The properties of the Z resonance are measured on the basis of 190000 Z decays into fermion pairs collected with the ALEPH detector at LEP. Assuming lepton universality, M(Z) = (91.182 +/- 0.009(exp.) +/- 0.020 (Z->b bbar)) GeV, GAMMA(Z) = (2484 +/- 17) MeV, sigma(had)0 = (41.44 +/- 0.36) nb, and GAMMA(had)/GAMMA(ll) = 21.00 +/- 0.20. The corresponding number of light neutrino species is 2.97 +/- 0.07. The forward-backward asymmetry in leptonic decays is used to determine the ratio of vector to axial-vector coupling constants of leptons: g(V)2(M(Z)2)/g(A)2(M(Z)2) = 0.0072 +/- 0.0027. Combining these results with ALEPH results on quark charge and b bbar asymmetries, and tau-polarization, sin^2( theta(W)(M^2(Z))) = 0.2312 +/- 0.0018. In the context of the Minimal Standard Model, limits are placed on the top-quark mass.
Improved Measurements of Electroweak Parameters From Z-decays Into Fermion Pairs
BATIGNANI, GIOVANNI;CIOCCI, MARIA AGNESE;FERRANTE, ISIDORO;FIDECARO, FRANCESCO;F. FORTI;GIORGI, MARCELLO;MESSINEO, ALBERTO MARIA;TONELLI, GUIDO EMILIO;G. TRIGGIANI;
1992-01-01
Abstract
The properties of the Z resonance are measured on the basis of 190000 Z decays into fermion pairs collected with the ALEPH detector at LEP. Assuming lepton universality, M(Z) = (91.182 +/- 0.009(exp.) +/- 0.020 (Z->b bbar)) GeV, GAMMA(Z) = (2484 +/- 17) MeV, sigma(had)0 = (41.44 +/- 0.36) nb, and GAMMA(had)/GAMMA(ll) = 21.00 +/- 0.20. The corresponding number of light neutrino species is 2.97 +/- 0.07. The forward-backward asymmetry in leptonic decays is used to determine the ratio of vector to axial-vector coupling constants of leptons: g(V)2(M(Z)2)/g(A)2(M(Z)2) = 0.0072 +/- 0.0027. Combining these results with ALEPH results on quark charge and b bbar asymmetries, and tau-polarization, sin^2( theta(W)(M^2(Z))) = 0.2312 +/- 0.0018. In the context of the Minimal Standard Model, limits are placed on the top-quark mass.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.