The alpha and helion particle charge radius difference from spectroscopy of quantum-degenerate helium

2023/06/04 by van der Werf, Y., Steinebach, K., Jannin, R. +2 · 1 citation
#Atomic Physics (physics.atom-ph) #FOS: Physical sciences #Nuclear Experiment (nucl-ex)

paper · doi:10.48550/arxiv.2306.02333

Abstract

Accurate spectroscopic measurements of calculable systems provide a powerful method for testing the Standard Model and extracting fundamental constants. Recently, spectroscopic measurements of finite nuclear size effects in normal and muonic hydrogen resulted in unexpectedly large adjustments of the proton charge radius and the Rydberg constant. We measured the 2³S→2¹S transition frequency in a Fermi gas of ³He with an order of magnitude higher accuracy than before. Together with a previous measurement in a ⁴He Bose-Einstein condensate, a squared charge radius difference r²_h - r²_α = 1.0757(15) fm² is determined between the helion and alpha particle. This measurement provides a benchmark with unprecedented accuracy for nuclear structure calculations. A deviation of 3.6σ is found with a determination (arXiv:2305.11679) based on spectroscopy of muonic helium ions.

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• Recent Progress in Ab-Initio Nuclear Theory for Precision Physics Searches in Muonic Atoms and Superallowed β Decays

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