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 --> b (b) over bar and Z --> cc events and the B(0)-(B) over bar (0) average mixing parameter (chi) over bar. 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 --> 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 (chi) over bar = 0.1196 +/- 0.0049 (stat.) (+0.0043)(-0.0050) (syst.), A(FB)(0,b) = 0.0998 +/- 0.0040 (stat.) +/- 0.0017 (syst.), A(FB)(0,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)theta(W)(eff) = 0.23188 +/- 0.00046. RI ANTONELLI, ANTONELLA/C-6238-2011; Jones, Roger/H-5578-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; O'Shea, Val/G-1279-2010

Measurement of the forward-backward asymmetry in Z -> b(b)over-bar and Z -> c(c)over-bar decays with leptons

TRICOMI, Alessia Rita;
2002

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 --> b (b) over bar and Z --> cc events and the B(0)-(B) over bar (0) average mixing parameter (chi) over bar. 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 --> 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 (chi) over bar = 0.1196 +/- 0.0049 (stat.) (+0.0043)(-0.0050) (syst.), A(FB)(0,b) = 0.0998 +/- 0.0040 (stat.) +/- 0.0017 (syst.), A(FB)(0,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)theta(W)(eff) = 0.23188 +/- 0.00046. RI ANTONELLI, ANTONELLA/C-6238-2011; Jones, Roger/H-5578-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; O'Shea, Val/G-1279-2010
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11769/13543
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