Pionic hydrogen

D. Gotta, F. Amaro, D. F. Anagnostopoulos, S. Biri, D. S. Covita, H. Gorke, A. Gruber, M. Hennebach, A. Hirtl, T. Ishiwatari, P. Indelicato, Th Jensen, E. O.Le Bigot, J. Marton, M. Nekipelov, J. M.F. dos Santos, S. Schlesser, Ph Schmid, L. M. Simons, Th StrauchM. Trassinelli, J. F.C.A. Veloso, J. Zmeskal

Research output: Chapter in Book/Report/Conference proceedingChapter

57 Citations (Scopus)


Strong-interaction shift ε1s and broadening Γ1s in the pionic hydrogen atom are determined from the energies and line widths of X-ray transitions to the 1s ground state. They are directly connected to the πN scattering lengths which are related to the πN coupling constant and the πN sigma term being a measure of chiral symmetry breaking. Therefore, the measurement of the pion-nucleon s-wave scattering lengths constitutes a high-precision test of the methods of chiral perturbation theory (XPT), which is the low-energy approach of QCD. Additional constraints for the πN scattering lengths are obtained from the measurement of the ground-state shift in pionic deuterium. The hadronic width is linked to s-wave pion production in nucleon-nucleon collisions. A new experiment, set up at the Paul Scherrer Institut (PSI), has finished taking data recently and will allow the determination of the scattering lengths at the few per cent level.

Original languageEnglish
Title of host publicationPrecision Physics of Simple Atoms and Molecules
EditorsSavely G Karshenboim, Savely G. Karshenboim
Number of pages21
Publication statusPublished - Feb 18 2008

Publication series

NameLecture Notes in Physics
ISSN (Print)0075-8450


ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Gotta, D., Amaro, F., Anagnostopoulos, D. F., Biri, S., Covita, D. S., Gorke, H., Gruber, A., Hennebach, M., Hirtl, A., Ishiwatari, T., Indelicato, P., Jensen, T., Bigot, E. O. L., Marton, J., Nekipelov, M., dos Santos, J. M. F., Schlesser, S., Schmid, P., Simons, L. M., ... Zmeskal, J. (2008). Pionic hydrogen. In S. G. Karshenboim, & S. G. Karshenboim (Eds.), Precision Physics of Simple Atoms and Molecules (pp. 165-185). (Lecture Notes in Physics; Vol. 745). https://doi.org/10.1007/978-3-540-75479-4_10