Improved Study of the Antiprotonic Helium Hyperfine Structure

TL;DR

This study enhances the precision of hyperfine structure measurements in antiprotonic helium using advanced laser and microwave spectroscopy, enabling better tests of fundamental symmetries like CPT invariance.

Contribution

It introduces improved measurement techniques that increase spectral precision and reduce linewidth, facilitating more accurate tests of antiproton properties and fundamental physics.

Findings

Spectral linewidth reduced by a factor of three

Measurement precision increased by a factor of five

Agreement with three-body QED calculations supports CPT tests

Abstract

We report the initial results from a systematic study of the hyperfine (HF) structure of antiprotonic helium (n,l) = (37,~35) carried out at the Antiproton Decelerator (AD) at CERN. We performed a laser-microwave-laser resonance spectroscopy using a continuous wave (cw) pulse-amplified laser system and microwave cavity to measure the HF transition frequencies. Improvements in the spectral linewidth and stability of our laser system have increased the precision of these measurements by a factor of five and reduced the line width by a factor of three compared to our previous results. A comparison of the experimentally measured transition frequencies with three body QED calculations can be used to determine the antiproton spin magnetic moment, leading towards a test of CPT invariance.