Effective number of protons for quasifree ( pi -, pi 0) at 500 and 400 MeV

For the quasifree ([pi][sup [minus]],[pi][sup 0]) reaction on a wide range of targets at 500 and 400 MeV, the measured effective numbers of protons are found to be in good agreement with those from a simple semiclassical attenuation model based on the nuclear density and the total cross section for free [pi][ital N] scattering. The [ital A] dependence for our experimental results was fitted by a power law ([proportional to][ital A][sup [alpha]]), and the exponents [alpha] were found to be 0.38[plus minus]0.03 and 0.40[plus minus]0.06 for 500 and 400 MeV ([pi][sup [minus]],[pi][sup 0]), respectively.