Observation of the doubly strange $b$ baryon $Omega_b^- $

Abstract

We report the observation of the doubly strange b baryon Omega_b- in the decay channel Omega_b- to J/psi Omega-, with J/psi to mu_s16 mu- and Omega- to Lambda K-, in $pbar{p}$ collisions at $sqrt{s}=1.96$ TeV. Using approximately 1.3 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron Collider, we observe 17.8 _s16/- 4.9 (stat) _s16/- 0.8 (syst) Omega_b- signal events at a mass of 6.165 _s16/- 0.010 (stat) _s16/- 0.013(syst.) GeV. The significance of the observed signal is 5.4 sigma, corresponding to a probability of 6.7 x 10^{-8} of it arising from a background fluctuation.