Soft binary processes and the phenomenology of confinement

A three-stage model of the charge-exchange reactions {pi}{sup -}p {yields} flux tube {pi}{sup 0}n is considered. The first stage ({pi}{sup -}p {yields} flux tube) is the formation of a flux tube by the annihilation of a mesonic {bar u} quark and a protonic u quark at low relative rapidity. The second stage is the stretching of the flux tube, with the d and ud spectators placed at its ends, with the relative rapidity lns. The third stage is the rupture of the flux tube (flux tube {yields} {pi}{sup 0}n), resulting in the production of a d{bar d} pair with low relative rapidity, followed by the evolution of the flux tube fragments into a physical {pi}{sup 0}n system. The analysis of experimental data in this model leads to the following conclusions: (1) in the spin-flip amplitude, the annihilation (production) of quarks occurs predominantly in the {sup 3}P{sub 0} state; (2) the annihilation probability in this state is close to unity, so that the annihilating quarks can be called {open_quotes}black{close_quotes}; (3) in the non-spin-flip amplitude, the {sup 3}P{sub 0} mode interferes destructively with other annihilation modes (e.g., {sup 1}S{sub 0}); (4) the parameters of quark annihilation prove to be identical in themore » reactions {pi}{sup -}p {yields} {pi}{sup 0}n and {pi}{sup -}p {yields} {eta}n, while the observables of these reactions (i.e., cross sections, the ratio of the spin-flip amplitude to the non-spin-flip amplitude, etc.), from which the quark-annihilation parameters are deduced, differ strongly in magnitude. The quark-annihilation parameters for charge-exchange reactions are compared with the corresponding quantities for the production of ordinary resonances in the Isgur-Kokoski model. 26 refs., 3 figs., 5 tabs.« less