Formation of deeply bound pionic atoms and pion properties in nuclei

Abstract

We study theoretically the formation of the deeply bound pionic atoms in various cases to deduce the pion properties in nuclei precisely from the observables. We show the angular dependence of the pionic atom formation spectra of the 122 Sn(d, 3 He) reactions in the forward angles. At each scattering angle, a different combination of the pion-bound and neutron-hole states dominates the spectrum because of the kinematical condition. We conclude that we can obtain information on the deeply bound pionic 2p state in addition to the 1s and 2s states by observing the spectra in finite angles. We also consider the neutron-odd nucleus as a target nucleus of the formation reaction, because it has an advantage that the pionic atom is formed in the even-even nucleus, of which the ground state has no neutron-hole states. In the 117 Sn(d, 3 He) reaction, we find that we can see clearly the peak structure of the pionic 1s state formation with the ground state of the even-even nucleus 116 Sn. The pionic atom in the even-even nucleus will not have additional shifts induced by the effects of the residual interaction between pion-bound and neutron-hole states. The observation of these pionic states is preferable for extracting the accurate information on the pion properties from data.