From measurements of the cross sections for e+e-→ hadrons and the cross sections and forward-backward charge-asymmetries for ee-→e+e-, μ+μ-and π+π-at several centre-of-mass energies around the Z0pole with the DELPHI apparatus, using approximately 150 000 hadronic and leptonic events from 1989 and 1990, one determines the following Z0parameters: the mass and total width MZ= 91.177 ± 0.022 GeV, ΓZ = 2.465 ± 0.020 GeV, the hadronic and leptonic partial widths Γh= 1.726 ± 0.019 GeV, Γl= 83.4 ± 0.8 MeV, the invisible width Γinv= 488 ± 17 MeV, the ratio of hadronic over leptonic partial widths RZ= 20.70 ± 0.29 and the Born level hadronic peak cross section σ0= 41.84±0.45 nb. A flavour-independent measurement of the leptonic cross section gives very consistent results to those presented above (Γl= 83.7 ± 0.8rmMeV). From these results the number of light neutrino species is determined to be Nv= 2.94 ±0.10. The individual leptonic widths obtained are: Γe= 82.4±_1.2 MeV, Γu= 86.9±2.1 MeV and Γτ= 82.7 ± 2.4 MeV. Assuming universality, the squared vector and axial-vector couplings of the Z0to charged leptons are: V ̄l2= 0.0003±0.0010 and A ̄l2= 0.2508±0.0027. These values correspond to the electroweak parameters: ρvarianteff= 1.003 ± 0.011 and sin2θWeff= 0.241 ± 0.009. Within the Minimal Standard Model (MSM), the results can be expressed in terms of a single parameter: sin2θWM ̄S= 0.2338 ± 0.0027. All these values are in good agreement with the predictions of the MSM. Fits yield 43<mtop< 215 GeV at the 95% level. Finally, the measured values of ΓZand Γinvare used to derived lower mass bounds for possible new particles. © 1991.

Abreu, P., Adam, W., Adami, F., Adye, T., Akesson, T., Alekseev, G., et al. (1991). Determination of Z0 resonance parameters and couplings from its hadronic and leptonic decays. NUCLEAR PHYSICS. B, 367(3), 511-574 [10.1016/0550-3213(91)90007-K].

Determination of Z0 resonance parameters and couplings from its hadronic and leptonic decays

Calvi, M.;Pullia, A.;Ragazzi, S.;Tabarelli, T.;
1991

Abstract

From measurements of the cross sections for e+e-→ hadrons and the cross sections and forward-backward charge-asymmetries for ee-→e+e-, μ+μ-and π+π-at several centre-of-mass energies around the Z0pole with the DELPHI apparatus, using approximately 150 000 hadronic and leptonic events from 1989 and 1990, one determines the following Z0parameters: the mass and total width MZ= 91.177 ± 0.022 GeV, ΓZ = 2.465 ± 0.020 GeV, the hadronic and leptonic partial widths Γh= 1.726 ± 0.019 GeV, Γl= 83.4 ± 0.8 MeV, the invisible width Γinv= 488 ± 17 MeV, the ratio of hadronic over leptonic partial widths RZ= 20.70 ± 0.29 and the Born level hadronic peak cross section σ0= 41.84±0.45 nb. A flavour-independent measurement of the leptonic cross section gives very consistent results to those presented above (Γl= 83.7 ± 0.8rmMeV). From these results the number of light neutrino species is determined to be Nv= 2.94 ±0.10. The individual leptonic widths obtained are: Γe= 82.4±_1.2 MeV, Γu= 86.9±2.1 MeV and Γτ= 82.7 ± 2.4 MeV. Assuming universality, the squared vector and axial-vector couplings of the Z0to charged leptons are: V ̄l2= 0.0003±0.0010 and A ̄l2= 0.2508±0.0027. These values correspond to the electroweak parameters: ρvarianteff= 1.003 ± 0.011 and sin2θWeff= 0.241 ± 0.009. Within the Minimal Standard Model (MSM), the results can be expressed in terms of a single parameter: sin2θWM ̄S= 0.2338 ± 0.0027. All these values are in good agreement with the predictions of the MSM. Fits yield 43
Articolo in rivista - Articolo scientifico
Nuclear and High Energy Physics
English
1991
367
3
511
574
none
Abreu, P., Adam, W., Adami, F., Adye, T., Akesson, T., Alekseev, G., et al. (1991). Determination of Z0 resonance parameters and couplings from its hadronic and leptonic decays. NUCLEAR PHYSICS. B, 367(3), 511-574 [10.1016/0550-3213(91)90007-K].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/187140
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