Scaling violations of quark and gluon jet fragmentation functions in e+ e- annihilations at s**(1/2) = 91.2-GeV and 183-GeV to 209-GeV

The OPAL collaboration
Eur.Phys.J. C37 (2004) 25-47, 2004.
Inspire Record 648738 DOI 10.17182/hepdata.74689

Flavour inclusive, udsc and b fragmentation functions in unbiased jets, and flavour inclusive, udsc, b and gluon fragmentation functions in biased jets are measured in e+e- annihilations from data collected at centre-of-mass energies of 91.2, and 183-209 GeV with the OPAL detector at LEP. The unbiased jets are defined by hemispheres of inclusive hadronic events, while the biased jet measurements are based on three-jet events selected with jet algorithms. Several methods are employed to extract the fragmentation functions over a wide range of scales. Possible biases are studied in the results are obtained. The fragmentation functions are compared to results from lower energy e+e- experiments and with earlier LEP measurements and are found to be consistent. Scaling violations are observed and are found to be stronger for the fragmentation functions of gluon jets than for those of quarks. The measured fragmentation functions are compared to three recent theoretical next-to-leading order calculations and to the predictions of three Monte Carlo event generators. While the Monte Carlo models are in good agreement with the data, the theoretical predictions fail to describe the full set of results, in particular the b and gluon jet measurements.

11 data tables

The udsc jet fragmentation function in bins of $x_{\rm E}$ and scale. The scale denotes $Q_{\rm jet}$ for the biased jets and is given by the intervals, while it denotes $\sqrt{s}/2$ for the unbiased jets and is given by the single values. These data are displayed in Fig.7.

The b jet fragmentation function in bins of $x_{\rm E}$ and scale. The scale denotes $Q_{\rm jet}$ for the biased jets and is given by the intervals, while it denotes $\sqrt{s}/2$ for the unbiased jets and is given by the single values. These data are displayed in Fig. 8. In the region 0.48 $<x_{\rm E}<$ 0.90 and $Q_{\rm jet}=$ 30-70 GeV, no measurement was possible due to low statistics.

The gluon jet fragmentation functions in bins of $x_{\rm E}$ and scale $Q_{\rm jet}$ obtained from the biased jets using the b-tag method (BT). These data are displayed in Fig. 9. In the region 0.48 $<x_{\rm E}<$ 0.90 and $Q_{\rm jet}=$ 30-42 GeV for the b-tag method, no measurement was possible due to low statistics.

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Experimental studies of unbiased gluon jets from $e^{+} e^{-}$ annihilations using the jet boost algorithm

The OPAL collaboration
Phys.Rev. D69 (2004) 032002, 2004.
Inspire Record 631361 DOI 10.17182/hepdata.74246

We present the first experimental results based on the jet boost algorithm, a technique to select unbiased samples of gluon jets in e+e- annihilations, i.e. gluon jets free of biases introduced by event selection or jet finding criteria. Our results are derived from hadronic Z0 decays observed with the OPAL detector at the LEP e+e- collider at CERN. First, we test the boost algorithm through studies with Herwig Monte Carlo events and find that it provides accurate measurements of the charged particle multiplicity distributions of unbiased gluon jets for jet energies larger than about 5 GeV, and of the jet particle energy spectra (fragmentation functions) for jet energies larger than about 14 GeV. Second, we apply the boost algorithm to our data to derive unbiased measurements of the gluon jet multiplicity distribution for energies between about 5 and 18 GeV, and of the gluon jet fragmentation function at 14 and 18 GeV. In conjunction with our earlier results at 40 GeV, we then test QCD calculations for the energy evolution of the distributions, specifically the mean and first two non-trivial normalized factorial moments of the multiplicity distribution, and the fragmentation function. The theoretical results are found to be in global agreement with the data, although the factorial moments are not well described for jet energies below about 14 GeV.

5 data tables

The charged particle multiplicity distribution of gluon jets, $n_{\rm gluon}^{\rm ch.}$, for $E_{\rm g}^*$$\,=\,$5.25, 5.98 and 6.98 GeV. The data have been corrected for detector acceptance and resolution, for event selection, and for gluon jet impurity.

