Measurement of electroweak production of two jets in association with a Z boson in proton-proton collisions at sqrt(s)= 8 TeV

TL;DR

This paper reports a measurement of the electroweak production cross section of two jets with a Z boson in proton-proton collisions at 8 TeV, confirming consistency with the Standard Model predictions.

Contribution

It provides the first measurement of the electroweak Z+2 jets production cross section at 8 TeV using CMS data, with detailed analysis of jet activity and phase space.

Findings

Measured electroweak Z+2 jets cross section: 174 +/- 15 (stat) +/- 40 (syst) fb

Results agree with Standard Model predictions

Jet activity analysis matches QCD expectations

Abstract

The purely electroweak (EW) cross section for the production of two jets in association with a Z boson, in proton-proton collisions at sqrt(s) = 8 TeV, is measured using data recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The electroweak cross section for the lljj final state (with l = e or mu and j representing the quarks produced in the hard interaction) in the kinematic region defined by M[ll] > 50 GeV, M[jj] > 120 GeV, transverse momentum pt[j] > 25 GeV, and pseudorapidity abs(eta[j]) < 5, is found to be sigma[EW](lljj) = 174 +/- 15 (stat) +/- 40 (syst) fb, in agreement with the standard model prediction. The associated jet activity of the selected events is studied, in particular in a signal-enriched region of phase space, and the measurements are found to be in agreement with QCD predictions.