The production of electrons with very high transverse momentum has been studied in the UA2 experiment at the CERN\(\bar pp\) collider (\(\sqrt s\)=540 GeV). From a sample of events containing an electron candidate withpT>15 GeV/c, we extract a clear signal resulting from the production of the charged intermediate vector bosonW±, which subsequently decays into an electron and a neutrino. We study theW production and decay properties. Further-more, we refine our results on the production and decay of the neutral vector bosonZ0. Finally, we compare the experimental results to the predictions of the standard model of the unified electro-weak theory.
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An analysis of W- and Z-boson production using data from the Collider Detector at Fermilab at √s =1.8 TeV yields σ(W→ev)/σ(Z→ee)=10.2±0.8(stat)±0.4(syst). The width of the W boson, Γ(W), and a limit on the top-quark mass independent of decay mode are extracted from this measurement.
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The properties of a sample of 172 charged intermediate vector bosons decaying in the (eνe) channel and 16 neutral intermediate vector bosons decaying in the (e+e-) channel are described. Masses, decay widths, decay angular distributions, and production cross-sections are given; they are shown to be in excellent agreement with the expectations of the SU2 ⊗ U1 standard model. A limit is put on the number of light-neutrino types Nν ≤ 10 at 90% c.l.
W CROSS SECTIONS ARE GIVEN IN ARNISON ET AL., NC 44A, 1.
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A study ofW± andZ0 properties has been performed using the UA2 detector at the\(\bar pp\) collider. The data correspond to a total integrated luminosity of 142 nb−1 at\(\sqrt s \)=546 GeV, and of 310 nb−1 at\(\sqrt s \)=630 GeV. The experimental results are compared with the predictions of the Standard Model of the unified electroweak theory.
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We present updated results from the UA1 experiment on cross sections times leptonic branching ratios for intermediate vector bosons produced in proton-antiproton collisions at a centre-of-mass energy of 0.630 TeV. We find that σ·B( W → l βn)=0.63±0.04±0.10 nb and σ·B( Z 0 → l + l − =0.071±0.011 nb where l denotes an average of electron and muon channels. An average over all data (electron and muon channels at 0.546 and 0.630 TeV) gives a ratio of R≡σ·( W → l ν)/σ·B( Z 0 → l + l − ) = 9.1 +1.7 −1.2 . Using current theoretical predictions for this quantity, limits are extracted on the number of light neutrino types. Combining UA1 and UA2 data and imposing the bound N ν ⩾3 we find that N ν ⩽5.9 at 90% CL. Constraints on the mass of the top quark are also discussed.
THE CORRESPONDING VALUE FROM UA2 IS BR*SIG = 0.61+-0.10+-0.07.
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THE CORRESPONDING VALUE FROM UA2 IS BR*SIG = 0.57+-0.04+-0.07.
An extensive study of production and decay properties of charged and neutral Intermediate Vector Bosons (IVB) at the CERN proton-antiproton collider is presented. Intermediate Vector Bosons were detected in the electron, muon, and tau decay modes at centre-of-mass energies of 0.546 and 0.630 TeV. This paper is a summary, based on all the available data from the UA1 experiment from the running periods 1982–1985. Results are presented and compared with expectations of the Standard Eletroweak Model and QCD-improved Drell-Yan annihilation processes. The general conclusion is that there is an excellent agreement between the predictions of the Standard Model and our measurements.
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Results on the production cross sections ofW andZ bosons detected in the UA2 experiment are given based on a large sample ofW→eν andZ→e+e− decays. The measured cross sections are σWe = 660±15(stat)±37(syst)pb, σZe = 70.4±5.5(stat)±4.0(syst)pb and their ratioR=9.38−0.72+0.82(stat)±0.25(syst). In the framework of the Standard Model, the measured value ofR is used to determine the total width of theW, Γ(W)=2.30±0.19(stat)±0.06(syst) GeV.
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A study of the two-jet mass spectrum measured with the UA 2 calorimeter has revealed a signal from hadronic decays ofW andZ bosons above a large background. Production and decay properties of the signal have been measured. The combined production cross-section σ·B(W, Z → two jets) is 9.6±2.3 (stat.)±1.1 (syst.) nb, compared with an expectation of 5.8 nb calculated to order αs2. A limit on the production cross-section of additional heavy vector bosons decaying into two jets is given as a function of the boson mass.
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An analysis of high-transverse-momentum electrons using data from the Collider Detector at Fermilab (CDF) of p¯p collisions at s=1800 GeV yields values of the production cross section times branching ratio for W and Z0 bosons of σ(p¯p→WX→eνX)=2.19±0.04(stat)±0.21(syst) nb and σ(p¯p→Z0X→e+e−X)=0.209±0.013(stat)±0.017(syst) nb. Detailed descriptions of the CDF electron identification, background, efficiency, and acceptance are included. Theoretical predictions of the cross sections that include a mass for the top quark larger than the W mass, current values of the W and Z0 masses, and higher-order QCD corrections are in good agreement with these measured values.
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An analysis of W and Z boson production at UA1, using 4.66 pb −1 of data from the 1988 and 1989 CERN p p Collider runs at s =0.63 TeV , yields R ≡ σ W Br(W→ μ v)/ σ z Br( Z → μμ )=10.4 −1.5 +1.8 stat.±0.8(syst.) We find R =9.5 −1.0 +1.1 (stat.+syst.) when combining all available UA1 data, in both the electron and muon channel, taken in the period 1983–1989. In the framework of the standard model, the value of R is used to infer the total width of the W boson, Γ W tot =2.18 −0.24 +0.26 (exp.)±0.04(theory) GeV/ c 2 .
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