The charged particle multiplicity distribution of gluon jets, $n_{\rm gluon}^{\rm ch.}$, for $E_{\rm g}^*$$\,=\,$8.43 and 10.92 GeV. The data have been corrected for detector acceptance and resolution, for event selection, and for gluon jet impurity.

The charged particle multiplicity distribution of gluon jets, $n_{\rm gluon}^{\rm ch.}$, for $E_{\rm g}^*$$\,=\,$14.24 and 17.72 GeV. The data have been corrected for detector acceptance and resolution, for event selection, and for gluon jet impurity.

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Measurement of observables sensitive to coherence effects in hadronic Z decays with the OPAL detector at LEP

The OPAL collaboration Fischer, Nadine ; Gieseke, Stefan ; Kluth, Stefan ; et al.
Eur.Phys.J. C75 (2015) 571, 2015.
Inspire Record 1367303 DOI 10.17182/hepdata.73695

A study of QCD coherence is presented based on a sample of about 397,000 $e^{+}e^{-}$ hadronic annihilation events collected at $\sqrt{s}=91$  GeV with the OPAL detector at LEP. The study is based on four recently proposed observables that are sensitive to coherence effects in the perturbative regime. The measurement of these observables is presented, along with a comparison with the predictions of different parton shower models. The models include both conventional parton shower models and dipole antenna models. Different ordering variables are used to investigate their influence on the predictions.

14 data tables

The normalized corrected data at the hadron level for the emission angle $\theta_{14}$.

The correlation matrix of the normalized corrected data at the hadron level for the emission angle $\theta_{14}$.

The normalized corrected data at the hadron level for the mass ratio $\rho=M_L^2/M_H^2$.

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A Study of D*+- production in Z0 decays

The OPAL collaboration Alexander, G. ; Allison, J. ; Allport, P.P. ; et al.
Phys.Lett. B262 (1991) 341-350, 1991.
Inspire Record 315060 DOI 10.17182/hepdata.9272
2 data tables

FD denotes the fraction of D* mesons from primary charmed quarks, derived from the fit (see text).

No description provided.


Studies of strong and electroweak interactions using final state photon emission in hadronic Z0 decays

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, John ; et al.
Z.Phys. C58 (1993) 405-418, 1993.
Inspire Record 343181 DOI 10.17182/hepdata.52379
4 data tables

Corrected number of hadronc events that have a final state photon per 1000 multhadronic Z0 decays, using the E0 scheme.

Corrected number of hadronc events that have a final state photon per 1000 multhadronic Z0 decays, using the Durham scheme.

Corrected number of events that have a final state photon with 1, 2, 3, or more jets per 1000 multhadronic Z0 decays, using the E0 scheme.

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Inclusive Jet Production in Photon-Photon Collisions at s(ee)**(1/2) from 189 to 209-GeV

The OPAL collaboration
Phys.Lett. B658 (2008) 185-192, 2008.
Inspire Record 754316 DOI 10.17182/hepdata.48798

Inclusive jet production (e+e- -> e+e- +jet+X) is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies sqrt see from 189 to 209 GeV. Jets are reconstructed using the kp jet algorithm. The inclusive differential cross-section is measured as a function of the jet transverse momentum, ptjet, in the range 5 <ptjet < 40 GeV for pseudo-rapidities, etaj, in the range -1.5 < etaj < 1.5. The results are compared to predictions of perturbative QCD in next-to-leading order in the strong coupling constant.

2 data tables

Inclusive jet cross section for the absolute jet pseudorapidity < 1.0.

Inclusive jet cross section for the absolute jet pseudorapidity < 1.5.


