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Z-PRODUCTION CROSS-SECTIONS AND LEPTON PAIR FORWARD-BACKWARD ASYMMETRIES

BUSKULIC, D; CASPER, D; DEBONIS, I; DECAMP, D; GHEZ, P; GOY, C; ... ZOBERNIG, G; + view all (1994) Z-PRODUCTION CROSS-SECTIONS AND LEPTON PAIR FORWARD-BACKWARD ASYMMETRIES. Z PHYS C PART FIELDS , 62 (4) 539 - 550.

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Abstract

Precise values of the Z resonance cross sections and lepton pair forward-backward asymmetries are measured from a sample of 1.3 million Z decays into hadrons and charged leptons taken with the ALEPH detector at LEP. A silicon-tungsten luminosity calorimeter was installed in ALEPH in 1992, permitting the determination of the absolute luminosity to a systematic precision of 0.15% (experimental) and 0.25% (theoretical). This is combined with a better understanding of the hadronic event selection and an improved tau pair selection. Including the ALEPH results of the past three years one obtains sigma(h)0 = (41.60 +/- 0.16) nb, and R(l) = 20.69 +/- 0.09. The corresponding number of light neutrino species is N(v) = 2.983 +/- 0.034. The lepton pair forward-backward' asymmetry is used to derive the ratio of vector to axial-vector couplings of leptons: g(V)2(M(Z)2)/g(A)2(M(Z)2) = 0.0058 +/- 0.0011. An application of these results to constrain one model with extra Z bosons is presented.

Type:Article
Title:Z-PRODUCTION CROSS-SECTIONS AND LEPTON PAIR FORWARD-BACKWARD ASYMMETRIES
Keywords:SEMILEPTONIC NEUTRINO SCATTERING, ELECTROWEAK MIXING ANGLE, GRAND UNIFIED THEORIES, HADRONIC Z-DECAYS, BHABHA SCATTERING, PRECISE DETERMINATION, RADIATIVE-CORRECTIONS, PHOTON CORRECTIONS, MASS CORRECTIONS, ALEPH DETECTOR
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy

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