Measurement of Single W Production and Triple Gauge Boson Couplings in E+e- Collisions at S PDF Download

Author: Marco Verzocchi
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Languages : en
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Author: Yoshi Uchida
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Languages : en
Pages : 104

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W-Pair and Single-W production events are observed at LEP, the Large Electron Positron collider at CERN, using the L3 detector. All decay channels are considered, and data taken in the years 1998 and 1999, with electron-positron collision centre-of-mass energies from 189 GeV to 202 GeV are analysed. The integrated luminosity of the analysed data corresponds to approximately 400pb-1, and a total of approximately 5000 W-pair events and 100 single-W events are selected. The observed cross sections of these W production processes and the differential distributions of the event shapes are then used to measure the couplings of Wbosons with Z bosons and photons. Emphasis is placed on the unambiguous and efficient combination of the information from the different production and decay channels. For the couplings in the model in which gauge invariance is realised linearly, the following results are obtained ... where the errors shown are statistical, systematic and theoretical respectively. All results show consistency with expectations from the Standard Model.

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Languages : en
Pages : 8

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The standard model (SM) of particle physics has been extensively tested in the past three decades and is found to be in excellent agreement with experimental observations. It is widely assumed, however, that the SM is only a low energy approximation of a more general theory. Therefore, any significant deviation from the SM predictions yields information on the nature of a more fundamental theory. Production of WZ pairs is the least studied diboson process within the SM, as it is a charged final state and can only be produced at hadron colliders. A detailed study of this process probes the electroweak sector of the SM. In addition, searches for new phenomena in the production of heavy gauge boson pairs are interesting, as many extensions of the SM predict 1-4 additional heavy gauge bosons that can decay into a WZ boson pairs.

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Languages : en
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This study presents measurements of W±Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and muons. The data were collected in 2012 by the ATLAS experiment at the Large Hadron Collider and correspond to an integrated luminosity of 20.3 fb-1. The measured inclusive cross section in the detector fiducial region is ?W±Z→l'?ll = 35.1 ± 0.9(stat) ± 0.8(sys) ± 0.8(lumi) fb, for one leptonic decay channel. In comparison, the next-to-leading-order Standard Model expectation is 30.0 ± 2.1 fb. Cross sections for W+Z and W-Z production and their ratio are presented as well as differential cross sections for several kinematic observables. Limits on anomalous triple gauge boson couplings are derived from the transverse mass spectrum of the W±Z system. From the analysis of events with a W and a Z boson associated with two or more forward jets an upper limit at 95% confidence level on the W±Z scattering cross section of 0.63 fb, for each leptonic decay channel, is established, while the Standard Model prediction at next-to-leading order is 0.13 ± 0.01 fb. Limits on anomalous quartic gauge boson couplings are also extracted.

Author:
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Languages : en
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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Languages : en
Pages : 81

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The production of W boson pairs in proton-proton collisions at √s = 8 TeV is studied using data corresponding to 20.3 fb-1 of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The W bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 WW candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the W branching fractions to leptons in order to obtain the total WW production cross section, which is found to be 71.1 ± 1.1(stat)-5.0+ 5.7(syst) ± 1.4(lumi) pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2-1.4+1.6(scale) ± 1.2(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. In conclusion, the distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.

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Languages : en
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The D0 and CDF Collaborations measure boson pair production including W[gamma], WW, WZ, ZZ and Z[gamma] production in p[anti p] collisions at[radical]s= 1800 GeV. New results, from direct measurements, are described including W[gamma], WW, and Z[gamma] production cross sections and limits on non-Standard Model triple gauge boson couplings. The limits on anomalous WW[gamma], WWZ, Z[gamma][gamma] and ZZ[gamma] couplings are the most restrictive available. Prospects for Run II are discussed.

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Languages : en
Pages : 40

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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. 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. The observed cross sections are compatible with the expectations of next-to-next-to-leading-order quantum chromodynamics. 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.

Author: Matthew Dobbs
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Languages : en
Pages :

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Author:
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ISBN:
Category :
Languages : en
Pages : 81

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Book Description
The production of W boson pairs in proton-proton collisions at √s = 8 TeV is studied using data corresponding to 20.3 fb–1 of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The W bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 WW candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the W branching fractions to leptons in order to obtain the total WW production cross section, which is found to be 71.1 ± 1.1(stat)–5.0+ 5.7(syst) ± 1.4(lumi) pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2–1.4+1.6(scale) ± 1.2(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. In conclusion, the distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.