Observation of an Excited Ω− Baryon

Abstract

Using data recorded with the Belle detector, we observe a new excited hyperon, an Ω^{*-} candidate decaying into Ξ^{0}K^{-} and Ξ^{-}K_{S}^{0} with a mass of 2012.4±0.7(stat)±0.6(syst) MeV/c^{2} and a width of Γ=6.4_{-2.0}^{+2.5}(stat)±1.6(syst) MeV. The Ω^{*-} is seen primarily in ϒ(1S),ϒ(2S), and ϒ(3S) decays.

Ω baryon spectrum and their decays in a constituent quark model

“…(iii) The other first orbital excited state Ω(1 2 P 1/2 − ) whose mass is predicted to be ∼ 1950 MeV within the Lattice QCD [13] and the relativized quark models [5,6]. The measured ΞK invariant mass distributions from Belle show that there is a weak enhancement around 1950 MeV [15], which may be a weak hint of…”

“…They are determined by fitting the masses of four Ω resonances: (i) The ground state Ω(1672) [2], which is well established in experiments. (ii) The newly observed Ω(2012) resonance at Belle [15], which is interpreted as the first orbital excited state Ω(1 2 P 3/2 − ) [16,17]. (iii) The other first orbital excited state Ω(1 2 P 1/2 − ) whose mass is predicted to be ∼ 1950 MeV within the Lattice QCD [13] and the relativized quark models [5,6].…”

“…where ψ σ NLM L (ρ, λ) is the spatial wave function, which can be determined by solving the Schrödinger equation; σ = s, ρ, λ, a denotes the representation of the S 3 group. [2,15] and the theory predictions [3, 5-8, 12, 13] are also listed. Recently, the quantum number of the resonances Ω(2012) [15] and Ω(2250) [2] are not determined.…”

“…[2,15] and the theory predictions [3, 5-8, 12, 13] are also listed. Recently, the quantum number of the resonances Ω(2012) [15] and Ω(2250) [2] are not determined. According the Ref.…”

“…Fortunately, the Belle II experiments can offer a great opportunity for our study of the Ω spectrum. In 2018, the Belle Collaboration reported a new resonance denoted by Ω(2012) [15], a candidate of excited Ω state decaying into Ξ 0 K − and Ξ − K 0 s with a mass of M = 2012.4 ± 0.7(stat.) ± 0.6(syst.)…”