On the accuracy of the photon-difference method used in high-energy photonuclear experiments

Abstract

The accuracy in calculating the cross sections per photon, σ k, from a set of measured cross sections per equivalent γ quantum, σ q, is discussed. Four commonly used approximations for the bremsstrahlung spectrum and corrections for finite target thicknesses and collimator angles are reviewed. For the calculation of σ k a simple unfolding method is proposed which is known for solving the Fredholm integral equation of the first kind, and in which the necessary smoothing of the resulting curve is derived from the mean experimental error of σ q. For some examples of cross sections which may be encountered in photonuclear research above 100 MeV, the mean error of σ k caused by inaccurate knowledge of the bremsstrahlung spectra, by the unfolding method and by the experimental errors of σ q, is calculated.