Effective number of protons for quasifree (π−,π0) at 500 and 400 MeV

For the quasifree (${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^0$) 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 πN scattering. The A dependence for our experimental results was fitted by a power law (∝${\mathit{A}}^{\mathrm{\alpha }}$), and the exponents α were found to be 0.38±0.03 and 0.40±0.06 for 500 and 400 MeV (${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^0$), respectively.