Abstract
Precise values of theZ resonance cross sections and lepton pair forward-backward asymmetries are measured from a sample of 1.3 millionZ 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 σ 0 h =(41.60±0.16) nb, andR l =20.69±0.09. The corresponding number of light neutrino species isN 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 2 V (M 2 Z )/g 2 A (M 2 Z )=0.0058 ±0.0011. An application of these results to constrain one model with extraZ bosons is presented.
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Supported by CICYT, Spain
Supported by the National Science Foundation of China
Supported by the Danish Natural Science Research Council
Supported by the UK Science and Engineering Research Council
Supported by the US Department of Energy, contract DE-AC02-76ER00881
Supported by the US Department of Energy, contract DE-FG05-92ER40742
Supported by the US Department of Energy, contract DE-FC05-85ER250000
Supported by the Bundesministerium für Forschung und Technologie, Fed. Rep. of Germany
Supported by the Direction des Sciences de la Matière, C.E.A.
Supported by Fonds zur Förderung der wissenschaftlichen Forschung, Austria
Supported by the US Department of Energy, grant DE-FG03-92ER40689
Partially supported by Colciencias Colombia
Also at Istituto di Matematica e Fisica, Università di Sassari, Sassari, Italy
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ALEPH Collaboration., Buskulic, D., Casper, D. et al. Z production cross sections and lepton pair forward-backward asymmetries. Z. Phys. C - Particles and Fields 62, 539–550 (1994). https://doi.org/10.1007/BF01574159
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DOI: https://doi.org/10.1007/BF01574159