Study of the rare hyperon decay Omega \to Xi π^+ π^-

Abstract

We report a new measurement of the decay Ω^- \to Ξ^- π^+ π^- with 76 events and a first observation of the decay Ω^+ \to Ξ^+ π^+ π^- with 24 events, yielding a combined branching ratio (3.74 ^{+0.67}_{-0.56}) \times 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^- \to Ξ^- π^+ π^-)=4.04^{+0.83}_{-0.71} \times 10^{-4} and B(Ω^+ \to Ξ^+ π^+ π^-)=3.15^{+1.12}_{-0.89} \times 10^{-4}. Contrary to theoretical expectation, we see little evidence for the decays Ω^- \to Ξ_{1530}^{*0} π^- and Ω^+ \to Ξ_{1530}^{*0} π^+ and place a 90% C.L. upper limit on the combined branching ratio B(Ω^-(Ω^+) \to Ξ^{*0}_{1530}(Ξ^{*0}_{1530}) π^\mp)<7.0 \times 10^{-5}.

6 pages, 5 figures, to be published in Phys. Lett. B