No abstract

Ne~experimental results on muon-catalyzed d-t fusion are reported. Unexpected target-density effects have been discovered both in dt p, molecular formation in t p, + 02 collisions and in the effective sticking probability. The dt p. formation rate is significantly enhanced at high density, presumably because of a strong three-body contribution. The origin of the observed reduction of the sticking probability at high density remains unclear. Both effects increase the number of fusions per muon that can be achieved; 150+ 4(stat.) + 20(syst.) fusions per muon have been observed.

A systematic study of inclusive pion double charge exchange is reported for nuclei between A = 16 and A =208. The doubly differential cross sections for the A(m. +,~) and A(m, m+) reactions in ' 0, Ca, ' Rh, and 'Pb were measured at incident energies between 120 and 270 MeV at three to five outgoing pion angles. Pion spectra were measured over the energy range from 10 MeV to the kinematic limit for double charge exchange. Integrating these spectra over outgoing pion energy generated angular distributions, and subsequently integrating these angular distributions generated total reaction cross sections. The shapes of the measured spectra are compared with those determined by the distribution of events in four-body phase space and with those predicted by a model in which the pion undergoes two sequential single charge exchanges on nucleons in a Fermi gas. The cross sections are compared with predictions of cascade calculations in which more than two interactions, including pion absorption and scattering without charge exchange, may occur. PACS number(s): 25.80.Gn, 25.80. Hp, 25.80.Ls major objective was to satisfy persistent curiosity about 'Present address: Continuous Beam Electron Accelerator Facility,

Measurements were made of the doubly differential cross sections for three inclusive pion reactions on 3 He: Ϫ double charge exchange ͑DCX͒, and ϩ and Ϫ inelastic scattering. The cross sections for DCX were measured at incident pion energies of 120, 180, and 240 MeV, and at angles of 25°, 50°, 80°, 105°, and 130°, while inelastic scattering cross sections were measured at 120, 180, and 240 MeV and scattering angles of 50°, 80°, 105°, and 130°. In each case the outgoing pion energy spectra were measured from 10 MeV up to the kinematic limit. The DCX spectra exhibit a double-peaked structure at forward angles that can be understood as a consequence of a sequential single charge exchange mechanism. Model calculations based on this mechanism are in rough agreement with the measured spectra. The doubly differential cross sections measured for the inelastic scattering reactions exhibit a prominent quasielastic peak. A distorted-wave impulseapproximation calculation of the quasielastic cross sections has been performed and a comparison made with the measurements. ͓S0556-2813͑97͒01204-1͔PACS number͑s͒: 25.80.Ek, 25.80.Gn, 25.80.Ls, 27.10.ϩh The earliest inclusive DCX measurements were made at the JINR Synchro-cyclotron in Dubna by Batusov et al. ͓1͔ using nuclear emulsions. Later experiments by Batusov et al. ͓2͔ and Gilly et al. ͓3͔ were performed in which total DCX cross sections on a range of nuclei from He to Pb were measured.

Measurements of the absolute neutron yield and the time dependence of the appearance of neutrons resulting from muon-catalyzed fusion have been carried out in high-density deuterium-tritium mixtures. The temperature dependence of the resonant d^ju-molecular formation process has been determined in the range 100 to 540 K. Mesomolecular formation is found to be resonant for DT as well as D 2 target molecules. The sticking probability and other fundamental parameters have been measured for the first time.