HEPData Search

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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.

15 data tables match query

Table 1

Data from 1990 running period.

Table 2

Data from 1990 running period.

Table 3

Data from 1990 running period.

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Measurement of the production rates of eta and eta-prime in hadronic Z decays

The ALEPH collaboration Buskulic, D. ; Decamp, D. ; Goy, C. ; et al.

Phys.Lett.B 292 (1992) 210-220, 1992.

Inspire Record 334575 DOI 10.17182/hepdata.29156

The decays η → γγ and η ′ → ηπ + π − have been observed in hadronic decays of the Z produced at LEP. The fragmentation functions of both the η and η ′ have been measured. The measured multiplicities for x > 0.1 are 0.298±0.023±0.021 and 0.068±0.016 for η and η ′ respectively. While the fragmentation function for the η is fairly well described by the JETSET Monte Carlo, it is found that the production rate of the η ′ is a factor of four less than the corresponding prediction.

3 data tables match query

Table 1

No description provided.

Table 2

Additional 7 pct systematic error.

Table 3

Additional 23 pct systematic error.

Measurement of the D*+- cross-section in two photon collisions at LEP

The ALEPH collaboration Buskulic, D. ; Casper, D. ; De Bonis, I. ; et al.

Phys.Lett.B 355 (1995) 595-605, 1995.

Inspire Record 394752 DOI 10.17182/hepdata.47950

The inclusive production of D ∗± mesons in photon-photon collisions has been measured by the Aleph experiment at LEP with a beam energy of 45 GeV. The D ∗+ are detected in their decay to D 0 π + with the D 0 observed in three separate decay modes: (1) K − π + , (2) K − π + π 0 and (3) K − π + π − π + , and analagously for the D ∗− modes. A total of 33 events was observed from an integrated luminosity of 73 pb −1 which corresponds to a cross section for Σ( e + e − → e + e − D ∗± X ) of 155 ± 33 ± 21 pb. This result is compatible with both the direct production γγ → c c in the Born approximation and with a more complete calculation which includes both radiative QCD corrections and contributions in which one of the photons is first resolved into its quark and gluon constituents. The shapes of distributions for events containing a D ∗+ are found to be better described by the latter.

1 data table match query

Table 1

No description provided.

Search for supersymmetry in the photon(s) plus missing energy channels at s**(1/2) = 161-GeV and 172-GeV.

The ALEPH collaboration Barate, R. ; Buskulic, D. ; Decamp, D. ; et al.

Phys.Lett.B 420 (1998) 127-139, 1998.

Inspire Record 449077 DOI 10.17182/hepdata.47381

Searches for supersymmetric particles in channels with one or more photons and missing energy have been performed with data collected by the ALEPH detector at LEP. The data consist of 11.1 pb-1 at $\sqrt{s} = 161 GeV$, 1.1 pb-1 at 170 GeV and 9.5 pb-1 at 172 GeV. The e+e- -> nunu+photon cross section is measured. The data are in good agreement with predictions based on the Standard Model, and are used to set upper limits on the cross sections for anomalous photon production. These limits are compared to two different SUSY models and used to set limits on the neutralino mass. A limit of 71 GeV/c^2 at 95% C.L. is set on the mass of the lightest neutralino ($\tau_{\chi_{1}^{0}} \leq $ 3 ns) for the gauge-mediated supersymmetry breaking and LNZ models.

1 data table match query

Table 1

No description provided.

Measurement of the W pair cross section in e+ e- collisions at 172-GeV.

The ALEPH collaboration Barate, R. ; Buskulic, D. ; Decamp, D. ; et al.

Phys.Lett.B 415 (1997) 435-444, 1997.

