[PAST EVENT] Physics Colloquium
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Marko Horbatsch, York University, Toronto, Canada. Title of Talk: Quantum interference in hydrogen spectroscopy and the proton charge radius puzzle
Abstract: For some years now the size of the proton charge radius has been in question. Atomic hydrogen spectroscopy was thought to be consistent with elastic electron-proton scattering determinations and yielding a radius of about 0.88 fm. The CREMA collaboration produced a 2S-2P Lamb shift measurement in muonic hydrogen (and later in muonic deuterium) from which the charge radius follows to have a value of 0.841 fm. This questions the accuracy of e-p scattering determinations of the charge radius. I will describe a recent fluorescence measurement from Garching (T. Haensch group, Science 2017) in regular hydrogen for the 2S-4P intervals, which when corrected for quantum interference yields a result that is consistent with the muonic hydrogen determination of the proton charge radius. The role of quantum interference in spectroscopy is a phenomenon that is becoming more important as the demand of determining the center of the resonance as a tiny fraction of its width is attempted.