Measurement of the Tau-pair Cross Section and Charge Asymmetry at the Z Degree Resonance PDF Download

Author: Martin Werner Grunewald
Publisher:
ISBN:
Category :
Languages : en
Pages : 532

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Author: Martin Werner Grünewald
Publisher:
ISBN:
Category :
Languages : en
Pages : 266

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Author: Martin Werner Grünewald
Publisher:
ISBN:
Category : Z bosons
Languages : en
Pages : 266

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Book Description

Author: Stefan Roth
Publisher: Springer
ISBN: 3540351655
Category : Science
Languages : en
Pages : 181

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Book Description
This book reviews recent contributions of electron positron colliders to the precision test of the electroweak Standard Model. It includes a short summary of the measurements at the Z resonance and gives an overview of the electroweak processes above the Z. Subsequently, measurements of the W mass at LEP are discussed in detail. Late chapters offer an outlook on electroweak physics at the future LHC. Also features many illustrations and tables.

Author: Michel Davier
Publisher: Atlantica Séguier Frontières
ISBN: 9782863320976
Category : Leptons (Nuclear physics)
Languages : en
Pages : 590

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Author: Justin Griffiths
Publisher:
ISBN:
Category : Large Hadron Collider (France and Switzerland)
Languages : en
Pages : 137

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The first measurement of the inclusive cross-section of the Z boson decaying to two tau leptons was measured with the ATLAS detector at the LHC. The data sample in this analysis represents an integrated luminosity of 35 pb ̄1 of proton-proton collisions at a center of mass energy of sqrt(s)=7 TeV. Separate measurements were performed in four decay modes based on how the two tau leptons decay: to hadrons and an electron, to hadrons and a muon, to an electron and a muon, and to two muons. In all four final states, inclusive cross-section measurements were made both in the fiducial region of the ATLAS detector where acceptance is high and in the full phase space, restricted to the mass range of [66, 116] GeV. The measurements from the four individual channels were then combined to yield the combined Z --> [tau] [tau] cross-section of 970 ± 70 (stat.) ± 60 (sys.) ± 30 (lumi.) pb.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 207

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This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 2003 summer conferences. Averages from Z resonance results are derived for hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the [tau] polarization asymmetries, the b{bar b} and c{bar c} partial widths and forward-backward asymmetries and the q{bar q} charge asymmetry. Above the Z resonance, averages are derived for di-fermion cross sections and forward-backward asymmetries, photon-pair, W-pair, Z-pair, single-W and single-Z cross sections, electroweak gauge boson couplings, W mass and width and W decay branching ratios. Also, an investigation of the interference of photon and Z-boson exchange is presented, and colour reconnection and Bose-Einstein correlation analyses in W-pair production are combined. The main changes with respect to the experimental results presented in summer 2002 are updates to the mass of the W boson, four-fermion cross sections and gauge couplings, all measured at LEP-2, and the LEP heavy-flavour results measured at the Z pole. The results are compared with precise electroweak measurements from other experiments, notably the recent final result on the electroweak mixing angle determined in neutrino-nucleon scattering by the NuTeV collaboration and the new result in atomic parity violation in Caesium. The parameters of the Standard Model are evaluated, first using the combined LEP electroweak measurements, and then using the full set of electroweak results.

Author: Silke Duensing
Publisher:
ISBN:
Category :
Languages : en
Pages : 129

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In this thesis the first measurement of {sigma}(p{bar p}) {yields} Z{sup 0} {yields} {tau}{bar {tau}} with the D0 detector at the Tevatron is presented. The tau pair candidates are recorded by the D0 detector using p{bar p} interactions at a center-of-mass energy of 1.96 TeV. Events in which one tau decays into a muon and the other tau final state is hadronic with one charged particle are selected for this analysis. The selection criteria for the hadronic tau decay are based on the tau final state, hence for two channels of one-prong taus: single charged pion ({tau}{sub {pi}}) and rho decays ({tau}{sub {rho}}). The selection is based on simple cuts on a number of discriminating variables and the cut values have been optimized for the best cross section measurement. Of hadronic tau candidates that have been reconstructed as {tau}{sub {pi}} candidates, 0.801 {+-} 0.017 {+-} 0.066 pass the selection cut; in the case of {tau}{sub {rho}} taus, the selection efficiency is 0.676 {+-} 0.009 {+-} 0.009. Of all QCD jets that are reconstructed as hadronic tau candidates, 0.0093 {+-} 0.0002 pass the {tau}{sub {pi}} selection cuts and 0.0122 {+-} 0.0002 the {tau}{sub {rho}} cuts. The cross section has been measured to be 274 {+-} 121 {+-} 40 {+-} 27 pb in the {mu}{tau}{sub {pi}} channel and 273 {+-} 40{sub -23}{sup +18} {+-} 27 pb in the {mu}{tau}{sub {rho}} channel, resulting in a combined measurement of {sigma}(p{bar p} {yields} Z{sup 0} {yields} {tau}{bar {tau}}) = 273 {+-} 38{sub -23}{sup +19} {+-} 27 pb which agrees with the SM prediction within errors. The errors are dominated by the statistical error as only the first data taken with the D0 detector in Run II was used. Due to the small set of tau candidates, the calorimeter energy scale could not yet be determined using data and this uncertainty is the largest systematic effect on the measurement. Another large contribution arises from the uncertainty of 10% on the luminosity measurement. This is expected to decrease significantly in the future. It was demonstrated that the currently available tools are sufficient to use tau leptons in the measurement of a SM process. This opens the door to the use of hadronic tau decays in the search for new particles, like SUSY particles, that decay preferentially to tau leptons in a number of models or the Higgs boson of either the SM or extended model. Doing physics at the Tevatron as the accelerator at the current energy frontier is our current best hope to find the yet elusive Higgs boson and will allow to either find proof of physics beyond the Standard Model or tighten the constraints on these models.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 266

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This dissertation describes a measurement of the forward-backward asymmetry(A{sub FB}) in p{bar p} → Z/[gamma]* → ee events using 5.0 fb−1 data collected by the D0 detector at the Fermilab Tevatron. The AFB is measured as a function of the invariant mass of the electron-positron pair. Along with obtaining normalized differential cross section 1/[sigma] x d[sigma]/dM and Z to light quark couplings, we measured the Standard Model(SM) fundamental parameter, the effective weak mixing angle sin2 [theta]{sub eff}{sup lept}, with an unprecedented precise in light quark sector, namely the single D0 measurement has surpassed the LEP combination of four experiment results of inclusive hadronic charge asymmetry.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 13

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The first measurement of the left-right cross section asymmetry (A{sub LR}) in Z° boson production has been made with the SLAC Large Detector (SLD) at the SLAC Linear Collider (SLC). The measurement was performed at a center-of-mass energy (E{sub cm}) of 91.55 GeV with a longitudinally polarized electron beam. The average beam polarization was (22.4 ± 0.6)%. Using a sample of 10,224 Z° decays, A{sub LR} is measured to be 0.102 ± 0.O44(stat) ± 0.003(syst), which determines the effective electroweak mixing angle to be sin2 [theta]{sub W}{sup eff} = 0.2375 ± 0.0056(stat) ± 0.0004(syst).