Pion emission in 2H, 12C, 27Al, gamma pi+ reactions at threshold
  The first data from MAX-lab in Lund, Sweden on pion production in photonuclear reactions at threshold energies, is presented. The decrease of the total yield of pi+ in gamma + 12C, 27Al reactions below 200 MeV as well as differential, dsigma/dOmega, cross sections follow essentially predictions from an intranuclear cascade model with an attractive potential for pion-nucleus interaction in its simplest form. Double differential, d2sigma/dOmegadT, cross sections at 176 MeV show, however, deviations from the model, which call for refinements of nuclear and Coulomb potentials and possibly also for coherent pion production mechanisms. 
P. Golubev, V. Avdeichikov, K.G. Fissum, B. Jakobsson, I. A.   Pshenichnov, W.J. Briscoe, G.V. O'Rielly, J. Annand, K. Hanse...