COUPLED-CHANNEL ANALYSIS OF LOW-ENERGY NUCLEON ANTINUCLEON INTERACTIONS

A multichannel M-matrix method is applied to the NNBAR system, taking into account elastic ppBAR scattering, charge exchange ppBAR --> nnBAR, and ppBAR annihilation. In contrast to previous descriptions, the M-matrix elements are treated as real functions. The isospin breaking in the M matrix is taken into account. We describe the differential and total cross sections for ppBAR --> ppBAR and ppBAR --> nnBAR, the cross section sigma(tot)(ppBAR), and the real-to-imaginary ratio of the forward amplitude of elastic ppBAR scattering up to beam momenta p(lab) = 600 MeV/c. The fit leads to a resonance in the s wave at about p(lab) = 500 MeV/c and to bound states in the p wave near the ppBAR threshold.