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(π+,π−) and A(π−,π+) reactions in O16, Ca40, Rh103, and Pb208 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.
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d2σdΩdT for π+ mesons produced in π−p→π−π+n was measured at seven incident energies between 203 and 357 MeV and the integrated reaction cross section was calculated. The matrix element, when extrapolated to threshold and compared with soft-pion calculations, determined the chiral-symmetry-breaking parameter ξ=0.05±0.26, which is consistent with the Weinberg Lagrangian. The large hard-pion contributions at 203 MeV demonstrated the absolute necessity for comparing at threshold.
Axis error includes +- 0.0/0.0 contribution (?////).
We report measured asymmetries as a function of polar scattering angle for the reactions p¯p→π−π+ and p¯p→p¯p, using a polarized proton target. The annihilation data, obtained at a p¯ momentum of 1.64 GeV/c, are the first asymmetry data to be collected for this channel. A fit of these data and published differential cross section data is made by a partial-wave expansion, and the results are compared with a previous analysis. The elastic scattering data, obtained at 1.64 and 2.55 GeV/c, are fitted with an eight-parameter strong-absorption model.
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We report measured values of the asymmetry in the elastic scattering of K+ mesons from polarized protons. The data were obtained at fourteen incident K+ momenta from 1.33 to 2.58 GeVc; the approximate angular range covered was −0.85<cosθKc.m.<0.9. We compare our results with other available measurements and note several significant differences.
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