Isospin analysis of Theta+ production forbids gamma p ---> Theta+ K(s) and allows gamma n ---> Theta+ K-.

Abstract

The discrepancy between + photoproduction on proton vs. deuteron can be resolved if the photon couples much more strongly to K+K− than to Ko ¯K o as indicated by the experimentally observed asymmetry between p → (1520)K+ and n → (1520)Ks. Significant signal-background interference effects can occur in experiments like N → ¯K + which search for the + as a narrow I = 0 resonance in a definite final state against a nonresonant background, with an experimental resolution coarser than the expected resonance width. We show that when the signal and background have roughly the same magnitude, destructive interference can easily combine with a limited experimental resolution to completely destroy the resonance signal. Whether or not this actually occurs depends critically on the yet unknown relative phase of the I = 0 and I = 1 amplitudes. We discuss the implications for some specific experiments.