Update of electroweak parameters from $Z$ decays

The ALEPH collaboration Buskulic, D. ; Decamp, D. ; Goy, C. ; et al.
Z.Phys.C 60 (1993) 71-82, 1993.
Inspire Record 354298 DOI 10.17182/hepdata.47312

Based on 520 000 fermion pairs accumulated during the first three years of data collection by the ALEPH detector at LEP, updated values of the resonance parameters of theZ are determined to beMZ=(91.187±0.009) GeV, ΓZ=(2.501±0.012) GeV, σhad0=(41.60±0.27) nb, andRℓ=20.78±0.13. The corresponding number of light neutrino species isNν=2.97±0.05. The forward-backward asymmetry in lepton-pair decays is used to determine the ratio of vector to axial-vector couplings of leptons:gV2(MZ2)/gA2(MZ2)=0.0052±0.0016. Combining this with ALEPH measurements of theb andc quark asymmetries and τ polarization gives sin2θWeff=0.2326±0.0013. Assuming the minimal Standard Model, and including measurements ofMW/MZ fromp\(\bar p\) colliders and neutrino-nucleon scattering, the mass of the top quark is\(M_{top} = 156 \pm \begin{array}{*{20}c} {22} \\ {25} \\ \end{array} \pm \begin{array}{*{20}c} {17} \\ {22Higgs} \\ \end{array} \) GeV.

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Data for 1991 running period.

Data for 1991 running period.

Data for 1991 running period.


Improved measurements of electroweak parameters from $Z$ decays into fermion pairs

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Goy, C. ; et al.
Z.Phys.C 53 (1992) 1-20, 1992.
Inspire Record 317141 DOI 10.17182/hepdata.14857

The properties of theZ resonance are measured on the basis of 190 000Z decays into fermion pairs collected with the ALEPH detector at LEP. Assuming lepton universality,Mz=(91.182±0.009exp±0.020L∶P) GeV,ГZ=(2484±17) MeV, σhad0=(41.44±0.36) nb, andГjad/Гℓℓ=21.00±0.20. The corresponding number of light neutrino species is 2.97±0.07. The forward-back-ward asymmetry in leptonic decays is used to determine the ratio of vector to axial-vector coupling constants of leptons:gv2(MZ2)/gA2(MZ2)=0.0072±0.0027. Combining these results with ALEPH results on quark charge and\(b\bar b\) asymmetries, and τ polarization, sin2θW(MZ2). In the contex of the Minimal Standard Model, limits are placed on the top-quark mass.

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Measurement of electroweak parameters from Z decays into Fermion pairs

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Goy, C. ; et al.
Z.Phys.C 48 (1990) 365-392, 1990.
Inspire Record 298414 DOI 10.17182/hepdata.47314

We report on the properties of theZ resonance from 62 500Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We findMZ=(91.193±0.016exp±0.030LEP) GeV, ΓZ=(2497±31) MeV, σhad0=(41.86±0.66)nb, and for the partial widths Γinv=(489±24) MeV, Γhad(1754±27) MeV, Γee=(85.0±1.6)MeV, Γμμ=(80.0±2.5) MeV, and Γττ=(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 Γu=(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,gv2(MZ2)=(0.12±0.12)×10−2 andgA2(MZ2)=0.2528±0.0040. The number of light neutrino species isNν=2.91±0.13; the electroweak mixing angle is sin2θW(MZ2)=0.2291±0.0040.

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Study of fermion pair production in $e^{+} e^{-}$ collisions at 130-GeV to 183-GeV

The ALEPH collaboration Barate, R. ; Decamp, D. ; Ghez, Philippe ; et al.
Eur.Phys.J.C 12 (2000) 183-207, 2000.
Inspire Record 498072 DOI 10.17182/hepdata.49128

The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented. Results for ee, mumu, tautau, qq, bb and cc production show no significant deviation from the Standard Model predictions. This enable constraints to be set upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, Z' bosons and R-parity violating squarks and sneutrinos. Limits on the energy scale Lambda of eeff contact interactions are typically in the range from 2-10 TeV. Limits on R-parity violating sneutrinos reach masses of a few hundred GeV for large values of their Yukawa couplings.

1 data table match query

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Study of the muon pair production at center-of-mass energies from 20-GeV to 136-GeV with the ALEPH detector

The ALEPH collaboration Barate, R. ; Buskulic, D. ; Decamp, D. ; et al.
Phys.Lett.B 399 (1997) 329-341, 1997.
Inspire Record 440218 DOI 10.17182/hepdata.47490

The total cross section and the forward-backward asymmetry for the process e + e − → μ + μ − ( nγ ) are measured in the energy range 20–136 GeV by reconstructing the effective centre-of-mass energy after initial state radiation. The analysis is based on the data recorded with the ALEPH detector at LEP between 1990 and 1995, corresponding to a total integrated luminosity of 143.5 pb −1 . Two different approaches are used: in the first one an exclusive selection of events with hard initial state radiation in the energy range 20–88 GeV is directly compared with the Standard Model predictions showing good agreement. In the second one, all events are used to obtain a precise measurement of the energy dependence of σ 0 and A FB 0 from a model independent fit, enabling constraints to be placed on models with extra Z bosons.

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Exlclusive analysis from events with hard ISR.

Inclusive analysis from evvents with no specific selection of hard ISR.


