We report on the properties of the Z resonance from 62500 Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We find M_Z =(91.193+/-0.016 (exp)+/-0.030 (LEP) ) GeV, Gamma-Z= (2497+/-31) MeV, sigma_had= (41+/-0.66) nb, and for the partial widths Gamma_vis= (489 +/- 24) MeV, Gamma_had= (1754 +/- 27) MeV, Gamma_ee=(85.0+/-1.6) MeV =(85.0±1.6)MeV, Gamma_mumu=(80+/-2.5) MeV and Gamma_tautau=(81.3+/-2.5) MeV, all in good agreement with the Standard Model. Assuming lepton universality and using a lepton sample without distinction of the final state we measure Gamma_ll=(84.3+/-1.3) MeV. The forward-backward asymmetry in leptonic decays is used to determine the vector and axial-vector weak coupling constants of leptors, g_v^ 2 ( (M_ Z) ^2 )=(0.12+/-0.12)x10^-2) and g_A^ 2 ( (M_ Z) ^2 )=0.2528 +/- 0.0040. The number of light neutrino species is N_nu =2.91+/- 0.13; the electroweak mixing angle is (sin(teta_ W ((M_ Z)^ 2 )))^2=0.2291+/-0.0040.
Measurement of electroweak parameters from Z decays into fermion pairs
BATIGNANI, GIOVANNI;CIOCCI, MARIA AGNESE;FERRANTE, ISIDORO;FIDECARO, FRANCESCO;FORTI, FRANCESCO;GIORGI, MARCELLO;MESSINEO, ALBERTO MARIA;TONELLI, GUIDO EMILIO;TRIGGIANI, GIUSEPPE;
1990-01-01
Abstract
We report on the properties of the Z resonance from 62500 Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We find M_Z =(91.193+/-0.016 (exp)+/-0.030 (LEP) ) GeV, Gamma-Z= (2497+/-31) MeV, sigma_had= (41+/-0.66) nb, and for the partial widths Gamma_vis= (489 +/- 24) MeV, Gamma_had= (1754 +/- 27) MeV, Gamma_ee=(85.0+/-1.6) MeV =(85.0±1.6)MeV, Gamma_mumu=(80+/-2.5) MeV and Gamma_tautau=(81.3+/-2.5) MeV, all in good agreement with the Standard Model. Assuming lepton universality and using a lepton sample without distinction of the final state we measure Gamma_ll=(84.3+/-1.3) MeV. The forward-backward asymmetry in leptonic decays is used to determine the vector and axial-vector weak coupling constants of leptors, g_v^ 2 ( (M_ Z) ^2 )=(0.12+/-0.12)x10^-2) and g_A^ 2 ( (M_ Z) ^2 )=0.2528 +/- 0.0040. The number of light neutrino species is N_nu =2.91+/- 0.13; the electroweak mixing angle is (sin(teta_ W ((M_ Z)^ 2 )))^2=0.2291+/-0.0040.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.