Annihilation range and final-state interaction in [Formula Presented] annihilation into [Formula Presented]

The large set of accurate data on differential cross section and analyzing power from the CERN LEAR experiment on [Formula Presented] in the range from 360 to [Formula Presented] is well reproduced within a distorted wave approximation approach. The initial [Formula Presented] scattering wave functions originate from a recent [Formula Presented] model. The transition operator is obtained from a combination of the [Formula Presented] and [Formula Presented] quark-antiquark annihilation mechanisms. A good fit to the data, in particular, the reproduction of the double-dip structure observed in the analyzing powers, requires quark wave functions for proton, antiproton, and pions with radii slightly larger than the respective measured charge radii. This corresponds to an increase in the range of the annihilation mechanisms, and consequently, the amplitudes for total angular momentum [Formula Presented] and higher are much larger than in previous approaches. The final-state [Formula Presented] wave functions, parametrized in terms of [Formula Presented] phase shifts and inelasticities, are also a very important ingredient for the fine tuning of the fit to the observables.