Room for an S = +1 pentaquark in K^+ - nucleus phenomenology
  Evidence for excitation of exotic S=+1 pentaquark degrees of freedom is presented by studying optical-potential fits to K^+ - nucleus total, reaction and elastic-differential cross section data at p(lab) = 500 - 700 MeV/c. Estimates of the underlying two-nucleon absorption K^+ n N --> Theta^+ N reaction cross section are made and are used for discussing the anticipated cross section of the strangeness exchange reaction K^+ N --> pi Theta^+. 
A. Gal and E. Friedman