Study of the Rare Hyperon Decay (Omega)#-+# → Ξ#-+# π+π-

The authors report a new measurement of the decay (Omega)- → Ξ- π+π- with 76 events and a first observation of the decay (bar (Omega))+ → (bar Ξ)+ π+π- with 24 events, yielding a combined branching ratio (3.74-0.56+0.67) x 10-4. This represents a factor 25 increase in statistics over the best previous measurement. No evidence is seen for CP violation, with Β((Omega)- → Ξ- π+π-) = 4.04-0.71+0.83 x 10-4 and Β((bar (Omega))+ → (bar Ξ)+ π+π-) = 3.15-0.89+1.12 x 10-4. Contrary to theoretical expectation, they see little evidence for the decays (Omega)- → Ξ*15300 π- and (bar (Omega))+ → (bar Ξ)*15300 π+ and place a 90% C.L. upper limit on the combined branching ratio Β((Omega)-((bar (Omega))+) → Ξ*15300 ((bar Ξ)*15300)π#-+#) < 7.0 x 10-5.