Measurement of the e+ e- ---> W+ W- cross section and W decay branching fractions at LEP

The OPAL collaboration
Eur.Phys.J. C52 (2007) 767-785, 2007.
Inspire Record 757918 DOI 10.17182/hepdata.48533

From a total data sample of 701.1 pb^-1 recorded with e+e- centre-of-mass energies of sqrt = 161-209 GeV with the OPAL detector at LEP, 11693 W-pair candidate events are selected. These data are used to obtain measurements of the W-pair production cross sections at 10 different centre-of-mass energies. The ratio of the measured cross sections to the Standard Model expectation is found to be: data/SM = 1.002 +- 0.011(stat.) +- 0.007(syst.) +- 0.005(theory), where the uncertainties are statistical, experimental systematics and theory systematics respectively. The data are used to determine the W boson branching fractions, which are found to be consistent with lepton universality of the charged current interaction. Assuming lepton universality, the branching ratio to hadrons is determined to be 67.41 +- 0.37(stat.) +- 0.23(syst.)%, from which the CKM matrix element Vcs is determined to be 0.96+-0.017(stat.)+-0.012(syst.). The differential cross section as a function of the W^- production angle is measured for the qqev and qqmv final states. The results described in this paper are consistent with the expectations from the Standard Model.

5 data tables

Measured cross section for the (lepton nu lepton nu) decay mode.

Measured cross section for the (quark quark lepton nu) decay mode.

Measured cross section for the (quark quark quark quark) decay mode.

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Comparison of deep inelastic electron photon scattering data with the HERWIG and PHOJET Monte Carlo models

The ALEPH L3 OPAL LEP Working Group collaborations Achard, P. ; Andreev, V. ; Braccini, S. ; et al.
Eur.Phys.J. C23 (2002) 201-223, 2002.
Inspire Record 535230 DOI 10.17182/hepdata.49877

Deep inelastic electron-photon scattering is studied in the Q**2 range from 1.2 to 30 GeV**2 using the LEP1 data taken with the ALEPH, L3 and OPAL detectors at centre-of-mass energies close to the mass of the Z boson. Distributions of the measured hadronic final state are corrected to the hadron level and compared to the predictions of the HERWIG and PHOJET Monte Carlo models. For large regions in most of the distributions studied the results of the different experiments agree with one another. However, significant differences are found between the data and the models. Therefore the combined LEP data serve as an important input to improve on the Monte Carlo models.

11 data tables

The individual differential cross sections (DSIG/DW) in the low Q**2 regions for the three experiments.. The data are corrected using the HERWIG-kt model.

The combined differential cross sections (DSIG/DW) separately for the low and high Q**2 regions. The data are corrected using the HERWIG-kt model.

The combined differential cross sections (DSIG/DW) separately for the low and high Q**2 regions. The data are corrected using the PHOJET model.

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Inclusive production of charged hadrons in photon-photon collisions

The OPAL collaboration
Phys.Lett. B651 (2007) 92-101, 2007.
Inspire Record 734955 DOI 10.17182/hepdata.48554

The inclusive production of charged hadrons in the collisions of quasi-real photons e+e- -> e+e- +X has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass energies from 183 to 209 GeV. The differential cross-sections as a function of the transverse momentum and the pseudorapidity of the hadrons are compared to theoretical calculations of up to next-to-leading order (NLO) in the strong coupling constant alpha{s}. The data are also compared to a measurement by the L3 Collaboration, in which a large deviation from the NLO predictions is observed.

12 data tables

Differential inclusive charged hadron production cross section as a function of PT.

Differential inclusive charged hadron production cross section as a function of PT.

Differential inclusive charged hadron production cross section as a function of PT.

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Inclusive analysis of the b quark fragmentation function in Z decays at LEP

The OPAL collaboration
Eur.Phys.J. C29 (2003) 463-478, 2003.
Inspire Record 599181 DOI 10.17182/hepdata.43196

A study of b quark hadronisation is presented using inclusively reconstructed B hadrons in about four million hadronic Z decays recorded in 1992-2000 with the OPAL detector at LEP. The data are compared to different theoretical models, and fragmentation function parameters of these models are fitted. The average scaled energy of weakly decaying B hadrons is determined to be &lt;xe>=0.7193+-0.0016(stat)+0.0036-0.0031(syst)

4 data tables

No description provided.

Correlation matrix of statistical uncertainties.

Correlation matrix of positive systematic uncertainties.

