Measurement of the forward-backward asymmetry in Z → bb̄ and Z → cc̄ decays with leptons: The ALEPH collaboration

A. Heister, S. Schael, R. Barate, I. De Bonis, D. Decamp, C. Goy, J. P. Lees, E. Merle, M. N. Minard, B. Pietrzyk, G. Boix, S. Bravo, M. P. Casado, M. Chmeissani, J. M. Crespo, E. Fernandez, M. Fernandez-Bosman, Ll Garrido, E. Graugés, M. MartinezG. Merino, R. Miquel, Ll M. Mir, A. Pacheco, H. Ruiz, A. Colaleo, D. Creanza, M. De Palma, G. Iaselli, G. Maggi, M. Maggi, S. Nuzzo, A. Ranieri, G. Raso, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, A. Tricomi, G. Zito, X. Huang, J. Lin, Q. Ouyang, T. Wang, Y. Xie, R. Xu, S. Xue, J. Zhang, L. Zhang, W. Zhao, D. Abbaneo, P. Azzurri, O. Buchmüller, M. Cattaneo, F. Cerutti, B. Clerbaux, H. Drevermann, R. W. Forty, M. Frank, F. Gianotti, T. C. Greening, J. B. Hansen, J. Harvey, D. E. Hutchcroft, P. Janot, B. Jost, M. Kado, P. Mato, A. Moutoussi, F. Ranjard, L. Rolandi, D. Schlatter, O. Schneider, G. Sguazzoni, W. Tejessy, F. Teubert, A. Valassi, I. Videau, J. Ward, F. Badaud, A. Falvard, P. Gay, P. Henrard, J. Jousset, B. Michel, S. Monteil, J. C. Montret, D. Pallin, P. Perret, J. D. Hansen, J. R. Hansen, P. H. Hansen, B. S. Nilsson, A. Wäänänen, A. Kyriakis, C. Markou, E. Simopoulou, A. Vayaki, K. Zachariadou, A. Blondel

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The sample of hadronic Z decays collected by the ALEPH detector at LEP in the years 1991-1995 is analysed in order to measure the forward-backward asymmetry in Z → bb̄ and Z → cc̄ events and the B 0 -B̄ 0 average mixing parameter χ̄. Quark charges are tagged by the charges of electrons and muons produced in b and e semileptonic decays. Multivariate analyses are used to separate the event flavours and b → ℓ/b → c → ℓ processes. The b and c quark asymmetries are measured simultaneously; the average mixing parameter and the pole asymmetries are determined to be χ̄ = 0.1196 ± 0.0049 (stat.) -0.0050+0.0043 (syst.), A FB0,b = 0.0998 ± 0.0040 (stat.) ± 0.0017 (syst.), A FB0,c = 0.0732 ± 0.0053 (stat.) ± 0.0037 (syst.). These asymmetries, combined with the ALEPH measurements of the b asymmetry using inclusive b hadron decays and of the c asymmetry using reconstructed D mesons, correspond to a value of the effective electroweak mixing angle of sin 2 θ Weff = 0.23188 ± 0.00046.
Original languageEnglish
Pages (from-to)177-191
JournalEuropean Physical Journal C
Issue number2
Publication statusPublished - 1 Jan 2002

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    Heister, A., Schael, S., Barate, R., De Bonis, I., Decamp, D., Goy, C., Lees, J. P., Merle, E., Minard, M. N., Pietrzyk, B., Boix, G., Bravo, S., Casado, M. P., Chmeissani, M., Crespo, J. M., Fernandez, E., Fernandez-Bosman, M., Garrido, L., Graugés, E., ... Blondel, A. (2002). Measurement of the forward-backward asymmetry in Z → bb̄ and Z → cc̄ decays with leptons: The ALEPH collaboration. European Physical Journal C, 24(2), 177-191.