https://doi.org/10.1140/epja/s10050-021-00387-x
Regular Article – Experimental Physics
Redetermination of the strong-interaction width in pionic hydrogen
1
Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Kegelgasse 27, 1030, Vienna, Austria
2
Department of Materials Science and Engineering, University of Ioannina, 45110, Ioannina, Greece
3
Laboratory for Particle Physics, Paul Scherrer Institute, 5232, Villigen, Switzerland
4
LIBPhys, Physics Department, University of Coimbra, 3004-526, Coimbra, Portugal
5
Zentralinstitut für Elektronik, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
6
Institut für Kernphysik, Forschungszentrum Jülich, 52425, Jülich, Germany
7
Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University, Collège de France, 4, place Jussieu, 75005, Paris, France
8
Institut für Theoretische Physik Universität Zürich, 8057, Zürich, Switzerland
9
Institut des NanoSciences de Paris, CNRS, Sorbonne Université, 4 place Jussieu, 75005, Paris, France
10
I3N, Department of Physics, Aveiro University, 3810, Aveiro, Portugal
11
Atominstitut, TU Wien, 1020, Vienna, Austria
12
Bosch Termotecnologia, S.A., EN 16-Km 3,7, 3800-533, Cacia Aveiro, Portugal
13
Department of Radiology and Nuclear Medicine, General Hospital of the City of Vienna, 1090, Vienna, Austria
14
DAHER Nuclear Technologies GmbH, 63457, Hanau, Germany
15
Ringkjøbing Gymnasium, Vasevej 24, 6950, Ringkjøbing, Denmark
16
Physics Department, National Tsing Hua University, 300, Hsinchu, Taiwan
17
WTI GmbH, 52428, Jülich, Germany
Received:
2
October
2020
Accepted:
4
February
2021
Published online:
23
February
2021
The hadronic width of the ground state of pionic hydrogen has been redetermined by X-ray spectroscopy to be 
meV. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institute by using the cyclotron trap and a high-resolution Bragg spectrometer with spherically bent crystals. Coulomb de-excitation was studied in detail by comparing its influence on the line shape by measuring the three different transitions K
, K
, and K
at various hydrogen densities. The pion-nucleon scattering lengths and other physical quantities extracted from pionic-atom data are in good agreement with the results obtained from pion-nucleon and nucleon-nucleon scattering experiments and confirm that a consistent picture is achieved for the low-energy pion-nucleon sector with respect to the expectations of chiral perturbation theory.
© The Author(s) 2021
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