Exploring New Frontiers in Precision Antimatter Spectroscopy

The observed imbalance between matter and antimatter in the universe motivates high-precision comparisons of their fundamental properties. At CERN’s Antiproton Decelerator, the BASE collaboration performs such tests using advanced cryogenic Penning traps. We have achieved the most precise proton-to-antiproton charge-to-mass ratio comparison to date, with a fractional uncertainty of 16 parts per trillion [1], and developed a novel spectroscopy technique enabling the first direct high-precision measurement of the antiproton magnetic moment with 1.5 parts-per-billion accuracy [2]. Together with our latest proton magnetic moment measurement [3], this improves the precision of magnetic moment-based CPT symmetry tests by more than a factor of 3,000. A time-series analysis of magnetic moment data further allowed us to set the first direct constraints on antiproton–axion-like particle (ALP) interactions [4], and, more recently, to derive constraints on ALP–photon conversion [5] using ultra-sensitive single-particle detection.

In parallel, we are developing new technologies for sympathetic antiproton cooling [6] and quantum-logic-inspired spectroscopy [7]. A particularly groundbreaking achievement is the development of the transportable antiproton trap BASE-STEP, which enables the relocation of precision antiproton spectroscopy experiments from the accelerator environment to dedicated laboratory space at Heinrich Heine University Düsseldorf. The first successful transport of trapped antiprotons marks a transformative step in antimatter research, opening entirely new possibilities for high-precision experiments in controlled environments.

In this talk, I will provide a general introduction to the field, review recent BASE results, and highlight our latest advances toward a tenfold improved coherent measurement of the antiproton magnetic moment and the pioneering work on antiproton transport.

[1] M. J. Borchert et al., Nature 601, 35 (2022).

[2] C. Smorra et al., Nature 550, 371 (2017). 

[3] G. Schneider et al., Science 358, 1081 (2017).

[4] C. Smorra et al., Nature 575, 310 (2019). 

[5] J. A. Devlin et al., Phys. Rev. Lett. 126, 041321 (2021). 

[6] M. A. Bohman et al. Nature 596, 514 (2021)

[7] J. M Conrejo et al., New J. Phys. 23 073045