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Measurement of event shape distributions and moments in e+ e- ---> hadrons at 91-GeV - 209-GeV and a determination of alpha(s)

The OPAL collaboration
Eur.Phys.J. C40 (2005) 287-316, 2005.
Inspire Record 669402 DOI 10.17182/hepdata.48652

We have studied hadronic events from e+e- annihilation data at centre-of-mass energies from 91 to 209 GeV. We present distributions of event shape observables and their moments at each energy and compare with QCD Monte Carlo models. From the event shape distributions we extract the strong coupling alpha_s and test its evolution with energy scale. The results are consistent with the running of alpha_s expected from QCD. Combining all data, the value of alpha_s(M_Z) is determined to be alpha_s(M_Z) = 0.1191 +- 0.0005 (stat.) +- 0.0010 (expt.) +- 0.0011 (hadr.) +- 0.0044 (theo.). The energy evolution of the moments is also used to determine a value of alpha_s with slightly larger errors: alpha_s(M_Z) = 0.1223 +- 0.0005 (stat.) +- 0.0014 (expt.) +- 0.0016 (hadr.) +0.0054 -0.0036 (theo.).

27 data tables

Measured normalized differential distribution for 1-THRUST.

Measured normalized differential distribution for HEAVY-JET-MASS.

Measured normalized differential distribution for C-PARAMETER.

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Study of Z pair production and anomalous couplings in e+ e- collisions at s**(1/2) between 190-GeV and 209-GeV

The OPAL collaboration
Eur.Phys.J. C32 (2003) 303-322, 2003.
Inspire Record 630099 DOI 10.17182/hepdata.49700

A study of Z-boson pair production in e+e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nn), quark and lepton pairs, (qql+l-, qqnn) and only hadrons (qqqq) are considered. In all states with at least one Z boson decaying hadronically, lifetime, lepton and event-shape tags are used to separate bb pairs from qq final state. Limits on anomalous ZZgamma and ZZZ couplings are derived from the measured cross sections and from event kinematics using an optimal observable method. Limits on low scale gravity with large dimensions are derived from the cross sections and their dependence on polar angle.

1 data table

The NC2 Z0-pair cross sections obtained from fits to the data.


W boson polarization at LEP2

The OPAL collaboration
Phys.Lett. B585 (2004) 223-236, 2004.
Inspire Record 635790 DOI 10.17182/hepdata.49660

Elements of the spin density matrix for W bosons in e+e- -> W+W- -> qqln events are measured from data recorded by the OPAL detector at LEP. This information is used calculate polarised differential cross-sections and to search for CP-violating effects. Results are presented for W bosons produced in e+e- collisions with centre-of-mass energies between 183 GeV and 209 GeV. The average fraction of W bosons that are longitudinally polarised is found to be (23.9 +- 2.1 +- 1.1)% compared to a Standard Model prediction of (23.9 +- 0.1)%. All results are consistent with CP conservation.

7 data tables

The fraction of longitudinal polarization for leptonically and hadronically decaying W bosons. The average values for all the centre of mass energies and for both lepton and hadron decay combined are also given.

The luminosity weighted average over all the centre of mass energies of the diagonal elements of the RHO++ and RHO-- SDM as a function of the cosine of the angle of the W- boson for the leptonic decay channel.

The luminosity weighted average over all the centre of mass energies of the diagonal element of the RHO00 SDM as a function of the cosine of the angle of the W- boson for both leptonic and hadronic decay channels, and combined.

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Tests of the standard model and constraints on new physics from measurements of fermion pair production at 189-GeV to 209-GeV at LEP

The OPAL collaboration
Eur.Phys.J. C33 (2004) 173-212, 2004.
Inspire Record 628491 DOI 10.17182/hepdata.43174

Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The measurements are used to determine the electromagnetic coupling constant alphaem at LEP2 energies. In addition, the results are used together with OPAL measurements at 91-183 GeV within the S-matrix formalism to determine the gamma-Z interference term and to make an almost model-independent measurement of the Z mass. Limits on extensions to the Standard Model described by effective four-fermion contact interactions or the addition of a heavy Z boson are also presented.

18 data tables

CM energy values.

Measured cross section for QUARK QUARKBAR (HADRON) production. The data are corrected to no interference between initial and final state radiation.

