Θ ∗ partner to the Θ ( 1540 ) baryon

If the exotic baryon Θ(1540) is udud¯ s with J P = 1 2 + , we predict that there is a Θ * (1540− 1680) with J P = 3 2 +. The width Γ(Θ * → KN) is at least a factor of three larger than Γ(Θ). The possibilities of Θ * → KN π or Θγ via M 1 and E2 multipoles are discussed. A major plank in establishing the constituent quark model was the absence of baryons with strangeness +1. The announcement of such a particle, Θ(1540), and with a narrow width is therefore startling [1], though there is still some debate as to its existence [2, 3]. It is thus important to seek further evidence of such hadrons in order to isolate the underlying dynamics of strong QCD. We show here that if Θ is udud¯ s with J P = 1/2 + , then the correlations among QCD forces necessarily imply there be Θ * , J P = 3/2 + , which is probably only a few tens of MeV more massive. When the proton is viewed at high resolution, as in inelastic electron scattering , its wavefunction is seen to contain configurations where its three " valence " quarks are accompanied by further q ¯ q in its " sea ". The three quark configuration is thus merely the simplest required to produce its overall positive charge and zero strangeness. The question thus arises whether there are baryons for which the minimal configuration cannot be satisfied by three quarks. The Θ would be an example; the positive strangeness requires an ¯ s and qqqq are required for the net baryon number, making what is known as a " pentaquark " as the minimal " valence " configuration. Hitherto unambiguous evidence for such states in the data has been lacking; their absence having been explained by the ease with which they would fall apart into a conventional baryon and a meson with widths of many hundreds of MeV. It is perhaps this feature that creates the most tantalising challenge