Decays, contact P-wave interactions and hyperfine structure in Ω− exotic atoms

Contact P-wave interactions connected to the Larmor interaction of a magnetic dipole and Thomas spin precession in the filed of an electric quadrupole are described and their implications for spectroscopy of exotic Ω−-atoms are studied. In order to evaluate the magnitude of the contact P-wave interactions as compared to the conventional long-range interactions and the sensitivity of spectroscopic data to the Ω−-hyperon quadrupole moment, we consider 2P states of Ω− atoms formed with light stable nuclei with spins I⩾1/2 and atomic numbers Z⩽10. The energy level splitting caused by the contact interactions is 2–5 orders of magnitude smaller than the conventional long-range interactions. Strong decay widths of pΩ− atoms due to reactions pΩ−→ΛΞ0 and pΩ−→ΣΞ, induced by t-channel kaon exchanges, are calculated. Ω− atoms formed with the light nuclei have strong widths 5–6 orders of magnitude higher than splitting caused by the contact interactions. The low-L pattern in the energy spectra of intermediate- and high-Z Ω− atoms thus cannot be observed. The Ω− quadrupole moment can be measured by observing X-rays from circular transitions between high-L levels in Ω− exotic atoms. The effect of strong interactions in atoms is negligible starting from L∼10. The contact P-wave interactions exist in ordinary atoms and μ-meson atoms.