Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 5: Theory I

HK 5.8: Talk

Monday, March 8, 2004, 17:45–18:00, D

Ground-state energy of pionic hydrogen to one loop — •E. Lipartia¹, J. Gasser², M.A. Ivanov³, M. Mojzis⁴, and A. Rusetsky⁵ — ¹Institute for Theoretical Physics (T39), TU München, Germany — ²ITP, Univesity of Bern, Bern Switzerland — ³BLTP, JINR, Dubna, Russia — ⁴Departmet of Physics, Univesity of Massachusetts, Amherst, USA — ⁵HISKP, Bonn Univesity, Bonn, Germany

We investigate the ground-state energy of the π−N atom (pionic hydrogen) in the framework of QCD and QED. In particular, we evaluate the strong energy-level shift. We perform the calculation at next-to-leading order in the low-energy expansion in the framework of infrared regularized effective field theory. The result provides a relation between the strong energy shift and the pion-nucleon S-wave scattering lengths - evaluated in pure QCD - at next-to-leading order in isospin breaking and in the low-energy expansion. We compare our result with available model calculations. Work supported by Swiss National Science Foundation.

• [1] J. Gasser, M.A. Ivanov, E. Lipartia, M. Mojzis, A. Rusetsky,
  [2] Eur.Phys.J.C26:13-34,2002.