Coupled-channels study of antiproton-proton reactions.

Abstract

Low energy antiproton-proton elastic, charge exchange, charged pion, and charged kaon production reactions are studied in a coupled-channels model. The need for a coupled-channels approach to antiproton-proton reactions is first demonstrated. Meson exchange potentials describe the long-range N\ifmmode\bar\else\textasciimacron\fi{}N interaction; smooth phenomenological forms are used for the N\ifmmode\bar\else\textasciimacron\fi{}N interaction at short distances. Effective channels are introduced to simulate strong absorptive effects, such as multimeson production processes. Transition potentials for kaon and pion production are derived in coordinate space and shown to include an important spin-times-derivative coupling form. These transition potentials, along with a one-boson-exchange model with effective absorptive channels, are used to determine the role of multistep processes of the type \ensuremath{\pi}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\pi}\ensuremath{\leftrightarrows}p\ifmmode\bar\else\textasciimacron\fi{}p\ensuremath{\leftrightarrows}n\ifmmode\bar\else\textasciimacron\fi{}n\ensuremath{\leftrightarrows}K\ifmmode\bar\else\textasciimacron\fi{}K. Control over such coupled-channels effects is sought as a step toward unfolding short-distance quark effects in a reliable way. The p\ifmmode\bar\else\textasciimacron\fi{}p elastic and charge exchange differential cross sections at three p\ifmmode\bar\else\textasciimacron\fi{}p laboratory momenta (780, 690, and 590 MeV/c) are examined first, since ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$ and ${K}^{\mathrm{\ensuremath{-}}}$${K}^{+}$ data also exist at these energies. Results are then presented that manifest strong coupling effects, especially between the pion and kaon production channels. Based on that result, a full coupled-channels fit to the p\ifmmode\bar\else\textasciimacron\fi{}p, n\ifmmode\bar\else\textasciimacron\fi{}n, ${K}^{\mathrm{\ensuremath{-}}}$${K}^{+}$, and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$${\ensuremath{\pi}}^{+}$ data is presented and analyzed.