Precision laser spectroscopy of antiprotonic helium and CPT violating limits on the antiproton charge and mass
Dr. Masaki Hori (MPQ Garching)

Antiprotonic helium is a Rydberg three-body atom composed of a helium nucleus, an electron, and an antiproton. We recently measured the optical transition frequencies of this atom to a precision of 10 parts per billion by laser spectroscopy.
By comparing this result with QED calculations, we determined the antiproton-to-electron mass ratio as 1836.152674(5). This measurement was carried out using a dye laser stabilized to an optical frequency comb generator. Since February, we started a new group at the Max Planck Institute for Quantum Optics in Garching, one of the purposes of which is to develop new techniques to measure this frequency to even higher precisions.