Room for anS=+1pentaquark inK+-nucleus phenomenology

Abstract

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 ${p}_{\mathrm{lab}}~500\text{\ensuremath{-}}700$ MeV/c. Estimates of the underlying two-nucleon absorption ${K}^{+}\mathit{nN}\ensuremath{\rightarrow}{\ensuremath{\Theta}}^{+}N$ reaction cross section are made and are used for discussing the anticipated cross section of the strangeness exchange reaction ${K}^{+}N\ensuremath{\rightarrow}\ensuremath{\pi}{\ensuremath{\Theta}}^{+}$.