Isospin effects in antinucleon-nucleon scattering and annihilation

Isospin effects in NN\ifmmode\bar\else\textasciimacron\fi{} scattering and annihilation are studied here using the optical model. Real part of the effective NN\ifmmode\bar\else\textasciimacron\fi{} potential was chosen to be the G-parity-transformed Bonn NN potential (OBEPQ). Parameters of the imaginary part of the optical potential were obtained by fitting the total pp\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}pp\ifmmode\bar\else\textasciimacron\fi{}, pp\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}nn\ifmmode\bar\else\textasciimacron\fi{}, and n\ifmmode\bar\else\textasciimacron\fi{}p\ensuremath{\rightarrow}n\ifmmode\bar\else\textasciimacron\fi{}p cross sections to averaged experimental data represented here by analytical formulas. The model reproduces reasonably well the differential and total cross sections of NN\ifmmode\bar\else\textasciimacron\fi{} scattering and charge-exchange reactions as well as the characteristics of p\ifmmode\bar\else\textasciimacron\fi{} atoms. There is no evident relationship between the peculiar behavior of the real-to-imaginary ratio of the pp\ifmmode\bar\else\textasciimacron\fi{} forward elastic scattering amplitude and isospin effects.

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