a Study of THETA(1720) in Hadronic J/psi Decay.

New results are obtained for the hadronic decays J/psi to phi{f} (1525) and phi theta(1720) from the Mark III detector at SPEAR. The results are based on 5.8 times 10^6 J/psi events. Using the relatively background free K ^+K^-K ^+K^- decay channel, we have extracted the five amplitudes describing the vector -tensor decay in both the f^'(1525) and theta(1720) mass regions. As in the case of radiative production from the J/ psi, the helicity structure of the decay is shown to be different in the two mass regions. Using a proper coherent fit to the full mass distribution we measure the product branching ratios: B(Jpsi to phi f^'(1525)) times B(f^'(1525) to KK) = (4.85 +/- 0.26 +/- 1.05) times 10^{-4} and B(J psi to phitheta(1720)) times B(theta(1720) to KK) = (3.08 +/- 0.48 +/- 0.67) times 10^{-4}. The analogous final state, where the tensor decays into K _sp{s}{0}K_sp {s}{0}, is used to check our conclusions.