Measured cross section for MU+ MU- production. The data are corrected to no interference between initial and final state radiation.

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Search for trilinear neutral gauge boson couplings in $Z^-$ gamma production at $S^{(1/2)}$ = 189-GeV at LEP

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Ainsley, C. ; et al.
Eur.Phys.J. C17 (2000) 553-566, 2000.
Inspire Record 529897 DOI 10.17182/hepdata.49934

The data recorded at a centre-of-mass energy of 189GeV by the OPAL detector at LEP are used to search for trilinear couplings of the neutral gauge bosons in the process e+e- --> Z-gamma. The cross-sections are measured for multihadronic events with an energetic isolated photon and for events with a high energy photon accompanied by missing energy. These cross-sections and the photon energy, polar angle and isolation angle distributions are compared to the Standard Model predictions and to the theoretical expectations of a model allowing for Z-gamma-Z and Z-gamma-gamma vertices. Since no significant deviations with respect to the Standard Model expectations are found, constraints are derived on the strength of neutral trilinear gauge couplings.

2 data tables

Total sysytematic error for Q Qbar (NU NUbar) channel is 0.154 (0.048) pb.

See text for Z(GAMMA) anomalous coupling definitions. Statistical and systematic errors are combined in quadrature.


Measurement of $W$ boson polarizations and CP violating triple gauge couplings from $W^{+} W^{-}$ production at LEP

The OPAL collaboration
Eur.Phys.J. C19 (2001) 229-240, 2001.
Inspire Record 533112 DOI 10.17182/hepdata.49856

Measurements are presented of the polarisation of W+W- boson pairs produced in e+e- collisions, and of CP-violating WWZ and WWGamma trilinear gauge couplings. The data were recorded by the OPAL experiment at LEP during 1998, where a total integrated luminosity of 183 pb^-1 was obtained at a centre-of-mass energy of 189 GeV. The measurements are performed through a spin density matrix analysis of the W boson decay products. The fraction of W bosons produced with longitudinal polarisation was found to be sigma_L/sigma_total = (21.0 +- 3.3 +- 1.6)% where the first error is statistical and the second systematic. The joint W boson pair production fractions were found to be sigma_TT/sigma_total = (78.1 +- 9.0 +- 3.2) %, sigma_LL/sigma_total = (20.1 +- 7.2 +- 1.8) % and sigma_TL/sigma_total = (1.8 +- 14.7 +- 3.8) %. In the CP-violating trilinear gauge coupling sector we find kappa_z = -0.20 +0.10 -0.07, g^z_4 = -0.02 +0.32 -0.33 and lambda_z = -0.18 +0.24 -0.16, where errors include both statistical and systematic uncertainties. In each case the coupling is determined with all other couplings set to their Standard Model values except those related to the measured coupling via SU(2)_LxU(1)_Y symmetry. These results are consistent with Standard Model expectations.

4 data tables

Individual W-boson transverse polarised cross-sections.

Individual W-boson longitudinal polarised cross-sections.

W pair polarized cross-sections. (C=TT), (C=LL), and (C=TL) stand for both W transversely polarised, for both W longitudinally polarised, and for transversely and longitudinally polarisedW-bosons, respectively.

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Production rates of b anti-b quark pairs from gluons and b anti-b b anti-b events in hadronic Z0 decays

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Ainsley, C. ; et al.
Eur.Phys.J. C18 (2001) 447-460, 2001.
Inspire Record 535059 DOI 10.17182/hepdata.49875

The rates are measured per hadronic Z decay for gluon splitting to bb(bar) quark pairs, g_bb, and of events containing two bb(bar) quark pairs, g_4b, using a sample of four-jet events selected from data collected with the OPAL detector. Events with an enhanced signal of gluon splitting to bb(bar) quarks are selected if two of the jets are close in phase-space and contain detached secondary vertices. For the event sample containing two bb(bar) quark pairs, three of the four jets are required to have a significantly detached secondary vertex. Information from the event topology is combined in a likelihood fit to extract the values of g_bb and g_4b, namely g_bb = (3.07 +- 0.53(stat) +- 0.97(syst))x10^-3 g_4b = (0.36 +- 0.17(stat) +- 0.27(syst))x10^-3

1 data table

No description provided.


