Deeply bound π- states in 207Pb formed in the 208Pb(d,3He) reaction.: I.: Experimental method and results -: art. no. 025201

The deeply bound pionic states (1s,2p)(pi)-x Pb-207 were observed for the first time, by investigating the Pb-208(d,He-3) reaction at a beam energy of T-d=604.3 MeV and at ejectile angles around 0 degrees. The measured momentum distribution of the He-3 particles was used to determine the Q value spectrum in the region - 145 MeV<Q< - 120 MeV with a systematic uncertainty of +/-120 keV and a full width at half maximum resolution of 480+/-60 keV. This spectrum shows a prominent peak at Q similar or equal to - 135.5 MeV, corresponding to the pionic 2p state, coupled mainly to the 3p(1/2) and 3p(3/2) neutron hole states in Pb-207. A shoulder is seen on the tail of this dominant peak, and is attributed to the population of the pionic 1 s state. The cross section for the continuum component at these high excitation energies is d(2)sigma/(d Ohm dE) = 4.7 mu b/sr MeV. The net cross section for production of pi(-) states in the bound pion region - 140 MeV<Q< -133 MeV above the continuum amounts to d sigma/d Ohm = 76 mu b/sr.