Measurement of the e+e-→W+W- cross section and W decay branching fractions at LEP

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2007-12, Vol.52 (4), p.767-785
• Main Authors: Abbiendi, G., Ainsley, C., Åkesson, P.F., Alexander, G., Anagnostou, G., Anderson, K.J., Asai, S., Axen, D., Bailey, I., Barberio, E., Barillari, T., Barlow, R.J., Batley, R.J., Bechtle, P., Behnke, T., Bell, K.W., Bell, P.J., Bella, G., Bellerive, A., Benelli, G., Bethke, S., Biebel, O., Boeriu, O., Bock, P., Boutemeur, M., Braibant, S., Brown, R.M., Burckhart, H.J., Campana, S., Capiluppi, P., Carnegie, R.K., Carter, A.A., Carter, J.R., Chang, C.Y., Charlton, D.G., Ciocca, C., Csilling, A., Cuffiani, M., Dado, S., Dallavalle, M., De Roeck, A., De Wolf, E.A., Desch, K., Dienes, B., Dubbert, J., Duchovni, E., Duckeck, G., Duerdoth, I.P., Etzion, E., Fabbri, F., Ferrari, P., Fiedler, F., Fleck, I., Ford, M., Frey, A., Gagnon, P., Gary, J.W., Geich-Gimbel, C., Giacomelli, G., Giacomelli, P., Giunta, M., Goldberg, J., Gross, E., Grunhaus, J., Gruwé, M., Gupta, A., Hajdu, C., Hamann, M., Hanson, G.G., Harel, A., Hauschild, M., Hawkes, C.M., Hawkings, R., Herten, G., Heuer, R.D., Hill, J.C., Horváth, D., Igo-Kemenes, P., Ishii, K., Jeremie, H., Jovanovic, P., Junk, T.R., Kanzaki, J., Karlen, D., Kawagoe, K., Kawamoto, T., Keeler, R.K., Kellogg, R.G., Kennedy, B.W., Kluth, S., Kobayashi, T., Kobel, M., Komamiya, S., Krämer, T., Krasznahorkay, A., Krieger, P., von Krogh, J., Kuhl, T., Kupper, M., Lafferty, G.D.
• Format: Article
• Language: English
• Subjects: Cross-sections; Hadrons; Leptons; Pair production
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-007-0442-0

From a total data sample of 701.1 pb-1 recorded with e+e- centre-of-mass energies of \(\sqrt{s} =\)161–209 GeV with the OPAL detector at LEP, 11693 W-pair candidate events are selected. These data are used to obtain measurements of the W-pair production cross sections at 10 different centre-of-mass energies. The ratio of the measured cross sections to the standard model expectation is found to be: \({\text{data}}/{{\text{SM}}} = 1.002\pm0.011 ({\text{stat.}}) \pm0.007 ({\text{syst.}}) \pm0.005 ({\text{theory}})\), where the uncertainties are statistical, experimental systematics and theory systematics respectively. The data are used to determine the W boson branching fractions, which are found to be consistent with lepton universality of the charged current interaction. Assuming lepton universality, the branching ratio to hadrons is determined to be 67.41±0.37(stat.)±0.23(syst.)%, from which the CKM matrix element |Vcs| is determined to be 0.969±0.017(stat.)±0.012(syst.). The differential cross section as a function of the W- production angle is measured for the qqeν and qqμν final states. The results described in this paper are consistent with the expectations from the standard model.