Correction to impulse approximation in pion-nucleus potential

The local density approximation is used to estimate the effects of correction to the impulse approximation in the first order pion-nucleus optical potential. The calculation indicates that at low pion kinetic energies (approximately or < 100 MeV), the correction changes the potential considerably and weakens both the real and imaginary parts. Even in the resonance region (pion kinetic energy approximately 200 MeV) the effects of this correction are large in the nuclear interior, although in the nuclear surface region these effects could be neglected. (auth.)