Measurement of |V(ub)| using b hadron semileptonic decay

The OPAL collaboration
Eur.Phys.J. C21 (2001) 399-410, 2001.
Inspire Record 559675 DOI 10.17182/hepdata.49835

The magnitude of the CKM matrix element Vub is determined by measuring the inclusive charmless semileptonic branching fraction of beauty hadrons at OPAL based on b -> Xu l nu event topology and kinematics. This analysis uses OPAL data collected between 1991 and 1995, which correspond to about four million hadronic Z decays. We measure Br(b -> Xu l) to be (1.63 +/- 0.53 +0.55/-0.62) x 10^(-3). The first uncertainty is the statistical error and the second is the systematic error. From this analysis, Vub is determined to be: |Vub| = (4.00 +/- 0.65(stat) +0.67/-0.76(sys) +/- 0.19(HQE)) x 10^(-3). The last error represents the theoretical uncertainties related to the extraction of |Vub| from Br(b -> Xu l) using the Heavy Quark Expansion.

1 data table

CKM is Cabibbo-Kobayashi-Maskawa (CKM) matrix element. The last DSYS error comes from the theoretical uncertainty.


Measurement of triple gauge boson couplings from $W^{+} W^{-}$ production at LEP energies up to 189-GeV

The OPAL collaboration
Eur.Phys.J. C19 (2001) 1-14, 2001.
Inspire Record 533113 DOI 10.17182/hepdata.49847

A measurement of triple gauge boson couplings is presented, based on W-pair data recorded by the OPAL detector at LEP during 1998 at a centre-of-mass energy of 189 GeV with an integrated luminosity of 183 pb^-1. After combining with our previous measurements at centre-of-mass energies of 161-183 GeV we obtain k_g=0.97 +0.20 -0.16, g_1^z=0.991 +0.060 -0.057 and lambda_g=-0.110 +0.058 -0.055, where the errors include both statistical and systematic uncertainties and each coupling is determined by setting the other two couplings to their SM values. These results are consistent with the Standard Model expectations.

1 data table

Triple gauge boson couplings. All systematic errors are added in quadrature.


Charged multiplicities in Z decays into u, d, and s quarks

The OPAL collaboration
Eur.Phys.J. C19 (2001) 257-268, 2001.
Inspire Record 536266 DOI 10.17182/hepdata.49812

About 4.4 million hadronic decays of Z bosons, recorded by the OPAL detector at LEP at a centre-of-mass energy of around sqrt(s) = 91.2 GeV, are used to determine the mean charged particle multiplicities for the three light quark flavours. Events from primary u, d, and s quarks are tagged by selecting characteristic particles which carry a large fraction of the beam energy. The charged particle multiplicities are measured in the hemispheres opposite to these particles. An unfolding procedure is applied to obtain these multiplicities for each primary light quark flavour. This yields <n_u> = 17.77 +- 0.51 +0.86 -1.20, <n_d> = 21.44 +- 0.63 +1.46 -1.17, <n_s> = 20.02 +- 0.13 +0.39 -0.37, where statistical and systematic errors are given. The results for <n_u> and <n_d> are almost fully statistically anti-correlated. Within the errors the result is consistent with the flavour independence of the strong interaction for the particle multiplicities in events from the light up, down, and strange quarks.

2 data tables

No description provided.

No description provided.


Search for lepton flavor violation in e+ e- collisions at s**(1/2) = 189-GeV - 209-GeV

The OPAL collaboration
Phys.Lett. B519 (2001) 23-32, 2001.
Inspire Record 562543 DOI 10.17182/hepdata.49819

We search for lepton flavour violating events (e mu, e tau and mu tau) that could be directly produced in e+e- annihilations, using the full available data sample collected with the OPAL detector at centre-of-mass energies between 189 GeV and 209 GeV. In general, the Standard Model expectations describe the data well for all the channels and at each sqrt(s). A single e mu event is observed where according to our Monte Carlo simulations only 0.019 events are expected from Standard Model processes. We obtain the first limits on the cross-sections sigma(e+e- -> e mu, e tau and mu tau) as a function of sqrt(s) at LEP2 energies.

