DECAY PROPERTIES OF THE E HYPERON AND E RESONANCES

A sample of 2500 {Xi}{sup -} and 500 {Xi}{sup 0} hyperons, produced in {Xi}K, {Xi}K{pi}, and {Xi}K{pi}{pi} final states by K{sup -} (in H{sub 2}) at incident momenta of 1.7 to 2.7 BeV/c, has been analyzed. The data are from an exposure (K-63) of 26 events/{mu}b in the 72-inch bubble chamber; approximately 85% of the {Xi}{sup -} events and 60% of the {Xi}{sup 0} events have been analyzed. For the {Xi}, they determine the spin and decay parameters a{sub {Xi}} and {Phi}{sub {Xi}} = tan{sup -1} ({beta}{sub {Xi}}/{Gamma}{sub {Xi}}). Combining their data with 900 {Xi}{sup -} and 150 {Xi}{sup 0} events from an earlier experiment (K-72), they obtain the following results: (1) {Xi} spin - J = 1/2 favored over J = 3/2 by {approx} 2.5 standard deviations; (2) {Xi} decay parameters (assuming a{sub {Lambda}} = 0.647 {+-} 0.048) - a{sub {Xi}{sup -}} = -0.398 {+-} 0.041, {Phi}{sub {Xi}{sup -}} = 9.8{sup o} {+-} 9.0{sup o}; a{sub {Xi}{sup 0}} = -0.413 {+-} 0.104. They observe {Xi}*(1530) and {Xi}*(1817); their data are insufficient for analysis of suggested {Xi}* resonances at 1705 and 1933 MeV. They measure the {Xi}*(1530) electromagnetic mass difference {Delta}m = m({Xi}*{sup -}) = m({Xi}*{sup 0}) = 2.0 {+-} 3.2 MeV. Using data, part of which has already been described, they find for {Xi}*(1530): J {ge} 3/2 favored over J = 1/2 (the J = 1/2 hypothesis is {approx} 3.5% as probable as the J = 3/2 hypothesis); J{sup P} = 3/2{sup +} favored over 3/2{sup -} by {approx} 2.8 standard deviations. For {Xi}*(1817) decaying into {Xi}*(1530) + {pi}, the hypotheses J{sup P} = 1/2{sup +}, 1/2{sup -}, 3/2{sup -}, 5/2{sup +}, 7/2{sup -}, etc. (corresponding to {ell} = 1, 2, 0 and 2, 1 and 3, and 2 and 4, respectively) are favored over other hypotheses, but results are inconclusive due to large background