Measurement of the cross section ratio sigma(t t-bar b b-bar) / sigma(t t-bar jj) in pp collisions at sqrt(s) = 8 TeV

TL;DR

This paper reports the first measurement of the ratio of top-antitop bottom-antibottom to top-antitop jet-jet production cross sections in proton-proton collisions at 8 TeV, using CMS data, and compares it with QCD predictions.

Contribution

It provides the first experimental measurement of the cross section ratio sigma(t t-bar b b-bar) / sigma(t t-bar jj) at 8 TeV, including absolute cross sections and comparison with theoretical calculations.

Findings

Measured ratio for pt > 20 GeV is 0.022 +/- 0.003 (stat) +/- 0.005 (syst).

Measured ratio for pt > 40 GeV is compatible with NLO QCD calculations.

Absolute cross sections for sigma(t t-bar b b-bar) and sigma(t t-bar jj) are also reported.

Abstract

The first measurement of the cross section ratio sigma(t t-bar b b-bar) / sigma(t t-bar jj) is presented using a data sample corresponding to an integrated luminosity of 19.6 inverse femtobarns collected in pp collisions at sqrt(s) = 8 TeV with the CMS detector at the LHC. Events with two leptons (e or mu) and four reconstructed jets, including two identified as b quark jets, in the final state are selected. The ratio is determined for a minimum jet transverse momentum pt of both 20 and 40 GeV. The measured ratio is 0.022 +/- 0.003 (stat) +/- 0.005 (syst) for pt > 20 GeV. The absolute cross sections sigma(t t-bar b b-bar) and sigma(t t-bar jj) are also measured. The measured ratio for pt > 40 GeV is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.