Observation of parity violation in the Omega- ---> Lambda K- decay

The { alpha} decayparameter in the process { Omega}{ sup-} {yields} {Lambda}K{ sup-} has been measured from a sample of 4.50 million unpolarized { Omega}{ sup-} decays recorded by the HyperCP (E871) experiment at Fermilaband found to be [1.78 {+-} 0.19(stat) {+-} 0.16(syst)] x 10{ sup-2}. This is the first unambiguous evidence for a nonzero { alpha} decayparameter, and hence parity violation, in the { Omega}{ sup-} {Lambda}K{ sup-} decay.