# Direct observation of the strange $b$ baryon $\Xi_b^{-}$

Abstract : We report the first direct observation of the strange b baryon Xi_b^{-}. We reconstruct the decay Xi_b^{-} to J/psi Xi^{-}, with J/psi to dimuons and Xi^{-} to Lambda pion, in ppbar collisions at sqrt(s) = 1.96 TeV. Using 1.3 fb^{-1} of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat.)+ 1.9/-0.4(syst.) Xi_b^{-} candidates at a mass of 5.774 +/- 0.011(stat.) +/- 0.015 (syst.) GeV. The significance of the observed signal is 5.5 sigmas, equivalent to a probability of 3.3 X 10^{-8} of it arising from a background fluctuation. Normalizing to the decay Lambda_b to J/psi Lambda, we measure the relative rate to be 0.28 +/- 0.09(stat.)+ 0.09/-0.08 (syst.).
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00154203
Contributor : Dominique Girod <>
Submitted on : Wednesday, June 13, 2007 - 8:49:46 AM
Last modification on : Tuesday, December 1, 2020 - 4:46:02 PM

### Citation

V.M. Abazov, B. Abbott, M. Abolins, B.S. Acharya, M. Adams, et al.. Direct observation of the strange $b$ baryon $\Xi_b^{-}$. Physical Review Letters, American Physical Society, 2007, 99, pp.052001. ⟨10.1103/PhysRevLett.99.052001⟩. ⟨in2p3-00154203⟩

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