Measurement of Rb at SLD

TL;DR

This paper presents a precise measurement of the ratio Rb, representing Z boson decays to bottom quarks, using advanced vertex detection and a large data sample from the SLD experiment.

Contribution

It introduces a double tag technique based on topological vertex reconstruction, achieving high b-tagging efficiency and purity, reducing systematic uncertainties in Rb measurement.

Findings

Measured Rb = 0.2176 ± 0.0033 (stat) ± 0.0017 (syst) ± 0.0008 (Rc)

High b-tagging efficiency of 37% with 97.2% purity

Reduced charm contamination and correlation systematics

Abstract

We report a new measurement of Rb=Gamma(Z -> bb)/ Gamma(Z -> hadrons) using a double tag technique where the b selection is based on topological reconstruction of the mass of the B-decay vertex. The measurement was performed using a sample of 150k hadronic Z0 events collected with the SLD at the SLAC Linear Collider during the years 1993-1995. The method utilizes the 3-D vertexing abilities of the SLD CCD pixel vertex detector and the small stable SLC beams to obtain a high b tagging efficiency of 37% for a purity of 97.2%. The high purity reduces the systematics introduced by charm contamination and correlations with Rc. We obtain a result of Rb=0.2176+/-0.0033(stat.)+/-0.0017(syst.)+/-0.0008(Rc). (Presented at the XXXIst Rencontres de Moriond Electroweak Interactions and Unified Theories, Les Arcs, Savoie, France, March 16-23, 1996.)