Neutron-proton charge exchange

Abstract
We have studied the role of one- and two-pion exchange in the neutron-proton charge exchange cross section and spin-transfer variables. The cross section shows a scaling behavior over a wide energy range, consistent with a one-meson-exchange amplitude, and the spin-transfer observables are nearly invariant on a finite (but smaller) energy range. It is suggested that these data can be understood in terms of the exchange of pions between the quark constituents of the nucleon.