Inspire Record 446940 DOI 10.17182/hepdata.47408

The e + e − → W + W − cross section is measured in a data sample collected by ALEPH at a mean centre-of-mass energy of 172.09 GeV, corresponding to an integrated luminosity of 10.65 pb −1 . Cross sections are given for the three topologies, fully leptonic, semi-leptonic and hadronic of a W-pair decay. Under the assumption that no other decay modes are present, the W-pair cross section is measured to be 11.7±1.2 (stat.) ±0.3 (syst.) pb . The existence of the triple gauge boson vertex of the Standard Model is clearly preferred by the data. The decay branching ratio of the W boson into hadrons is measured to be B(W→hadrons) =67.7±3.1 (stat.) ±0.7 (syst.) % , allowing a determination of the CKM matrix element | V cs |=0.98±0.14(stat.)±0.03(syst.).

2 data tables match query

Table 1

Cross sections for the different topologies.

Table 2

Combined W+ W- cross section.

Measurement of the W mass in e+ e- collisions at production threshold

The ALEPH collaboration Barate, R. ; Buskulic, D. ; Decamp, D. ; et al.

Phys.Lett.B 401 (1997) 347-362, 1997.

Inspire Record 441188 DOI 10.17182/hepdata.47488

In June 1996, the LEP centre-of-mass energy was raised to 161 GeV. Pair production of W bosons in e + e − collisions was observed for the first time by the LEP experiments. An integrated luminosity of 11 pb −1 was recorded in the ALEPH detector, in which WW candidate events were observed. In 6 events both Ws decay leptonically. In 16 events, one W decays leptonically, the other into hadrons. In the channel where both Ws decay into hadrons, a signal was separated from the large background by means of several multi-variate analyses. The W pair cross-section is measured to be σ WW = 4.23 ± 0.73 (stat.) ± 0.19 (syst.) pb. From this cross-section, the W mass is derived within the framework of the Standard Model: m W = 80.14 ± 0.34 (stat.) ± 0.09 (syst.) ± 0.03 (LEP energy) GeV/ c 2

1 data table match query

Table 1

No description provided.

Determination of the Number of Light Neutrino Species

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Lees, J.P. ; et al.

Phys.Lett.B 231 (1989) 519-529, 1989.

Inspire Record 282904 DOI 10.17182/hepdata.29758

The cross-section for e + e − → hadrons in the vicinity of the Z boson peak has been measured with the ALEPH detector at the CERN Large Electron Positron collider, LEP. Measurements of the Z mass, M z = (91.174±0.070) GeV, the Z width Γ z =(2.68±0.15) GeV, and of the peak hadronic cross-section, σ had peak =(29.3±1.2) nb, are presented. With the constraints of the standard electroweak model, the number of light neutrino species is found to be N v =3.27±0.30. this results rules out of the possibility of a fourth type of light neutrino at 98% CL.

2 data tables match query

Table 1

Selection from TPC tracks.

Table 2

Selection by calorimeters.

rivet Analysis
First measurement of the quark to photon fragmentation function

The ALEPH collaboration Buskulic, D. ; Casper, D. ; De Bonis, I. ; et al.

Z.Phys.C 69 (1996) 365-378, 1996.

Inspire Record 398193 DOI 10.17182/hepdata.12261

Earlier measurements at LEP of isolated hard photons in hadronic Z decays, attributed to radiation from primary quark pairs, have been extended in the ALEPH experiment to include hard photon productioninside hadron jets. Events are selected where all particles combine democratically to form hadron jets, one of which contains a photon with a fractional energyz≥0.7. After statistical subtraction of non-prompt photons, the quark-to-photon fragmentation function,D(z), is extracted directly from the measured 2-jet rate. By taking into account the perturbative contributions toD(z) obtained from anO(ααs) QCD calculation, the unknown non-perturbative component ofD(z) is then determined at highz. Provided due account is taken of hadronization effects nearz=1, a good description of the other event topologies is then found.

16 data tables match query

Table 1

2-jet events. Variable Z has been defined as E(gamma)/(E(gamma)+E(had)), where E(gamma) is the energy of the hard photon in 'photon-jet', E(had) is the energy of the rest hadrons in jet. Ycut is jet resolution parameter (see paper).

Table 2

Table 3

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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.

2 data tables match query

Table 1

Exlclusive analysis from events with hard ISR.

Table 2

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