Observation of New Heavy Baryon Ξb

Dmitry Litvintsev, Patrick Lukens
(Fermilab)

Phys. Rev. Lett. 99, 052002 (2007)

This web page summarizes results of a search for new heavy baryon Ξb composed of b,s,d quarks. The search is based on data comprising 1.9 fb-1 of integrated luminosity. Using fully reconstructed decay

Ξb- → J/Ψ Ξ-;     J/Ψ → μ+μ-;     Ξ- → Λ0 π-;     Λ0→p π -    
 
we measure:

Statistical significance of the &Xib signal is over 7 standard deviations.



GIF EPS



GIF EPS (toggle "a" in "gv" viewer to get proper hatch style)

Major points of the analysis

  • To reduce background and improve secondary vertex precision we use tracks reconstructed in Silicon Vertex Detector (SVX) from hits left by long lived Ξ hyperons.
  • Utilization of Ξ-track turns 5-track final state (μμπpπ) into 3-track vertex (μμΞ), which is similar to B+ → J/ψ K+ (μμK) in vertex topology and kinematics.
  • Selection criteria are data driven and independent of the signal under study:
    • Cuts are optimized to get the best B+ → J/ψ K+ signal
    • The same cuts applied to Ξb- → J/ψ Ξ - candidates
  • This strategy was used in CDF Bc+ → J/ψ π+ observation

Plots