Study of the rare hyperon decay Ω∓→Ξ∓π+π−

We report a new measurement of the decay Ω−→Ξ−π+π− with 76 events and a first observation of the decay Ω¯+→Ξ¯+π+π− with 24 events, yielding a combined branching ratio (3.74−0.56+0.67)×10−4. This represents a factor 25 increase in statistics over the best previous measurement. No evidence is seen for CP violation, with B(Ω−→Ξ−π+π−)=4.04−0.71+0.83×10−4 and B(Ω¯+→Ξ¯+π+π−)=3.15−0.89+1.12×10−4. Contrary to theoretical expectation, we see little evidence for the decays Ω−→Ξ1530∗0π− and Ω¯+→Ξ¯1530∗0π+ and place a 90% C.L. upper limit on the combined branching ratio B(Ω−(Ω¯+)→Ξ1530∗0(Ξ¯1530∗0)π∓)<7.0×10−5.