On isospin–breaking corrections to the energy level displacement of the ground state of kaonic hydrogen

In the model of low–energy K̄N interactions near threshold (EPJA 21, 11 (2004); 25, 79 (2005)) we calculate isospin–breaking corrections to the energy level displacement of the ground state of kaonic hydrogen, investigated by Meißner, Raha and Rusetsky (EPJC 35, 349 (2004)) within the non–relativistic effective Lagrangian approach based on ChPT by Gasser and Leutwyler. Our results agree well with those by Meißner et al.. In addition we calculate the dispersive corrections, caused by the transition Kp → K̄0n → Kp with the K̄0n pair on–mass shell. We show also how hypothesis on the dominant role of the K̄0n–cusp for the S–wave amplitude of low–energy Kp scattering near threshold, used by Meißner et al., can be realized in our approach. The result agrees fully with that by Meißner et al.. PACS: 36.10.–k, 11.10.Ef, 11.55.Ds, 13.75.Jz E–mail: [email protected], Tel.: +43–1–58801–14261, Fax: +43–1–58801–14299 Permanent Address: State Polytechnic University, Department of Nuclear Physics, 195251 St. Petersburg, Russian Federation E–mail: [email protected] E–mail: [email protected], Tel.: +43–1–58801–14261, Fax: +43–1–58801–14299 E–mail: [email protected] E–mail: [email protected], State Polytechnic University, Department of Nuclear Physics, 195251 St. Petersburg, Russian Federation E–mail: [email protected] State Polytechnic University, Department of Nuclear Physics, 195251 St. Petersburg, Russian Federation E–mail: [email protected]