Hadronic shift in pionic hydrogen

nucl-ex

/ Authors

M. Hennebach, D. F. Anagnostopoulos, A. Dax, H. Fuhrmann, D. Gotta, A. Gruber, A. Hirtl, P. Indelicato, Y. -W. Liu, B. Manil

and 5 more authors

V. E. Markushin, A. J. Rusi el Hassani, L. M. Simons, M. Trassinelli, J. Zmeskal

/ Abstract

The hadronic shift in pionic hydrogen has been redetermined to be $ε_{1s}=7.086\,\pm\,0.007(stat)\,\pm\,0.006(sys)$\,eV by X-ray spectroscopy of ground state transitions applying various energy calibration schemes. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals.