Measurement of fiducial and differential $W^+W^-$ production cross-sections at $\sqrt{s}=$13 TeV with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Eur.Phys.J.C 79 (2019) 884, 2019.
Inspire Record 1734263 DOI 10.17182/hepdata.89225

A measurement of fiducial and differential cross-sections for $W^+W^-$ production in proton-proton collisions at $\sqrt{s}=$13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of $36.1$ fb$^{-1}$ is presented. Events with one electron and one muon are selected, corresponding to the decay of the diboson system as $WW\rightarrow e^{\pm}\nu\mu^{\mp}\nu$. To suppress top-quark background, events containing jets with a transverse momentum exceeding 35 GeV are not included in the measurement phase space. The fiducial cross-section, six differential distributions and the cross-section as a function of the jet-veto transverse momentum threshold are measured and compared with several theoretical predictions. Constraints on anomalous electroweak gauge boson self-interactions are also presented in the framework of a dimension-six effective field theory.

43 data tables

Measured fiducial cross-section as a function of the jet-veto $p_{T}$ threshold. The value at the jet-veto $p_{T}$ threshold of 35GeV corresponds to the nominal fiducial cross section measured in this publication.

Statistical correlation between bins in data for the measured fiducial cross-section as a function of the jet-veto $p_{T}$ threshold. The value at the jet-veto $p_{T}$ threshold of 35GeV corresponds to the nominal fiducial cross section measured in this publication.

Total correlation between bins in data for the measured fiducial cross-section as a function of the jet-veto $p_{T}$ threshold. The value at the jet-veto $p_{T}$ threshold of 35GeV corresponds to the nominal fiducial cross section measured in this publication.

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Version 2
Measurement of the $Z(\rightarrow\ell^+\ell^-)\gamma$ production cross-section in $pp$ collisions at $\sqrt{s} =13$ TeV with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abbott, Dale Charles ; et al.
JHEP 03 (2020) 054, 2020.
Inspire Record 1764342 DOI 10.17182/hepdata.89875

The production of a prompt photon in association with a $Z$ boson is studied in proton-proton collisions at a centre-of-mass energy $\sqrt{s} =$ 13 TeV. The analysis uses a data sample with an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector at the LHC from 2015 to 2018. The production cross-section for the process $pp \rightarrow \ell^+\ell^-\gamma+X$ ($\ell = e, \mu$) is measured within a fiducial phase-space region defined by kinematic requirements on the photon and the leptons, and by isolation requirements on the photon. An experimental precision of 2.9% is achieved for the fiducial cross-section. Differential cross-sections are measured as a function of each of six kinematic variables characterising the $\ell^+\ell^-\gamma$ system. The data are compared with theoretical predictions based on next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations. The impact of next-to-leading-order electroweak corrections is also considered.

14 data tables

The measured fiducial cross section. "Uncor" uncertainty includes all systematic uncertainties that are uncorrelated between electron and muon channels such as the uncertainty on the electron identification efficiency and the uncorrelated component of the background uncertainties. The parton-to-particle correction factor $C_{theory}$ is the ratio of the cross-section predicted by Sherpa LO samples at particle level within the fiducial phase-space region defined in Table 4 to the predicted cross-section at parton level within the same fiducial region but with the smooth-cone isolation prescription defined above replacing the particle-level photon isolation criterion, and with Born-level leptons in place of dressed leptons. This correction should be applied on fixed order parton-level calculations. The systematic uncertainty is evaluated from a comparison with the correction factor obtained using events generated with SHERPA 2.2.2 at NLO. In the case that the calculations are valid for dressed leptons, a modified correction factor excluding the Born-to-dressed lepton correction should be applied instead. This correction only takes into account the particle-level isolation criteria, and is provided separately here. The Sherpa 2.2.8 NLO cross-sections given below include a small contribution from EW $Z\gamma jj$ production of 4.57 fb.

The measured fiducial cross section. "Uncor" uncertainty includes all systematic uncertainties that are uncorrelated between electron and muon channels such as the uncertainty on the electron identification efficiency and the uncorrelated component of the background uncertainties. The parton-to-particle correction factor $C_{theory}$ is the ratio of the cross-section predicted by Sherpa LO samples at particle level within the fiducial phase-space region defined in Table 4 to the predicted cross-section at parton level within the same fiducial region but with the smooth-cone isolation prescription defined above replacing the particle-level photon isolation criterion, and with Born-level leptons in place of dressed leptons. This correction should be applied on fixed order parton-level calculations. The systematic uncertainty is evaluated from a comparison with the correction factor obtained using events generated with Sherpa 2.2.2 at NLO. In the case that the calculations are valid for dressed leptons, a modified correction factor excluding the Born-to-dressed lepton correction should be applied instead. This correction only takes into account the particle-level isolation criteria, and is provided separately here. The Sherpa 2.2.8 NLO cross-sections given below include a small contribution from EW $Z\gamma jj$ production of 4.57 fb.

The measured fiducial cross section vs $E_{\mathrm{T}}^\gamma$. The central values are provided along with the statistical and systematic uncertainties together with the sign information. The statistical and "Uncor" uncertainty should be treated as uncorrelated bin-to-bin, while the rest are correlated between bins, and they are written as signed NP variations. The parton-to-particle correction factor $C_{theory}$ is the ratio of the cross-section predicted by Sherpa LO samples at particle level within the fiducial phase-space region defined in Table 4 to the predicted cross-section at parton level within the same fiducial region but with the smooth-cone isolation prescription defined above replacing the particle-level photon isolation criterion, and with Born-level leptons in place of dressed leptons. This correction should be applied on fixed order parton-level calculations. The systematic uncertainty is evaluated from a comparison with the correction factor obtained using events generated with SHERPA 2.2.2 at NLO. In the case that the calculations are valid for dressed leptons, a modified correction factor excluding the Born-to-dressed lepton correction should be applied instead. This correction only takes into account the particle-level isolation criteria, and is provided separately here. The Sherpa 2.2.8 NLO cross-sections given below include a small contribution from EW $Z\gamma jj$ production.

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Dijet production in $\sqrt{s}=7$ TeV $pp$ collisions with large rapidity gaps at the ATLAS experiment

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Lett.B 754 (2016) 214-234, 2016.
Inspire Record 1402356 DOI 10.17182/hepdata.70762

A $6.8 \ {\rm nb^{-1}}$ sample of $pp$ collision data collected under low-luminosity conditions at $\sqrt{s} = 7$ TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with $p_\mathrm{T} > 20$ GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in $\Delta\eta^F$, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, $\tilde{\xi}$, of the fractional momentum loss of the proton assuming single diffractive dissociation ($pp \rightarrow pX$). Model comparisons indicate a dominant non-diffractive contribution up to moderately large $\Delta\eta^F$ and small $\tilde{\xi}$, with a diffractive contribution which is significant at the highest $\Delta\eta^F$ and the lowest $\tilde{\xi}$. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions.

6 data tables

The cross section differential in the forward rapidity gap size, DELTA(C=RAPGAP), for events with at least two jets of pt > 20 GeV found by the anti-kt jet algorithm with R=0.6.

The cross section differential in the forward rapidity gap size, DELTA(C=RAPGAP), for events with at least two jets of pt > 20 GeV found by the anti-kt jet algorithm with R=0.4.

The cross section differential in the fraction of the proton four-momentum carried by the Pomeron, LOG10(C=XI), for events with at least two jets of pt > 20 GeV found by the anti-kt jet algorithm with R=0.6.

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$Z$ boson production in $p+$Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV measured with the ATLAS detector

The ATLAS collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Rev.C 92 (2015) 044915, 2015.
Inspire Record 1384272 DOI 10.17182/hepdata.69247

The ATLAS Collaboration has measured the inclusive production of $Z$ bosons via their decays into electron and muon pairs in $p+$Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV at the Large Hadron Collider. The measurements are made using data corresponding to integrated luminosities of 29.4 nb$^{-1}$ and 28.1 nb$^{-1}$ for $Z \rightarrow ee$ and $Z \rightarrow \mu\mu$, respectively. The results from the two channels are consistent and combined to obtain a cross section times the $Z \rightarrow \ell\ell$ branching ratio, integrated over the rapidity region $|y^{*}_{Z}|<3.5$, of 139.8 $\pm$ 4.8 (stat.) $\pm$ 6.2 (syst.) $\pm$ 3.8 (lumi.) nb. Differential cross sections are presented as functions of the $Z$ boson rapidity and transverse momentum, and compared with models based on parton distributions both with and without nuclear corrections. The centrality dependence of $Z$ boson production in $p+$Pb collisions is measured and analyzed within the framework of a standard Glauber model and the model's extension for fluctuations of the underlying nucleon-nucleon scattering cross section.

7 data tables

The centrality bias factors derived from data as explained in the text. Model calculations shown in the Figure are found in arXiv:1412.0976.

The differential $Z$ boson production cross section, $d\sigma/dy^\mathrm{*}_{Z}$, as a function of $Z$ boson rapidity in the center-of-mass frame $y^\mathrm{*}_{Z}$, for $Z\rightarrow ee$, $Z\rightarrow\mu\mu$, and their combination $Z\rightarrow\ell\ell$.

The differential cross section of $Z$ boson production multiplied by the Bjorken $x$ of the parton in the lead nucleus, $x_{Pb} d\sigma /dx_{Pb}$, as a function of $x_{Pb}$.

