CORDIS - EU research results

Symmetry Tests in Experiments with Portable Antiprotons

Project description

Enhancing detection precision could shed light on the matter–antimatter imbalance

The Standard Model of particle physics, put forth in the1970s and modified along the way, is still the most complete description we have of our particle universe – nevertheless, it has acknowledged gaps. For every type of matter particle we have identified (12 total), there is a corresponding antimatter particle, or antiparticle. However, it is not clear why we observe so much more matter in the universe than antimatter. Normal 'baryonic' matter (protons, neutrons and electrons) makes up less than five percent of the universe. About a fourth seems to comprise invisible 'dark matter' and about 70 % a force that repels gravity known as dark energy. The EU-funded STEP project seeks to explore these mysteries through a high-precision study of protons and antiprotons made possible by isolating the latter from common sources of noise.


Our present understanding of particles and their fundamental interactions leaves us with extremely well tested theories in laboratory experiments, however cosmological observations indicate that our models are incomplete. Dark matter and dark energy are clearly not contained in our theories, and the baryon asymmetry in the universe cannot be reproduced from the Standard Model with its current parameters. Antiprotons offer the unique opportunity to make high-precision measurements at low energies in the antimatter sector and provide important tests of the fundamental interactions to search for a manifestation of new physics complementary to matter-based experiments. Here, I propose to extend the methods in low-energy antiproton precision measurements by developing a transportable antiproton reservoir. Relocating measurements from CERN’s antiproton decelerator into precision laboratories eliminates limitations from magnetic field noise in the antiproton decelerator hall and improves the precision by at least a factor of 30. I will also implement a novel method for ultra-precise cyclotron frequency measurements based on low-energy thermal-state selection for single antiprotons and quantum non-demolition measurements of the cyclotron energy. This leads to measurements at 300-fold reduced temperature compared to the state-of-art methods. Using these two methods, I will improve the most precise test of CPT invariance in the baryon sector by at least a factor of 70 and demonstrate charge-to-mass ratio comparisons with unprecedented precision. I will also set first limits on the interaction of light dark matter and antiprotons by searching for topological defects by simultaneous measurements of the antiproton cyclotron frequency in two separate experiments. The developments provide also methods to test whether the weak equivalence principle holds for charged antimatter by comparing the gravitational redshift of protons and antiprotons at different altitudes.

Host institution

Net EU contribution
€ 585 472,64
40225 Dusseldorf

See on map

Nordrhein-Westfalen Düsseldorf Düsseldorf, Kreisfreie Stadt
Activity type
Higher or Secondary Education Establishments
Total cost
€ 585 472,64

Beneficiaries (2)