Hannover 2013 – scientific programme
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A: Fachverband Atomphysik
A 20: Poster: Precision spectroscopy of atoms and ions (with Q)
A 20.19: Poster
Tuesday, March 19, 2013, 16:00–18:30, Empore Lichthof
Precision Laser Spectroscopy of the 1S-2S Transition in Positronium — Paolo Crivelli1, David Cooke1, Aldo Antognini1, Klaus Kirch1,4, •Janis Alnis2, and Theodor W. Hänsch2, 3 — 1ETH Zurich, Institute for Particle Physics, CH-8093 Zürich — 2Max-Planck-Institut für Quantenoptik, 85748 Garching — 3Ludwig-Maximilians-Universität, 80799 München — 4Paul Scherrer Institute, Villigen, Switzerland
We aim to improve the current accuracy in the measurement of the energy interval of positronium (Ps) from its ground state (1S) to the first excited state (2S) by a factor of 5. This will provide a very stringent test of the theory describing atomic systems called bound states quantum electrodynamics (QED). Very recently a serious discrepancy of 5 sigma in the charge radius of the proton extracted from the muonic-hydrogen experiment at PSI compared to other experiments was found and has not yet been explained. This increases the importance of studying hydrogen-like and especially non-baryonic (with no quarks, e.g no protons) systems like positronium or muonium where finite-size effects due to the nucleus are absent. The proposed measurement will also result in the best determination of the positron-electron mass ratio that should be exactly one in order for the CPT symmetry to be conserved. This symmetry is a pillar of quantum field theory which is the base of our current understanding of particles and their interactions.