SOFT BINARY-PROCESSES, NAMBU-JONA-LASINIO MODEL, AND ABSOLUTE VALUES OF THE AMPLITUDES FOR THE REACTIONS PI(-)P -] PI(0)N AND PI(-)P -] ETA-N

The reactions pi(-)p --> pi(0)n(eta n) and pi(-)p --> K(0)Lambda(Sigma ) proceed in two stages: (i) Gribov's diffusion of constituent quarks from each of the interacting hadrons in the space of rapidities and im pact parameters with the production of a flux tube having a fast spect ator at one end and a slow reagent at the other (this stage determines a power-law decrease of the amplitude with increasing energy) and (ii ) the charge exchange of slow reagents in the processes (u) over bar u --> (d) over bar d and (u) over bar u --> (s) over bar s, which deter mines the residue at the relevant Regge pole. The amplitude of the rea ction pi(-)p --> pi 0n(eta n) involves a bilinear form of scalars, ((u ) over bar u)((d) over bar d) = (P-3(0))(2), which determines the domi nant spin-orbit amplitude M-1(P-3(0)), and a bilinear form of pseudosc alars, ((u) over bar i gamma(5)u)((d) over bar i gamma(5)d) (S-1(0))(2 ). In the amplitude M-0, the terms (P-3(0))(2) and (S-1(0))(2) interfe re destructively and strongly. These facts, which follow from an analy sis of experimental data, comply with the predictions of the Nambu-Jon a-Lasinio (NJL) model. A spontaneous breakdown of chiral symmetry resu lts in that the weights of the bilinear forms prove to be independent of the coupling constant in the NJL Hamiltonian (blackness condition); in fact, they are determined by the squared transverse dimension R-2 of the charge-exchange region in the process ii u --> d d. In the expr ession for the physical amplitude, this dimension appears as the radiu s of the residue at the Regge pole. At small q(perpendicular to)(2), t he amplitude M-1(P-3(0)) involves the number of colors (N-c = 3), R-2, alpha, and alpha(0). For s = 8-400 GeV2 0.004 less than or equal to q (perpendicular to)(2) less than or equal to 0.1 (GeV/c)(2), comparison with the measured amplitude M-1(expt.) yields the \M-1(P-3(0))\/\M-1( expt.)\ values of 1.09(1 +/- 0.1) and 0.7(1 +/- 0.2) for the reactions pi(-)p --> pi(0)n and pi(-)p --> eta n, respectively. The reason for a strong breakdown of SU(3) symmetry-this breakdown is manifested in t he smallness of the observed amplitude for the reactions pi(-)p --> K0 Lambda(Sigma)-is discussed within the formally SU(3)-symmetric NJL mo del.