Diquarks and exotic spectroscopy

We propose that the recently discovered [Formula presented] baryon is a bound state of four quarks and an antiquark, containing two highly correlated [Formula presented] pairs. If so, the [Formula presented] has positive parity, and it lies in an near-ideally mixed [Formula presented] [Formula presented]. The Roper resonance and the [Formula presented] fit naturally into this classification. We predict an isospin [Formula presented] multiplet of [Formula presented]’s ([Formula presented]) with [Formula presented] around 1750 MeV. A search for manifestly exotic [Formula presented] and [Formula presented] in this mass range could provide a sharp test of our proposal. We predict that charm and bottom analogs of the [Formula presented] may be stable against strong decays.