SMI Seminar on fundamental interactions and symmetries

The Hyperfine Puzzle of Strong-Field Bound-State QED

by Prof. Wilfried Nörtershäuser (Technische Universität Darmstadt)

Tuesday, 30 January 2018 from to (Europe/Vienna)
at SMI - Boltzmanngasse 3, 1090 Wien ( 3-2-08 - Seminarraum )
Description

Prof. Dr. Wilfried Nörtershäuser
Technische Universität Darmstadt

Abstract:

While quantum electrodynamics (QED) is usually referred to as the most accurately tested theory, its consistency for bound electrons in strong fields is still not proven with high accuracy. The strongest magnetic fields available in the laboratory are experienced by electrons bound in highly charged, heavy ions which can be probed by hyperfine transition spectroscopy.

The transition in lithium-like Bismuth was directly observed for the first time in 2011 at the experimental storage ring ESR located at GSI Darmstadt, but the accuracy of the result was limited by the imprecise knowledge of the ion velocity and the corresponding Doppler shift.

In a recent beamtime at the ESR, we were able to reduce the uncertainties in nearly all measured parameters and improved accuracy by more than an order of magnitude [1]. To our surprise, the result was more than 7 sigma off the theoretical prediction and has established the "Hyperfine Puzzle of QED" [2].

I will report on the experiment, its outcome, possible solutions of the Puzzle and further strategies to test strong-field bound-state QED with higher accuracy. 

[1] Nat. Commun., 8:15484 (2017)
[2] Nature Physics, 13, 553 (2017)