Measurement of the Xi(0)->Lambda gamma decay asymmetry and branching fraction - NA48 collaboration

In data taken with the NA48 experiment at the CERN SPS in 1999, 730 candidates of the weak radiative hyperon decay Xi(0) --> Lambdagamma have been found with an estimated background of 58 +/- 8 events. From these events the Xi(0) --> Lambdagamma decay asymmetry has been determined to alpha(Xi(0) --> Lambdagamma) = -0.78 +/- 0.18(stat) +/- 0.06(syst), which is the first evidence of a decay asymmetry in Xi(0) --> Lambdagamma. The branching fraction of the decay has been measured to be Br(Xi(0) --> Lambdagamma) = (1.16 +/- 0.05(stat) +/- 0.06(syst)) x 10(-3). (C) 2004 Elsevier B.V. All rights reserved.