recent theoretical predictions, with a functional dependence proportional to Zn where n ≃ 4. In both the muonic and highly charged systems, the sign of the discrepancy is the same, with the measured transiti..