Neutron-proton charge exchange at high energies. A crucial reaction

The shape of the np→pn d(sigma)/dt is extraordinarily independent of energy throughout the range 1.5 less than or approximately equal to psub(L) less than or approximately equal to 25 GeV/c, despite the expected competition between π exchange with its associated background and rho, A2 exchange. The present analysis of this situation predicts a radical change beyond psub(L)=40 GeV/c if standard ideas about particle exchange are at all meaningful. It is also shown that the significant difference found at FNAL between the pp and pn total cross-sections, which probably indicates a break-down of Regge asymptotics, will strongly influence the np→pn reaction. Measurements of high-energy np charge exchange will therfore provide a crucial test for current theoretical ideas