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

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 Added by Oleg Kamaev
 Publication date 2010
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and research's language is English




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



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Using a data sample of 980~fb$^{-1}$ collected with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we present evidence for the $Omega(2012)^-$ in the resonant substructure of $Omega_{c}^{0} to pi^+ (bar{K}Xi)^{-}$ ($(bar{K}Xi)^{-}$ = $K^-Xi^0$ + $bar{K}^0 Xi^-$) decays. The significance of the $Omega(2012)^-$ signal is 4.2$sigma$ after considering the systematic uncertainties. The ratio of the branching fraction of $Omega_{c}^{0} to pi^{+} Omega(2012)^- to pi^+ (bar{K}Xi)^{-}$ relative to that of $Omega_{c}^{0} to pi^{+} Omega^-$ is calculated to be 0.220 $pm$ 0.059(stat.) $pm$ 0.035(syst.). The individual ratios of the branching fractions of the two isospin modes are also determined, and found to be ${cal B}(Omega_{c}^0 to pi^+ Omega(2012)^-) times {cal B}(Omega(2012)^- to K^-Xi^0)/{cal B}(Omega_{c}^0 to pi^+ K^- Xi^0)$ = (9.6 $pm$ 3.2(stat.) $pm$ 1.8(syst.))% and ${cal B}(Omega_{c}^0 to pi^+ Omega(2012)^-) times {cal B}(Omega(2012)^- to bar{K}^0 Xi^-)/{cal B}(Omega_{c}^0 to pi^+ bar{K}^0 Xi^-)$ = (5.5 $pm$ 2.8(stat.) $pm$ 0.7(syst.))%.
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