Measurement of the Properties of the Λb, Ξb0, Ξb-, and Ωb-

Patrick Lukens
Fermilab

CDF observes b-baryons through the following decay chains:

Λb → J/ψ Λ, J/ψ → μ+μ-, Λ → p π-.
Ξb- → J/ψ Ξ-, J/ψ → μ+μ-, Ξ- → Λ π-, Λ → p π-.
Ωb- → J/ψ Ω-, J/ψ → μ+μ-, Ω- → Λ K-, Λ → p π-.
Ξb- → Ξc0 π-, Ξc0 → Ξ- π+, Ξ- → Λ π-, Λ → p π-.
Ξb0 → Ξc+ π-, Ξc+ → Ξ- π+ π+, Ξ- → Λ π-, Λ → p π-.

In addition, evidence is presented for the first observation of the process
Ωb- → Ωc0 π-, Ωc0 → Ω- π+, Ω- → Λ K-, Λ → p π-.

Ξ- π+ and Ξ- π+ π+ mass distributions. Red overlay is a projection of the unbinned likelihood fit.

J/ψ - hyperon mass distributions. Projections of the unbinned fits to the mass distributions are overlaid in dashed lines.


Charmed hyperon - π- mass distributions. Projections of the unbinned fits to the mass distributions are overlaid in dashed lines.

The data was collected in 9.6 fb-1 of collisions. The properties of the baryons are measured as follows:


Mass (MeV/c2) Mean Life (ps)
Ξ0c 2470.85 ± 0.24 ± 0.55
-
Ξ+c 2468.00 ± 0.18 ± 0.51
-
Λb 5620.15 ± 0.31 ± 0.47
1.565 ± 0.035 ± 0.020
Ξ-b 5793.4 ± 1.8 ± 0.7
1.32 ± 0.14 ± 0.02
Ξ0b 5788.7 ± 4.3 ± 1.4
-
Ω-b 6047.5 ± 3.8 ± 0.6
1.66 +0.53-0.40 ± 0.02

In addition, the isospin splittings of the Ξc and Ξb systems are measured as follows:


Mass Difference (MeV/c2)
M(Ξ0c) - M(Ξ+c) 2.85 ± 0.30 ± 0.04
M(Ξ-b) - M(Ξ0b) 4.7 ± 4.7 ± 0.7

Reference signal plots Baryon signal plots A public note is available here

The paper submitted to arXiv is available here
Figures from the paper:
Fig. 1a Fig. 1b Fig. 1c
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