Precision Laser Spectroscopy of Leptonic Atoms
Dr. Paolo Crivelli (ETH Zürich)

Positronium (the positron and electron bound state, Ps) and Muonium (the positive muon-electron bound system, Mu) are made of two leptons which are believed to be point like particles. These purely leptonic atoms are thus free from the finite-size effects which are increasingly important in H spectroscopy. A renewed interest in these atomic systems has been triggered by the recent results of the muonic hydrogen experiment at PSI that gave rise to the so called proton charge radius puzzle. Furthermore, weak interaction effects are negligible at the current level of experimental accuracy, and thus these systems provide an excellent testing ground for bound-state QED and a way for the determination of fundamental constants such as the positron electron mass ratio, the muon mass and the charge ratio between the first two generation of leptons. The 1S-2S transition frequencies have been measured in the past for both systems reaching a precision of the order of few ppb.
In this seminar, we will present the status of our experiments aiming to improve the uncertainty of the current measurements.