Measurement of t t-bar production with additional jet activity, including b quark jets, in the dilepton channel using pp collisions at sqrt(s) = 8 TeV

TL;DR

This paper measures top quark pair production with extra jets, including b jets, in proton-proton collisions at 8 TeV, providing detailed cross sections and comparing results with theoretical predictions.

Contribution

It presents the first measurements of differential cross sections for tt̄b and tt̄b b̄ production as functions of b jet kinematics in dilepton channels at 8 TeV.

Findings

Data agree with QCD predictions within uncertainties.

First measurement of tt̄b and tt̄b b̄ cross sections as functions of b jet properties.

Provides detailed jet multiplicity distributions in top pair events.

Abstract

Jet multiplicity distributions in top quark pair (t t-bar) events are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC using a data set corresponding to an integrated luminosity of 19.7 inverse femtobarns. The measurement is performed in the dilepton decay channels (e+ e-, mu+ mu-, and e+/- mu-/+). The absolute and normalized differential cross sections for t t-bar production are measured as a function of the jet multiplicity in the event for different jet transverse momentum thresholds and the kinematic properties of the leading additional jets. The differential t t-bar b and t t-bar b b-bar cross sections are presented for the first time as a function of the kinematic properties of the leading additional b jets. Furthermore, the fraction of events without additional jets above a threshold is measured as a function of the transverse momenta of the leading additional jets and the scalar sum of the transverse momenta of all additional jets. The data are compared and found to be consistent with predictions from several perturbative quantum chromodynamics event generators and a next-to-leading order calculation.