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Measurement of the forward-backward asymmetry in $Z \to b\overline{b}$ and $Z \to c\overline{c}$ decays with leptons

A. Heister S. Schael R. Barate 1 I. de Bonis 1 D. Decamp 1 C. Goy 1 J P. Lees 1 E. Merle 1 M N. Minard 1 B. Pietrzyk 1 G. Boix S. Bravo M. Chmeissani J M. Crespo E. Fernandez M. Fernandez-Bosman L. Garrido E. Grauges M. Martinez G. Merino R. Miquel L 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 L. Silvestris P. Tempesta A. Tricomi G. Zito X. Huang Jiali Lin Q. Ouyang T. Wang Y. Xie R. Xu S. Xue J. Zhang L. Zhang W. Zhao D. Abbaneo P. Azzurri O. Buchmuller 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 2 Alain Falvard 2 Pascal Gay 2 Pierre Henrard 2 J. Jousset 2 B. Michel 2 S. Monteil 2 Jean-Claude Montret 2 D. Pallin 2 Pascal Perret 2 J D. Hansen J R. Hansen P H. Hansen B S. Nilsson A. Waananen A. Kyriakis C. Markou E. Simopoulou A. Vayaki K. Zachariadou A. Blondel 3 G. Bonneaud 3 J C. Brient 3 A. Rouge 3 M. Rumpf 3 M. Swynghedauw 3 M. Verderi 3 H. Videau 3 V. Ciulli E. Focardi G. Parrini A. Antonelli M. Antonelli G. Bencivenni G. Bologna F. Bossi P. Campana G. Capon V. Chiarella P. Laurelli F. Murtas G P. Murtas L. Passalacqua M. Pepe-Altarelli A. Halley J G. Lynch P. Negus V. O'Shea C. Raine a S. Thompson S. Wasserbaech R. Cavanaugh S. Dhamotharan C. Geweniger P. Hanke G. Hansper V. Hepp E E. Kluge A. Putzer J. Sommer H. Stenzel K. Tittel S. Werner M. Wunsch R. Beuselinck D M. Binnie W. Cameron P J. Dornan M. Girone N. Marinelli J K. Sedgbeer J C. Thompson V M. Ghete P. Girtler E. Kneringer D. Kuhn G. Rudolph E. Bouhova-Thacker C K. Bowdery a J. Finch F. Foster G. Hughes R W L. Jones M R. Pearson N A. Robertson K. Jakobs K. Kleinknecht G. Quast B. Renk H G. Sander H. Wachsmuth C. Zeitnitz A. Bonissent 4 J. Carr 4 P. Coyle 4 O. Leroy 4 P. Payre 4 D. Rousseau 4 M. Talby 4 F. Ragusa A. David H. Dietl G. Ganis K. Huttmann G. Lutjens C. Mannert W. Manner H G. Moser R. Settles G. Wolf J. Boucrot 5 O. Callot 5 M. Davier 5 L. Duflot 5 J F. Grivaz 5 P. Heusse 5 A. Jacholkowska 5 J. Lefrancois 5 J J. Veillet 5 C. Yuan 5 G. Bagliesi T. Boccali L. Foa A. Giammanco A. Giassi F. Ligabue A. Messineo F. Palla G. Sanguinetti A. Sciaba R. Tenchini A. Venturi P G. Verdini G A. Blair G. Cowan M G. Green T. Medcalf A. Misiejuk J A. Strong P. Teixeira-Dias R W. Clifft T R. Edgecock P R. Norton I R. Tomalin B. Bloch-Devaux P. Colas S. Emery W. Kozanecki E. Lancon M C. Lemaire E. Locci P. Perez J. Rander J F. Renardy A. Roussarie J P. Schuller J. Schwindling A. Trabelsi B. Vallage N. Konstantinidis a M. Litke G. Taylor C N. Booth S. Cartwright F. Combley M H. Lehto L F. Thompson K. Affholderbach A. Bohrer S. Brandt C. Grupen A. Ngac G. Prange U. Sieler G. Giannini J E. Rothberg S R. Armstrong K. Berkelman K. Cranmer D P S. Ferguson Y. Gao S. Gonzalez O J. Hayes H. Hu S. Jin J. Kile P A. Mcnamara J. Nielsen y B. Pan J H. von Wimmersperg-Toller W. Wiedenmann J. Wu S L. Wu X. Wu G. Zobernig G. Dissertori
Abstract : 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 $Z \to b\bar{b}$ and $Z \to c\bar{c}$ events and the $B^0-\bar{B^0}$ average mixing parameter $\bar{\chi}$. Quark charges are tagged by the charges of electrons and muons produced in b and c semileptonic decays. Multivariate analyses are used to separate the event flavours and $b \to \ell$/$b \to c \to ell$ processes. The b and c quark asymmetries are measured simultaneously; the average mixing parameter and the pole asymmetries are determined to be \begin{eqnarray*} \bar{\chi} &=& 0.1196 \pm 0.0049 (stat) {}^{+0.0043}_{-0.0050} (syst) \\ \A^{0,b}_{FB} &=& 0.0998 \pm 0.0040 (stat) \pm 0.0017 (syst),\\ \A^{0.c}_{FB} &=& 0.0732 \pm 0.0053 (stat) \pm 0.0037 (syst).\\ \end{eqnarray*} 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 $\sin^2\theta^{eff}_{W} = 0.23188 \pm 0.00046$.
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A. Heister, S. Schael, R. Barate, I. de Bonis, D. Decamp, et al.. Measurement of the forward-backward asymmetry in $Z \to b\overline{b}$ and $Z \to c\overline{c}$ decays with leptons. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2002, 24, pp.177-191. ⟨in2p3-00011687⟩

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