Mainz 2022 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 73: Fundamental Symmetries II

HK 73.2: Group Report

Thursday, March 31, 2022, 16:30–17:00, HK-H9

Muonic X-ray measurements at the Paul Scherrer Institute — •Frederik Wauters — Johannes Gutenberg University Mainz, Germany

When negative muons are stopped in a target material, they are quickly captured and form an exotic atom. During this formation process, muonic X-rays, which can have energies up to several MeV, are emitted until the 1s orbital is reached. The muon wave function in the lower orbits has a large overlap with the nucleus, making this system an excellent laboratory to study short range interactions between the muon and the atomic nucleus such as finite size effects, nuclear capture, and possble parity odd interactions.

The muX project at the Paul Scherrer Institute is performing muonic X-ray measurements on medium and high-Z nuclei, deploying a large high-purity germanium array in combination with muon, electron and neutron detectors. A new technique was developed utilizing transfer reaction in a H2/D2 gas cell to stop a standard muon beam in a few ug of target material.

A wide physics program is focusing on atomic parity violation (APV) by measuring the the charge radius of 226Ra, which will serve as an important input for an upcoming APV experiment with Ra in a Paul trap. We are also pursuing measuring APV directly in muonic atoms in the 2s-1s transition. Furthermore, absolute nuclear charge radii measurements serve as a benchmark for laser spectroscopy, and nuclear muon capture gives access to highly excited nuclear states of interest to determine double beta-decay matrix elements.