1 data table

No description provided.


A Simultaneous measurement of the QCD color factors and the strong coupling

The OPAL collaboration
Eur.Phys.J. C20 (2001) 601-615, 2001.
Inspire Record 552446 DOI 10.17182/hepdata.49851

Using data from e+e- annihilation into hadrons, taken with the OPAL detector at LEP at the Z pole between 1991 and 1995, we performed a simultaneous measurement of the colour factors of the underlying gauge group of the strong interaction, CF and CA, and the strong coupling, alpha(s). The measurement was carried out by fitting next-to-leading order perturbative predictions to measured angular correlations of 4-jet events together with multi-jet related variables. Our results, CA = 3.02 +/- 0.25 (stat.) +/- 0.49 (syst.), CF = 1.34 +/- 0.13 (stat.) +/- 0.22 (syst.), alpha(s)(M_Z) = 0.120 +/- 0.011 (stat.) +/- 0.020 (syst.), provide a test of perturbative QCD in which the only assumptions are non-abelian gauge symmetry and standard hadronization models. The measurements are in agreement with SU(3) expectations for CF and CA and the world average of alpha(s)(M_Z).

1 data table

CA, CF are the color factors for SU(N) group.


Photonic events with missing energy in e+ e- collisions at S**(1/2) = 189-GeV

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Ainsley, C. ; et al.
Eur.Phys.J. C18 (2000) 253-272, 2000.
Inspire Record 526776 DOI 10.17182/hepdata.49967

Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 189GeV using the OPAL detector at LEP. Results are presented for event topologies consistent with a single photon or with an acoplanar photon pair. Cross-section measurements are performed within the kinematic acceptance of each selection, and the number of light neutrino species is measured. Cross-section results are compared with the expectations from the Standard Model process e+e- to nu nubar + photon(s). No evidence is observed for new physics contributions to these final states. Upper limits are derived on sigma(e+e- to XY).BR(X to Y gamma) and sigma(e+e- to XX).BR**2(X to Y gamma) for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos (X=nu*, Y = nu), to neutralino production (X=neutralino_2, Y=neutralino_1) and to supersymmetric models in which X = neutralino_1 and Y = light gravitino. The case of macroscopic decay lengths of particle X is considered for e+e- to XX, X to Y gamma, when M_Y is of order zero. The single-photon results are also used to place upper limits on superlight gravitino pair production as well as graviton-photon production in the context of theories with additional space dimensions.

1 data table

No description provided.


Measurement of the branching ratio for D(s)- ---> tau- anti-nu(tau) decays

The OPAL collaboration
Phys.Lett. B516 (2001) 236-248, 2001.
Inspire Record 553945 DOI 10.17182/hepdata.49836

Using about 3.9 million hadronic Z decays from e+e- collisions recorded by the OPAL detector at LEP at centre-of-mass energies near MZ the branching ratio for the decay D_s -> tau nu_tau has been measured to be (7.0 +/- 2.1(stat) +/- 2.0 (syst))%. This result can be used to derive the decay constant of the D_s meson: f(D_s) = 286 +/- 44(stat) +/- 41(syst) MeV.

1 data table

FORMFACTOR(NAME=FP,C=DECAY CONSTANT) is pseudoscalar meson decay constant.


Measurement of the branching ratio for the process b ---> tau- anti-nu(tau) X

The OPAL collaboration
Phys.Lett. B520 (2001) 1-10, 2001.
Inspire Record 561580 DOI 10.17182/hepdata.49743

The inclusive branching ratio for the process b -> tau nu X has been measured using hadronic Z decays collected by the OPAL experiment at LEP in the years 1992-2000. The result is: BR(b -> tau nu X) = (2.78 +/- 0.18 +/- 0.51)% This measurement is consistent with the Standard Model expectation and puts a constraint of tan(beta) / M(H+/-) < 0.53 GeV-1 at the 95% confidence level on Type II Two Higgs Doublet Models.

1 data table

TAN(BETA) is the two-Higgs-doublet model parameter, while M_H is the mass of charged Higgs.