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

TL;DR

This paper reports a new measurement of the rare hyperon decay Omega to Xi pi pi, with increased statistical precision, and finds no evidence of CP violation or decay to the Xi* resonance, challenging some theoretical expectations.

Contribution

It provides the first observation of Omega+ decay to Xi+ pi+ pi- and significantly improves the measurement of the decay's branching ratio, with implications for hyperon decay models.

Findings

Measured combined branching ratio (3.74^{+0.67}_{-0.56}) x 10^{-4}

No evidence of CP violation in the decay

Set upper limit on decay to Xi* resonance at 7.0 x 10^{-5}

Abstract

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}.