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Redetermination of the strong-interaction width in pionic hydrogen

Abstract : The hadronic width of the ground state of pionic hydrogen has been redetermined by X-ray spectroscopy to be $\varGamma ^{\pi \mathrm {H}}_{1s}=(856\,\pm \,16_\mathrm{stat}\,\pm \,22_\mathrm{sys})$ 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$\alpha $, K$\beta $, and K$\gamma $ 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.
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Submitted on : Wednesday, October 6, 2021 - 4:12:42 PM
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A. Hirtl, D.F. Anagnostopoulos, D.S. Covita, H. Fuhrmann, H. Gorke, et al.. Redetermination of the strong-interaction width in pionic hydrogen. European Physical Journal A, EDP Sciences, 2021, 57 (2), pp.70. ⟨10.1140/epja/s10050-021-00387-x⟩. ⟨hal-03164348⟩



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