On the search for a narrow penta-quark Z$^+$ baryon in NN interactions

The possibility for an observation of a narrow penta-quark $Z^+$ baryon in $NN$ reactions is discussed. It is shown that the $pp{\to}n\Sigma^+K^+$ reaction at excess energies around 100 MeV above threshold provides optimal conditions for $Z^+$ baryon detection by an analysis of the $nK^+$ invariant mass spectrum, if the $Z^+$ mass is located around 1.5 GeV involving a rather narrow width.