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Ground-state energy of pionic hydrogen to one loop |
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| Authors: | J Gasser MA Ivanov E Lipartia M Mojzis A Rusetsky |
| Institution: | (1) Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland , CH;(2) Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia , RU;(3) Department of Theoretical Physics 2, Lund University, Solvegatan 14A, 22362 Lund, Sweden , SE;(4) Laboratory of Information Technologies, Joint Institute for Nuclear Research, 141980 Dubna, Russia , RU;(5) High Energy Physics Institute, Tbilisi State University, University St. 9, 380086 Tbilisi, Georgia , GE;(6) Department of Physics, University of Massachusetts, Amherst, MA 01003, USA , US;(7) Department of Theoretical Physics, Comenius University, 28415 Bratislava, Slovakia , SK |
| Abstract: | We investigate the ground-state energy of the atom (pionic hydrogen) in the framework of QCD + 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 the relevant 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. Received: 11 June 2002 / Published online: 9 October 2002 |
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