  According to QCD, there exists a broken dynamical supersymmetry between an
antiquark and a diquark. This supersymmetry can be used to relate the mass of a
pentaquark to the mass of an antibaryon by replacing two antiquarks in an
antibaryon by two diquarks to form a pentaquark. Using this technique, we find
that the mass of an exotic pentaquark with strangeness plus 1 is greater than
1.74 GeV, or at least 200 MeV larger than that of the reported $\Theta^+$
pentaquark. Furthermore, there is no reason for the pentaquark to be narrow; on
the contrary, it is expected to be so broad that it will be difficult to
observe.
