Observation of the Omega [subscript b][superscript -] baryon and measurement of the properties of the Xi[subscript b][superscript -] and Omega [subscript b][superscript -] baryons

Abstract

We report the observation of the bottom, doubly-strange baryon Ω[subscript b][superscript -] through the decay chain Ω[subscript b][superscript -]→J/ψΩ[superscript -], where J/ψ→μ[superscript +]μ[superscript -], Ω[superscript -]→ΛK[superscript -], and Λ→pπ[superscript -], using 4.2 fb[superscript -1] of data from pp̅ collisions at √s=1.96 TeV, and recorded with the Collider Detector at Fermilab. A signal is observed whose probability of arising from a background fluctuation is 4.0×10[superscript -8], or 5.5 Gaussian standard deviations. The Ω[subscript b][superscript -] mass is measured to be 6054.4±6.8(stat)±0.9(syst) MeV/c[superscript 2]. The lifetime of the Ω[subscript b][superscript -] baryon is measured to be 1.13[subscript -0.40][superscript +0.53](stat)±0.02(syst) ps. In addition, for the Ξ[subscript b][superscript -] baryon we measure a mass of 5790.9±2.6(stat)±0.8(syst) MeV/c[superscript 2] and a lifetime of 1.56[subscript -0.25][superscript +0.27](stat)±0.02(syst) ps. Under the assumption that the Ξ[subscript b][superscript -] and Ω[subscript b][superscript -] are produced with similar kinematic distributions to the Λ[subscript b][superscript 0] baryon, we find σ(Ξ[subscript b][superscript -])B(Ξ[subscript b][superscript -]→J/ψΞ[superscript ]-)/σ(Λ[subscript b][superscript 0])B(Λ[subscript b][superscript 0]→J/ψΛ)=0.167[subscript -0.025][superscript +0.037](stat)±0.012(syst) and σ(Ω[subscript b][superscript -])B(Ω[subscript b][superscript -]→J/ψΩ[superscript -])/σ(Λ[subscript b][superscript -])B(Λ[subscript b][superscript -]→J/ψΛ)=0.045[subscript -0.012][superscript +0.017](stat)± 0.004(syst) for baryons produced with transverse momentum in the range of 6–20 GeV/c.