Diquarks and Exotic Spectroscopy

We propose that the recently discovered \Theta baryon is a bound state of four quarks and an antiquark, containing two highly correlated ud-pairs. If so, the \Theta baryon has positive parity, and it lies in an near-ideally mixed SU(3){f} $\overline{\mathbf{10}}${f} oplus $\mathbf{8}${f}. The Roper resonance and the P{11}(1710) fit naturally into this classification. We predict an isospin 3/2 multiplet of \Xi’s (S=-2) with J^{\Pi}=\half^{+} around 1750 MeV. A search for manifestly exotic \Xi^{+} and \Xi^{–} in this mass range could provide a sharp test of our proposal. We predict that charm and bottom analogues of the \Theta baryon are stable against strong decays.