Date of Award
Doctor of Philosophy (PhD)
We present the first observation of the weak decay Ξ−b → Λ0b π−, which is mediated by an s → u ̄ud transitionwithin the Ξ_b^- baryon. The analysis uses a pp collision data sample at a center-of-mass energy of 13 TeV corresponding to 5.5 fb^(−1) of integrated luminosity. The sample of Λb0 baryons used in this analysis are reconstructed through their decays to Λ+c π− and Λ+c π−π+π−. From a fit to the Ξ−b → Λ0b π− mass spectrum, the Ξ−b → Λ0b π− decay is observed with a significance of 11.3 standard deviations, thus establishing observation of this decay. The relative branching fraction is measured to be f(Ξ−b)/f(Λ0b)*B(Ξ−b → Λ0b π−) = (6.35 ± 0.70 ± 0.47) × 10^(−4), where f(Ξ−b) and f(Λ0b) are the fragmentation fractions, and B(Ξ−b → Λ0b π−) is the branching fraction, and the uncertainties are statistical and experimental systematic. Using the measured value of f(Ξ−b)/f(Λ0b)= (8.2 ± 0.7 ± 0.6 ± 2.5) × 10^(−2), the branching fraction is measured as B(Ξ−b → Λ0b π−) = (0.77 ± 0.11 ± 0.07 ± 0.23) × 10^(−2). For predictions of Ξ−b decay width that only considers b-quark decay, this contribution must be added, thus increasing predictions of the Ξ−b decay width by about 1%
Li, Zhuoming, "Observation of the Ξ_b^-→Λ_b^0 π^- decay and measurement of B(Ξ_b^-→Λ_b^0 π^-)" (2022). Dissertations - ALL. 1589.