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.
Highlights
Background to theZZ signal originates from events with a Z boson decaying to leptons plus additional jets or photons (W=Z þ X), from top-quark production and from other diboson final states
The resulting total cross section for on-shell ZZ production, tZoZt 1⁄4 8:5þÀ22::73ðstatÞþÀ00::43ðsystÞ Æ 0:3ðlumiÞ pb, is consistent with the standard model expectation of 6:5þÀ00::32 pb calculated at the next-to-leading order in QCD
Background to the ZZ signal originates from events with a Z boson decaying to leptons plus additional jets or photons (W=Z þ X), from top-quark production and from other diboson final states
Summary
Background to theZZ signal originates from events with a Z (or WÆ) boson decaying to leptons plus additional jets or photons (W=Z þ X), from top-quark production and from other diboson final states. The resulting total cross section for on-shell ZZ production, tZoZt 1⁄4 8:5þÀ22::73ðstatÞþÀ00::43ðsystÞ Æ 0:3ðlumiÞ pb, is consistent with the standard model expectation of 6:5þÀ00::32 pb calculated at the next-to-leading order in QCD.
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