Observation of Ξ(1620)^{0} and Evidence for Ξ(1690)^{0} in Ξ_{c}^{+}→Ξ^{-}π^{+}π^{+} Decays

Area of Science:

• Particle Physics
• High Energy Physics
• Nuclear Physics

Background:

• Hyperon resonances with strangeness S=-2 are not fully understood.
• The Ξ(1620)⁰ has been theorized but not experimentally confirmed.

Purpose of the Study:

• To report the first observation of the double strange baryon Ξ(1620)⁰.
• To measure the mass and width of the Ξ(1620)⁰.
• To search for evidence of the Ξ(1690)⁰.

Main Methods:

• Analysis of a 980 fb⁻¹ data sample collected with the Belle detector.
• Studying decays of the Ξ_{c}^{+} baryon into Ξ⁻π⁺π⁺.
• Utilizing the KEKB asymmetric-energy e⁺e⁻ collider.

Main Results:

• First observation of the Ξ(1620)⁰ in Ξ⁻π⁺ decays.
• Measured mass: 1610.4 ± 6.0(stat)⁺⁶.1₋₄.₂ (syst) MeV/c².
• Measured width: 59.9 ± 4.8(stat)⁺².⁸₋₇.₁ (syst) MeV.
• 4.0σ evidence for the Ξ(1690)⁰ was obtained.

Conclusions:

• The observation of Ξ(1620)⁰ provides crucial data for understanding hyperon resonances.
• These findings contribute to the ongoing exploration of the particle physics landscape.
• Further studies are warranted to fully characterize these S=-2 hyperon states.