Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector

ATLAS Collaboration

Abstract

A measurement of the ZZ production cross section in proton-proton collisions at sqrt(s) = 7 TeV using data recorded by the ATLAS experiment at the LHC is presented. In a data sample corresponding to an integrated luminosity of 1.02 fb^-1 collected in 2011, 12 events containing two Z boson candidates decaying to electrons and/or muons are observed. The expected background contribution is 0.3 +/- 0.3 (stat) ^{+0.4}_{-0.3} (syst.) events. The cross section measured in a phase-space region with good detector acceptance and for dilepton masses within the range 66 GeV to 116 GeV is sigma_{ZZ to ll ll}^{fid} = 19^{+6}_{-5} (stat.) +/- 1 (syst.) +/- 1 (lumi.) fb. This result is then used to derive the total cross section for on-shell ZZ production, sigma_{ZZ}^{tot}= 8.5^{+2.7}_{-2.3} (stat.)^{+0.4}_{-0.3} (syst.) +/- 0.3 (lumi.) pb, which is consistent with the Standard Model expectation of 6.5^{+0.3}_{-0.2} pb calculated at the next-to-leading order in QCD. Limits on anomalous neutral triple gauge boson couplings are derived.

Measurement of the ZZ production cross section and limits on anomalous neutral triple gauge couplings in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector

Abstract

A measurement of the ZZ production cross section in proton-proton collisions at sqrt(s) = 7 TeV using data recorded by the ATLAS experiment at the LHC is presented. In a data sample corresponding to an integrated luminosity of 1.02 fb^-1 collected in 2011, 12 events containing two Z boson candidates decaying to electrons and/or muons are observed. The expected background contribution is 0.3 +/- 0.3 (stat) ^{+0.4}_{-0.3} (syst.) events. The cross section measured in a phase-space region with good detector acceptance and for dilepton masses within the range 66 GeV to 116 GeV is sigma_{ZZ to ll ll}^{fid} = 19^{+6}_{-5} (stat.) +/- 1 (syst.) +/- 1 (lumi.) fb. This result is then used to derive the total cross section for on-shell ZZ production, sigma_{ZZ}^{tot}= 8.5^{+2.7}_{-2.3} (stat.)^{+0.4}_{-0.3} (syst.) +/- 0.3 (lumi.) pb, which is consistent with the Standard Model expectation of 6.5^{+0.3}_{-0.2} pb calculated at the next-to-leading order in QCD. Limits on anomalous neutral triple gauge boson couplings are derived.

Paper Structure

This paper contains 3 equations, 2 figures, 2 tables.

Figures (2)

  • Figure 1: The mass of the leading lepton pair versus the mass of the subleading lepton pair. The events observed in the data are shown as solid circles and the $ZZ$ signal prediction from simulation as boxes. The large dashed box indicates the signal region defined by the requirements on the lepton-pair masses.
  • Figure 2: (a) Transverse momentum $p_{\mathrm{T}}^{ZZ\xspace}$ and (b) invariant mass $M_{ZZ\xspace}$ of the four-lepton system for the selected events. The points represent the observed data and the histograms show the signal prediction from simulation. The shaded band on each histogram shows the combined statistical and systematic uncertainty on the signal prediction. The predicted number of background events from the data-driven background estimate is indicated on the plot.