Speaker
Description
Muonic atom spectroscopy is a well-established method to accurately determine the root-mean-square (RMS) radii of nuclear charge density distributions and has already delivered the most accurate results for very light (Z < 3) as well as heavier nuclei (Z > 10). However, a gap remains for muonic atoms from lithium to neon due to technological limitations in the relevant energy range (~20–200 keV) based on the lack of resolving power of conventional solid-state detectors.
To address this gap, the QUARTET collaboration employs cryogenic metallic magnetic calorimeters (MMCs) that combine broadband spectral coverage with record resolving power. In October 2024, the first experimental campaign at the Paul Scherrer Institute demonstrated the feasibility of this approach and showed the first high-resolution spectra of muonic lithium, beryllium, and boron, resolving the 2p-1s transitions of the individual stable isotopes. These results mark a significant step forward in bridging the low-Z charge radius gap and offer promising prospects for future precision measurements.
