Search for deeply-bound pionic states using (p,2He) reactions at 390.6 MeV

Deeply-bound pionic states in 207Pb have been searched for using the 208Pb(p,2He) reaction at 0° with a 390.6 MeV proton beam. The spectrum near the threshold for free π− production shows contributions from π− bound states. The spectrum for 12C taken with the same experimental method shows no signature of pionic bound states, and is explained to be composed of a flat continuum and the contribution of quasi-free π− production process.