Observation of Z Decays to b Quark Pairs at the Tevatron Collider

TL;DR

This paper reports the first observation of Z boson decays into b-quark pairs at the Tevatron, using advanced selection and analysis techniques to identify and measure the decay signal amidst background processes.

Contribution

It presents the first evidence of Z -> bb decays at the Tevatron, employing a novel analysis method with secondary vertex identification and kinematic discrimination.

Findings

3.23 sigma excess over background prediction

91+-30+-19 Z -> bb decay events observed

Results consistent with Standard Model expectations

Abstract

A search for Z boson decays to pairs of b-quark jets has been performed in the full dataset collected with the CDF detector at the Tevatron proton-antiproton collider. After the selection of a pure sample of bb events by means of the identification of secondary vertices from b-quark decays, we have used two kinematic variables to further discriminate the electroweak bb production from QCD processes, and sought evidence for the Z decay in the dijet invariant mass distribution. An absolute background prediction allows the extraction of an excess of events inconsistent with the background predictions by 3.23 sigma but in good agreement with the amount and characteristics of the expected signal. We then fit the mass distribution with an unbinned likelihood technique, and obtain a Z -> bb signal amounting to 91+-30+-19 events.