SMI Seminar on fundamental interactions and symmetries

Testing Quantum Electrodynamics in strong fields with Exotic Atoms

by Paul Indelicato (CNRS et Université Pierre et Marie Curie)

SMI - Vienna

This Seminar had been planned as a hybrid-event. Unfortunaltely, due to the lockdown joining in person is not an option anymore. 
If you wish to join online please send an email to martin.simon at by Tue. 30th of Nov. 2021 to request the zoom-link.


Comparing high-precision, low-energy experimental results to accurate theoretical values, e.g., in atomic and molecular physics is one of the ways to test the standard model. The accuracy of quantum electrodynamics tests in strong fields with highly-charged ions (HCI) is limited by uncertainties on the nuclear size contribution to transition energies of the heaviest elements (see, e.g., [1] and Refs. there in). We have shown [2] that using circular Rydberg states in exotic atoms could provide a way to test QED in strong fields, free from nuclear uncertainties. Moreover, the mean-electric field in these systems can be well above the Schwinger limit of spontaneous-pair creation, giving a special role to vacuum polarization. I will present these theoretical results, which involve muonic and antiprotonic atoms and report on a new experimental result on muonic Ne, obtained in the framework of the HEATES collaboration at JPARC in Japan. In this experiment we used a “transition edge sensor” (TES) microcalorimeters [3, 4] and a low-pressure gas target (0.1, 0.4 and 0.9 atm). This is the first time a TES microcalorimeter has been used for a precision experiment on exotic atoms created in a gas target to reduce electron recapture. A previous precise experiment has been performed with a TES on pionic carbon, using a solid graphite target [5]. I will compare the results on muonic Ne to previous crystal spectrometer measurements on muonic atoms and to state-of-the art HCI results. I will then describe future plans for measurements on heavier muonic atoms at JPARC and on antiprotonic atoms on the ELENA ring at CERN. I will also briefly discuss other exotic atoms of interest.

[1] Topical Review: QED tests with highly-charged ions,
P. Indelicato. J. Phys. B 52, 232001 (2019).
[2] Testing Quantum Electrodynamics with Exotic Atoms,
N. Paul,  G. Bian,  T. Azuma,  S. Okada and P. Indelicato. Phys. Rev. Lett. 126, 173001 (2021).
[3]  X-ray spectroscopy of muonic atoms isolated in vacuum with transition edge sensors,
S. Okada, et al. J. Low Temp. Phys. 200, 445–451 (2020).
[4] Testing Quantum Electrodynamics: High Precision X-ray Spectroscopy of Muonic Neon Atoms,
T. Okumura, et al. in preparation (2021).
[5] First application of superconducting transition-edge sensor microcalorimeters to hadronic atom X-ray spectroscopy,
S. Okada, et al. Progress of Theoretical and Experimental Physics 2016, 091D01 (2016).

Dr. Angela Gligorova

Organized by

Stefan Meyer Institute