Measurement of hadron and lepton pair production from $e^{+} e^{-}$ annihilation at center-of-mass energies of 130-GeV and 136-GeV

The ALEPH collaboration Buskulic, D. ; De Bonis, I. ; Decamp, D. ; et al.
Phys.Lett.B 378 (1996) 373-384, 1996.
Inspire Record 421552 DOI 10.17182/hepdata.47801

Hadronic and leptonic cross-sections and forward-backward asymmetries are measured using 5.7 pb −1 of data taken with the ALEPH detector at LEP at centre-of-mass energies of 130 and 136 GeV. The results agree with Standard Model expectations. The measurement of hadronic cross-sections far away from the Z resonance improves the determination of the interference between photon and Z exchange. Constraints on models with extra Z bosons are presented.

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Forward-Backward Asymmetry with loose SPRIME cuts.

Forward-Backward Asymmetry with tight SPRIME cuts.

Forward-Backward Asymmetry with loose SPRIME cuts.

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Measurements of cross-section and charge asymmetry for e+ e- ---> mu+ mu- and e+ e- ---> tau+ tau- at s**(1/2) = 57.8-GeV

The AMY collaboration Velissaris, C. ; Lusin, S. ; Chung, Y.S. ; et al.
Phys.Lett.B 331 (1994) 227-235, 1994.
Inspire Record 373861 DOI 10.17182/hepdata.38344

With data corresponding to 142 pb −1 accumulated at s = 57.8 GeV by the AMY detector at TRISTAN we measure the cross section of the reactions e + e − → μ + μ − and e + e − → τ + τ − and the symmetry in the angular distributions. For the lowest order cross section we obtain σ μμ = 27.54 ± 0.65 ± 0.95 pb and σ ττ = 28.27 ± 0.87 ± 0.69 pb, and for the forward-backward asymmetry, A μμ = 0.303 ± 0.027 ± 0.008 and A ττ = −0.291 ± 0.040 ± 0.019. These measurements agree with the standard model. Assuming e − μ − τ univrsality we extract the vector and axial coupling constants | gν | = 0.00 ± 0.09 and | g A | = 0.476 ± 0.024. A fit of data to composite models places lower bounds (95% confidence level) on the compositeness scale of 2–4 TeV.

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Lowest order cross section and forward-backward asymmetry.

Lowest order cross section and forward-backward asymmetry.


Measurement of the forward - backward asymmetry in $e^{+} e^{-} \to b \bar{b}$ and the $b$ quark branching ratio to muons at TRISTAN using neural networks

The AMY collaboration Ueno, K. ; Kanda, S. ; Olsen, S.L. ; et al.
Phys.Lett.B 381 (1996) 365-371, 1996.
Inspire Record 418709 DOI 10.17182/hepdata.38513

The forward-backward asymmetry in e + e − → b b at s = 57.9 GeV and the b-quark branching ratio to muons have been measured using neural networks. Unlike previous methods for measuring the b b forward-backward asymmetry where the estimated background from c -quark decays and other sources are subtracted, here events are categorized as either b b or non- b b events by neural networks based on event-by-event characteristics. The determined asymmetry is −0.429 ± 0.044 (stat) ± 0.047 (sys) and is consistent with the prediction of the standard model. The measured B B mixing parameter is 0.136 ± 0.037 (stat) ± 0.040 (sys) ± 0.002 (model) and the measured b-quark branching ratio to muons is 0.122 ± 0.006 (stat) ± 0.007 (sys).

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A measurement of $e^+e^- \to b\bar{b}$ forward - backward charge asymmetry between $\sqrt{s} = 52$ GeV and 57-GeV

The AMY collaboration Sagawa, H. ; Lim, J. ; Abe, K. ; et al.
Phys.Rev.Lett. 63 (1989) 2341, 1989.
Inspire Record 279824 DOI 10.17182/hepdata.19996

Using 123 multihadronic inclusive muon-production e+e− annihilation events at an average c.m. energy of 55.2 GeV, we extracted the forward-backward charge asymmetry of the e+e−→bb¯ process and the R ratio for bb¯ production. We used an analysis method in which the behavior of the c quark and lighter quarks is assumed, with only that of the b quark left indeterminate. The results, Ab=-0.72±0.28(stat)±0.13(syst) and Rb=0.57±0.16±0.10, are consistent with the standard model.

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Asymmetry in BOTTOM quark production.


Measurements of cross-section and asymmetry for e+ e- ---> b anti-b and heavy quark fragmentation at KEK TRISTAN

The AMY collaboration Liu, F. ; Chinitz, L.M. ; Abe, K. ; et al.
Phys.Rev.D 49 (1994) 4339-4347, 1994.
Inspire Record 381324 DOI 10.17182/hepdata.22547

Using 773 muons found in hadronic events from 142 pb−1 of data at a c.m. energy of 57.8 GeV, we extract the cross section and forward-backward charge asymmetry for the e+e−→bb¯ process, and the heavy quark fragmentation function parameters for the Peterson model. For the analysis of the e+e−→bb¯ process, we use a method in which the behavior of the c quark and lighter quarks is assumed, with only that of the b quark left indeterminate. The cross section and asymmetry for e+e−→bb¯ are found to be Rb = 0.57 ± 0.06(stat) ± 0.08(syst) and Ab = −0.59 ± 0.09 ± 0.09, respectively. They are consistent with the standard model predictions. For the study of the fragmentation function we use the variable 〈xE〉, the fraction of the beam energy carried by the heavy hadrons. We obtain 〈xE〉c=0.56−0.05−0.03+0.04+0.03 and 〈xE〉b=0.65−0.04−0.06+0.06+0.05, respectively. These are in good agreement with previously measured values.

1 data table match query

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