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arXiv · hep-ph/0206068

Ground-state energy of pionic hydrogen to one loop

J. Gasser·M. A. Ivanov·E. Lipartia·M. Mojzis·A. Rusetsky
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Abstract

We investigate the ground-state energy of the pi- p 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.

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J. Gasser, M. A. Ivanov, E. Lipartia, M. Mojzis, A. Rusetsky. 2002-08-16. Ground-state energy of pionic hydrogen to one loop. https://doi.org/10.1007/s10052-002-1013-z

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