Measurement of the $b$ Jet Cross Section in Events with a $Z$ Boson in $p\bar{p}$ Collisions at $\sqrt{s}$=1.96 TeV

TL;DR

This paper reports a measurement of the bottom jet production rate in events with a Z boson in proton-antiproton collisions at 1.96 TeV, comparing results with next-to-leading order QCD predictions.

Contribution

First measurement of the inclusive b jet cross section in Z boson events at Tevatron energies, using secondary vertex tagging for b jet identification.

Findings

Measured cross section times branching ratio: 0.93 ± 0.36 pb.

B-jet to total jet ratio: 2.36 ± 0.92%.

Results agree with NLO QCD predictions within uncertainties.

Abstract

A measurement of the inclusive bottom jet cross section is presented for events containing a $Z$ boson in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using the Collider Detector at Fermilab. $Z$ bosons are identified in their electron and muon decay modes, and $b$ jets with $E_T>20$ GeV and $|\eta|<1.5$ are identified by reconstructing a secondary decay vertex. The measurement is based on an integrated luminosity of about 330 ${\rm pb}^{-1}$. A cross section times branching ratio of $\sigma (Z+b {\rm jets}) \times {\cal B}(Z \to \ell^+ \ell^-)= 0.93 \pm 0.36$ pb is found, where ${\cal B}(Z\to \ell^+ \ell^-)$ is the branching ratio of the $Z$ boson or $\gamma^*$ into a single flavor dilepton pair ($e$ or $\mu$) in the mass range between 66 and 116 GeV$/c^2$. The ratio of $b$ jets to the total number of jets of any flavor in the $Z$ sample, within the same kinematic range as the $b$ jets, is $2.36 \pm 0.92%$. Here, the uncertainties are the quadratic sum of statistical and systematic uncertainties. Predictions made with NLO QCD agree, within experimental and theoretical uncertainties, with these measurements.