Observation of the Ω-b
of the Properties of the Ξ-b and Ω-b
CDF observes the production of the Ω-b
through the decay chain Ω-b
→ J/ψ Ω-, J/ψ →
K-, Λ → p π-. The data
was collected in 4.2 fb-1 of collisions.
An illustration of the decay chain
J/ψ Ξ- and J/ψ
The properties of the Ξ-b
are measured within a
comprehensive program of b-hadron
studies, which provide a control
sample for the understanding of the systematic effects that are
important to the measurements. The following properties have been
± 2.6 ± 0.8
± 6.8 ± 0.9
The mass measurement of the Ξ-b
our previous measurement, made with a 1.9 fb-1 data sample1.
The lifetime measurement of the Ξ-b
the first ever made with a fully reconstructed final state.
The mass measurement of the Ω-b
is inconsistent with the only
previous observation of this particle2. The lifetime
measurement of the Ω-b is the first ever obtained.
A comparison between the mass measurements and several theoretical
predicitions is summarized below:
The relative rates of production of the two particles are measured with
respect to the Λb, since it is the only b-baryon for which a large sample
is available. The measurement is made with the assumption that
the production kinematics of the Ξ-b
and Ω-b are
identical to that of the Λb. The ratios of cross
section times branching fractions are
Details can be obtained from a recent seminar and the paper in the
Joint Experimental-Theoretical Seminar (19 May 2009)
Paper available at
1. T. Aaltonen et al.
(CDF Collaboration), Phys. Rev. Lett. 99,
2. V. M. Abazov et. al.
(D0 Collaboration), Phys. Rev. Lett. 101,