What have we learned from antiproton proton scattering?

Abstract

From recent charge exchange measurements in the extreme forward direction, an independent and precise determination of the pion nucleon coupling constant is possible. This determination has reopened the debate on the value of this fundamental coupling constant of nuclear physics. Precise measurements of charge exchange observables at forward angles below 900 MeV/c would also give a better understanding of the long range part of the two-pion exchange potential. For example, the confirmation of the coherence of the tensor forces from the pion exchange and the isovector two-pion exchange would be very valuable. With the present data first attempts at an $\NbarN$ partial wave analysis have been made where, as in nucleon nucleon scattering, the antinucleon nucleon high J partial waves are mainly given by one-pion exchange. Finally a recent $\pbarp$ atomic cascade calculation and the fraction of P-state annihilation in gas targets is commented on.Comment: 10 pages, Latex, to be published in Nucl. Phy

Calculation of the Doppler broadening of the electron-positron annihilation radiation in defect-free bulk materials

“…Systematic variations with atomic number have been observed for ratio curves with respect to Si for a number of elemental materials. 28 The calculation of the positron lifetime is not the central focus of our work, but it is a useful by-product. Comparisons between the calculated and experimental values of the positron lifetime was used by Barbiellini et al 17 to determine the value of the parameter ␣ used in the GGA to obtain the enhancement factors.…”