Deeply bound 1s and 2p pionic states in [sup 205]Pb and effective pion mass in nuclear matter.

Recently we have succeeded in observing the 1s and 2p bound pionic states in [sup 205]Pb nucleus as well separated peaks in the excitation spectrum of the [sup 206]Pb(d,[sup 3]He) reaction. The observed spectrum agreed quite well with the theoretical prediction where the formation cross section was calculated for the deeply bound pionic states [1]. These states are accommodated in proximity to the nuclear surface as halo states in a potential provided by the attractive Coulomb and the repulsive core. The binding energies and the widths were precisely determined, and the values were used to deduce the unknown s-wave part of the π-nucleus interaction and to translate it to the effective pion mass in nuclear matter. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]