# Observation of the Ωb- baryon and measurement of the properties of the Ξb- and Ωb- baryons

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http://hdl.handle.net/10138/24454

#### Citation

Aaltonen , T , Mehtala , P , Orava , R , Maki , T , Saarikko , H , Osterberg , K & CDF Collaboration 2009 , ' Observation of the Ωb- baryon and measurement of the properties of the Ξb- and Ωb- baryons ' , Physical Review D : Particles, Fields, Gravitation and Cosmology , vol. 80 , no. 7 , pp. 072003 . https://doi.org/10.1103/PhysRevD.80.072003

 Title: Observation of the Ωb- baryon and measurement of the properties of the Ξb- and Ωb- baryons Alternative title: Observation of the Omega_b^- and Measurement of the Properties of the Xi_b^- and Omega_b^- Author: Aaltonen, Timo; Mehtala, P.; Orava, R.; Maki, T.; Saarikko, H.; Osterberg, K.; CDF Collaboration Contributor organization: Helsinki Institute of PhysicsParticle Physics and Astrophysics Date: 2009 Language: eng Number of pages: 16 Belongs to series: Physical Review D : Particles, Fields, Gravitation and Cosmology ISSN: 1550-7998 DOI: https://doi.org/10.1103/PhysRevD.80.072003 URI: http://hdl.handle.net/10138/24454 Abstract: We report the observation of the bottom, doubly-strange baryon Omega^-_b through the decay chain Omega^-_b -> J/psi Omega^-, where J/psi -> mu^+ mu^-, Omega^- -> Lambda K^-, and Lambda -> p pi^-, using 4.2 fb^{-1} of data from p\bar p collisions at sqrt{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^{-8}, or 5.5 Gaussian standard deviations. The Omega^-_b mass is measured to be 6054.4 +/- 6.8 (stat.) +/- 0.9 (syst.) MeV/c^2. The lifetime of the Omega^-_b baryon is measured to be 1.13^{+0.53}_{-0.40}(stat.) +/- 0.02(syst.)\$ ps. In addition, for the \Xi^-_b baryon we measure a mass of 5790.9 +/- 2.6(stat.) +/- 0.8(syst.) MeV/c^2 and a lifetime of 1.56^{+0.27}_{-0.25}(stat.) +/-0.02(syst.) ps. Under the assumption that the \Xi_b^- and \Omega_b^- are produced with similar kinematic distributions to the \Lambda^0_b baryon, we find sigma(Xi_b^-) B(Xi_b^- -> J/psi Xi^-)}/ sigma(Lambda^0_b) B(Lambda^0_b -> J/psi Lambda)} = 0.167^{+0.037}_{-0.025}(stat.) +/-0.012(syst.) and sigma(Omega_b^-) B(Omega_b^- -> J/psi Omega^-)/ sigma(Lambda^0_b) B(Lambda^0_b -> J/psi Lambda)} = 0.045^{+0.017}_{-0.012}(stat.) +/- 0.004(syst.) for baryons produced with transverse momentum in the range of 6-20 GeV/c.We report the observation of the bottom, doubly-strange baryon Ωb- through the decay chain Ωb-→J/ψΩ-, where J/ψ→μ+μ-, Ω-→ΛK-, and Λ→pπ-, using 4.2  fb-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 4.0×10-8, or 5.5 Gaussian standard deviations. The Ωb- mass is measured to be 6054.4±6.8(stat)±0.9(syst)  MeV/c2. The lifetime of the Ωb- baryon is measured to be 1.13-0.40+0.53(stat)±0.02(syst)  ps. In addition, for the Ξb- baryon we measure a mass of 5790.9±2.6(stat)±0.8(syst)  MeV/c2 and a lifetime of 1.56-0.25+0.27(stat)±0.02(syst)  ps. Under the assumption that the Ξb- and Ωb- are produced with similar kinematic distributions to the Λb0 baryon, we find σ(Ξb-)B(Ξb-→J/ψΞ-)/σ(Λb0)B(Λb0→J/ψΛ)=0.167-0.025+0.037(stat)±0.012(syst) and σ(Ωb-)B(Ωb-→J/ψΩ-)/σ(Λb0)B(Λb0→J/ψΛ)=0.045-0.012+0.017(stat)± 0.004(syst) for baryons produced with transverse momentum in the range of 6–20  GeV/c. Description: 17 pages, 10 figures Subject: 114 Physical sciences hep-ex Peer reviewed: Yes Usage restriction: restrictedAccess
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