Measurement of Vub using b hadron semileptonic decays

TL;DR

This paper measures the CKM matrix element Vub by analyzing inclusive charmless semileptonic decays of b hadrons using OPAL data, providing a new experimental determination with quantified uncertainties.

Contribution

It presents the first measurement of Vub from OPAL data using b -> Xu l event topology, including detailed error analysis and theoretical uncertainties.

Findings

Measured Br(b -> Xu l) as (1.63 +/- 0.53 +0.55/-0.62) x 10^(-3)

Determined |Vub| = (4.00 +/- 0.65(stat) +0.67/-0.76(sys) +/- 0.19(HQE)) x 10^(-3)

Quantified uncertainties from statistics, systematics, and theory.

Abstract

The magnitude of the CKM matrix element Vub is determined by measuring the inclusive charmless semileptonic branching fraction of beauty hadrons at OPAL based on b -> Xu l nu event topology and kinematics. This analysis uses OPAL data collected between 1991 and 1995, which correspond to about four million hadronic Z decays. We measure Br(b -> Xu l) to be (1.63 +/- 0.53 +0.55/-0.62) x 10^(-3). The first uncertainty is the statistical error and the second is the systematic error. From this analysis, Vub is determined to be: |Vub| = (4.00 +/- 0.65(stat) +0.67/-0.76(sys) +/- 0.19(HQE)) x 10^(-3). The last error represents the theoretical uncertainties related to the extraction of |Vub| from Br(b -> Xu l) using the Heavy Quark Expansion.