Precise laser spectroscopy of antimatter atoms, and metrological determination of the proton-to-electron mass ratio

Goal of this project is to synthesize artificial atoms made of antimatter particles, and study their properties at the highest possible precision using the latest laser spectroscopic techniques developed at the Max-Planck Institute for Quantum Optics.

Every kind of particle in nature has a corresponding antiparticle with the same (or so it is believed) mass and opposite electric charge. For example, the antiparticle of the proton is called an antiproton. These antiparticles are always produced in pairs with their normal particle counterparts; they annihilate when they come into contact with matter. It is believed that at the beginning of the universe, matter and antimatter were created in almost equal amount; it is one of the great mysteries of particle physics and cosmology why given this apparent symmetry, our universe ended up being so matter-dominated.

At the Antiproton Decelerator facility of CERN, our experimental group synthesized an exotic atom called "antiprotonic helium". This is a three-body system composed of an antiproton, helium nucleus, and electron. We then measured the characteristic transition frequencies of this atom by laser spectroscopy. From this we determined the ratio between the antiproton and electron mass to a precision of better than 1 part in 100 million. Within the MAP collaboration, we are currently developing advanced non-linear spectroscopic techniques to improve this experimental precision to even further. This is of vital importance, since any deviation between the antiproton mass and charge and those of the proton's, however small, would indicate that one of the fundamental symmetries between matter and antimatter is broken.