Limits on the Anomalous ZZ and Z Gamma Couplings in Panti P Collisions at Radicals PDF Download

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Pages : 8

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Pages : 9

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The authors performed a direct search for the anomalous ZZ? and Z?? couplings by studying p{anti p} → ll? + X, (l = e,?) events at √s = 1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 14.3 pb−1 (13.7 pb−1) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZ? couplings: {vert_bar}h30{sup Z}{vert_bar}

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The authors performed a direct search for the anomalous ZZ[gamma] and Z[gamma][gamma] couplings by studying p[anti p][yields][ell][ell][gamma]+ X, ([ell]= e, [mu]) events at[radical]s= 1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 14.3 pb[sup[minus]1] (13.7 pb[sup[minus]1]) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZ[gamma] couplings:[vert-bar]h[sub 30][sup Z][vert-bar]

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Pages : 7

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The authors present a measurement of the Z[gamma] production cross section and limits on anomalous ZZ[gamma] and Z[gamma][gamma] couplings for form-factor scales of [Lambda] = 750 and 1000 GeV. The measurement is based on 138 (152) candidate events in the ee[gamma] ([mu][mu][gamma]) final state using 320 (290) pb−1 of p{bar p} collisions at √s = 1.96 TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are

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We present the first observation of the Z? →?{bar?}? process at the Tevatron at 5.1 standard deviations significance, based on 3.6 fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p{bar p} Collider at √s = 1.96 TeV. The measured Z? cross section multiplied by the branching fraction of Z → {nu}{bar {nu}} is 32 ± 9(stat. + syst.) ± 2(lumi.) fb for the photon E{sub T}> 90 GeV. It is in agreement with the standard model prediction of 39 ± 4 fb. We set the most restrictive limits on anomalous trilinear Z?? and ZZ? gauge boson couplings at a hadron collider to date, with three constraints being the world's strongest.

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The production of Z bosons with one or two isolated high-energy photons is studied using pp collisions at √s=8 TeV. The analyses use a data sample with an integrated luminosity of 20.3 fb-1 collected by the ATLAS detector during the 2012 LHC data taking. The Z? and Z?? production cross sections are measured with leptonic (e+e-, ?+?-, ?????????) decays of the Z boson, in extended fiducial regions defined in terms of the lepton and photon acceptance. They are then compared to cross-section predictions from the Standard Model, where the sources of the photons are radiation off initial-state quarks and radiative Z-boson decay to charged leptons, and from fragmentation of final-state quarks and gluons into photons. The yields of events with photon transverse energy ET > 250 GeV from l+l-? events and with ET > 400 GeV from ?????????? events are used to search for anomalous triple gauge-boson couplings ZZ? and Z??. The yields of events with diphoton invariant mass m?? > 200 GeV from l+l-?? events and with m?? > 300 GeV from ??????????? events are used to search for anomalous quartic gauge-boson couplings ZZ?? and Z???. As a result, no deviations from Standard Model predictions are observed and limits are placed on parameters used to describe anomalous triple and quartic gauge-boson couplings.

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Pages : 23

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A measurement of the inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton–proton collisions at √s = 8 TeV are presented. The analysis is based on a data sample, corresponding to an integrated luminosity of 19.6 fb−1, collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes ZZ → lll'l', where l = e,? and l' = e,?,?. The measured total cross section ?(pp → ZZ) = 7.7 ± 0.5 (stat)-0.4+0.5 (syst) ± 0.4 (theo) ± 0.2 (lumi) pb, for both Z bosons produced in the mass range 60 msubZ/sub 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. As a result, the invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ? couplings at the 95% confidence level: –0.004 fsub4/subsupZ/sup 0.004, –0.004 fsub5/subsupZ/sup 0.004, –0.005 fsub4

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Pages : 40

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The cross section for the production of Z? in proton-proton collisions at 8 TeV is measured based on data collected by the CMS experiment at the LHC corresponding to an integrated luminosity of 19.5 fb-1. Events with an oppositely-charged pair of muons or electrons together with an isolated photon are selected. Furthermore, the differential cross section as a function of the photon transverse momentum is measured inclusively and exclusively, where the exclusive selection applies a veto on central jets. These observed cross sections are compatible with the expectations of next-to-next-to-leading-order quantum chromodynamics. As a result, limits on anomalous triple gauge couplings of ZZ? and Z?? are set that improve on previous experimental results obtained with the charged lepton decay modes of the Z boson.

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Pages : 39

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The cross section for the production of Z[gamma] in proton-proton collisions at 8 TeV is measured based on data collected by the CMS experiment at the LHC corresponding to an integrated luminosity of 19.5 fb-1. Events with an oppositely-charged pair of muons or electrons together with an isolated photon are selected. Furthermore, the differential cross section as a function of the photon transverse momentum is measured inclusively and exclusively, where the exclusive selection applies a veto on central jets. These observed cross sections are compatible with the expectations of next-to-next-to-leading-order quantum chromodynamics. As a result, limits on anomalous triple gauge couplings of ZZ[gamma] and Z[gamma][gamma] are set that improve on previous experimental results obtained with the charged lepton decay modes of the Z boson.