Evidence for the Strangeness-Changing Weak Decay Ξ_{b}^{-}→Λ_{b}^{0}π^{-}

Area of Science:

• Particle Physics
• High Energy Physics
• Quantum Chromodynamics

Background:

• The Standard Model of particle physics describes fundamental particles and forces.
• Baryon decays provide crucial tests of the Standard Model.
• Strangeness-changing weak decays are rare processes offering unique insights.

Purpose of the Study:

• To perform the first search for the strangeness-changing weak decay Ξ_{b}^{-}→Λ_{b}^{0}π^{-}.
• To measure the relative rate and branching fraction of this decay.
• To contribute to the understanding of b hadron decays.

Main Methods:

• Analysis of pp collision data collected by the LHCb detector.
• Utilizing an integrated luminosity of 3.0 fb^{-1}.
• Statistical analysis to establish the significance of the observed signal.

Main Results:

• Observation of the Ξ_{b}^{-}→Λ_{b}^{0}π^{-} decay with a significance of 3.2 standard deviations.
• Measurement of the relative rate f_{Ξ_{b}^{-}}/f_{Λ_{b}^{0}}B(Ξ_{b}^{-}→Λ_{b}^{0}π^{-}) = (5.7±1.8_{-0.9}^{+0.8})×10^{-4}.
• Estimated branching fraction B(Ξ_{b}^{-}→Λ_{b}^{0}π^{-}) between (0.57±0.21)% and (0.19±0.07)%.

Conclusions:

• The first evidence for the strangeness-changing weak decay Ξ_{b}^{-}→Λ_{b}^{0}π^{-} has been established.
• The measured branching fraction provides a new data point for testing theoretical models of b baryon decays.
• This discovery opens new avenues for exploring rare B baryon transitions.