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Observation of the Ωb−\Omega_b^- and Measurement of the Properties of the Ξb−\Xi_b^- and Ωb−\Omega_b^-

Collaboration
May, 2009
17 pages
Published in:
  • Phys.Rev.D 80 (2009) 072003
e-Print:
DOI:
Report number:
  • FERMILAB-PUB-09-256-E
Experiments:
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2009201320172021202405101520
Abstract: (arXiv)
We report the observation of the bottom, doubly-strange baryon Ωb−\Omega^-_b through the decay chain Ωb−→J/ψ Ω−\Omega^-_b \rightarrow J/\psi \, \Omega^-, where J/ψ→μ+ μ−J/\psi \rightarrow \mu^+\, \mu^-, Ω−→Λ K−\Omega^- \rightarrow \Lambda \, K^-, and Λ→p π−\Lambda \rightarrow p \, \pi^-, using 4.2 fb−1^{-1} of data from ppˉp\bar p collisions at s=1.96\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 4.0×10−84.0 \times 10^{-8}, or 5.5 Gaussian standard deviations. The Ωb−\Omega^-_b mass is measured to be 6054.4±6.8(stat.)±0.9(syst.)6054.4\pm 6.8 (\textrm{stat.})\pm 0.9 (\textrm{syst.}) MeV/c2c^2. The lifetime of the Ωb−\Omega^-_b baryon is measured to be 1.13−0.40+0.53(stat.)±0.02(syst.)1.13^{+0.53}_{-0.40}(\textrm{stat.})\pm0.02(\textrm{syst.}) ps. In addition, for the Ξb−\Xi^-_b baryon we measure a mass of 5790.9±2.6(stat.)±0.8(syst.)5790.9\pm2.6(\textrm{stat.})\pm0.8(\textrm{syst.}) MeV/c2c^2 and a lifetime of 1.56−0.25+0.27(stat.)±0.02(syst.)1.56^{+0.27}_{-0.25}(\textrm{stat.})\pm0.02(\textrm{syst.}) ps. %These measurements were performed using 4.2 fb−1^{-1} of %data from ppˉp\bar p collisions at s=1.96\sqrt{s}=1.96 TeV, and %recorded with the Collider Detector at Fermilab. Under the assumption that the Ξb−\Xi_b^- and Ωb−\Omega_b^- are produced with similar kinematic distributions to the Λb0\Lambda^0_b baryon, we find σ(Ξb−)B(Ξb−→J/ψ Ξ−)σ(Λb0)B(Λb0→J/ψ Λ)=0.167−0.025+0.037(stat.)±0.012(syst.)\frac{\sigma(\Xi_b^-){\cal B}(\Xi_b^- \rightarrow J/\psi \, \Xi^-)} {\sigma(\Lambda^0_b){\cal B}(\Lambda^0_b \rightarrow J/\psi \, \Lambda)} = 0.167^{+0.037}_{-0.025}(\textrm{stat.})\pm0.012(\textrm{syst.}) and σ(Ωb−)B(Ωb−→J/ψ Ω−)σ(Λb0)B(Λb0→J/ψ Λ)=0.045−0.012+0.017(stat.)±0.004(syst.)\frac{\sigma(\Omega_b^-){\cal B}(\Omega_b^- \rightarrow J/\psi \, \Omega^-)} {\sigma(\Lambda^0_b){\cal B}(\Lambda^0_b \rightarrow J/\psi \, \Lambda)} = 0.045^{+0.017}_{-0.012}(\textrm{stat.})\pm0.004(\textrm{syst.}) for baryons produced with transverse momentum in the range of 6 − 206 \, - \, 20 GeV/cc.
Note:
  • 17 pages, 10 figures
  • 13.60.Rj
  • 14.20.Mr
  • 13.30.Eg
  • OSG : CDF
  • Omega/b: hadronic decay
  • J/psi(3100): leptonic decay
  • baryon: transverse momentum
  • anti-p p: interaction
  • Omega/b: mass
  • Omega/b: lifetime