Quasi-free pion photoproduction from carbon above 300 MeV

The momentum spectra of charged pions produced in the reaction ¹²C(γ, π^±) have been measured for incident photon energies in the interval between 300 and 850 MeV in steps of 50 MeV. Pions with relatively high momenta have been detected by a magnetic spectrometer set at the lab angles 28.4° and 44.2°. All these spectra exhibit a clear singly peaked structure. Detailed features of the structure are quantitatively investigated and compared with a plane-wave impulse-approximation calculation. Calculated results are found to reproduce the spectral shape very well and the absolute magnitude is also rather well fitted by introducing the pion absorption effect properly.