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Version 2
Measurement of differential cross sections and $W^+/W^-$ cross-section ratios for $W$ boson production in association with jets at $\sqrt{s}=8$ TeV with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 05 (2018) 077, 2018.
Inspire Record 1635273 DOI 10.17182/hepdata.80076

This paper presents a measurement of the $W$ boson production cross section and the $W^{+}/W^{-}$ cross-section ratio, both in association with jets, in proton--proton collisions at $\sqrt{s}=8$ TeV with the ATLAS experiment at the Large Hadron Collider. The measurement is performed in final states containing one electron and missing transverse momentum using data corresponding to an integrated luminosity of 20.2 fb$^{-1}$. Differential cross sections for events with one or two jets are presented for a range of observables, including jet transverse momenta and rapidities, the scalar sum of transverse momenta of the visible particles and the missing transverse momentum in the event, and the transverse momentum of the $W$ boson. For a subset of the observables, the differential cross sections of positively and negatively charged $W$ bosons are measured separately. In the cross-section ratio of $W^{+}/W^{-}$ the dominant systematic uncertainties cancel out, improving the measurement precision by up to a factor of nine. The observables and ratios selected for this paper provide valuable input for the up quark, down quark, and gluon parton distribution functions of the proton.

86 data tables

Cross section for the production of W bosons for different inclusive jet multiplicities.

Statistical correlation between bins in data for the cross section for the production of W bosons for different inclusive jet multiplicities.

Differential cross sections for the production of W<sup>+</sup> bosons, W<sup>-</sup> bosons and the W<sup>+</sup>/W<sup>-</sup> cross section ratio as a function of the inclusive jet multiplicity.

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A Study of K0(s) production in Z0 decays

The OPAL collaboration Alexander, G. ; Allison, J. ; Allport, P.P. ; et al.
Phys.Lett.B 264 (1991) 467-475, 1991.
Inspire Record 316151 DOI 10.17182/hepdata.29375

The production of K 0 mesons in e + e − interactions at center of mass energies in the region of the Z 0 mass has been investigated with the OPAL detector at LEP. The rate is found to be 2.10±0.02±0.14 K 0 , Z 0 per hadronic event. The predictions from the JETSET and HERWIG generators agree very well with both the rate and the scale invariant cross section (1/σ had β) (dσ/d x E ) for K 0 production. Comparisons of the inclusive momentum spectrum with predictions of an analytical QCD formula and with data from lower center of mass energies are presented.

3 data tables

No description provided.

No description provided.

K0 multiplicity per hadronic event.


A Measurement of K*+- (892) production in hadronic Z0 decays

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, John ; et al.
Phys.Lett.B 305 (1993) 407-414, 1993.
Inspire Record 342766 DOI 10.17182/hepdata.28930

Measurements are presented of the inclusive cross section for K ∗ (892) ± production in hadronic decays of the Z 0 using a sample of about half a million events recorded with the OPAL experiment at LEP. Charged K ∗ mesons are reconstructed in the decay channel K 0 S π ± . A mean rate of 0.72±0.02±0.08 K ∗ mesons per hadronic event is found. Comparison of the results with predictions of the JETSET and HERWIG models shows that JETSET overestimates the K ∗± production cross section while HERWIG is consistent with the data.

2 data tables

No description provided.

No description provided.


A Measurement of strange baryon production in hadronic Z0 decays

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 291 (1992) 503-518, 1992.
Inspire Record 336771 DOI 10.17182/hepdata.29036

The production of the octet and decuplet baryons Λ, Ξ − , Σ (1385) ± , Ξ(1530) 0 and Ω − and the corresponding antibaryons has been measured in a sample of 485 000 hadronic Z 0 decays. Results on differential and integrated cross sections are presented. The differential cross section of Λ baryons is found to be softer than the one predicted by the Jetset and Herwig Monte Carlo generators. The measured decuplet yields are found to disagree with the simple diquark picture where only one tuning parameter for spin 1 diquarks is used. Comparisons of the momentum spectra for Λ and Ξ − with the predictions of an analytical QCD formula are also presented.

13 data tables

No description provided.

No description provided.

No description provided.

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Inclusive neutral vector meson production in hadronic Z0 decays

The OPAL collaboration Acton, P.D. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 56 (1992) 521-536, 1992.
Inspire Record 336772 DOI 10.17182/hepdata.14530

Results are reported of a study of neutral vector meson production in multihadronicZ0 decays in the OPAL experiment at LEP. Pions and kaons have been identified by specific ionisation energy loss andK±π∓ andK+K− mass spectra have been fitted, in bins of the scaled momentum variablexp, to combinations of resonance signals and non-resonant backgrounds. Rates are given forK*(892)° and ø(1020), and production cross sections are compared to the predictions of Monte Carlo models. Overall multiplicities have been determined as 0.76±0.07±0.06K*(892)° and 0.086±0.015±0.010 ø(1020) per hadronicZ0 decay (the quoted errors are respectively statistical and systematic). Momentum dependent distortions of the ππ mass spectra, possibly associated indirectly with Bose-Einstein effects, have prevented reliable measurement of the ρ(770)° cross section in this study.

4 data tables

No description provided.

No description provided.

No description provided.

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Measurement of the hadronic cross-section for the scattering of two virtual photons at LEP.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 24 (2002) 17-31, 2002.
Inspire Record 563730 DOI 10.17182/hepdata.48895

The interaction of virtual photons is investigated using the reaction e+e- -> e+e- hadrons based on data taken by the OPAL experiment at e+e- centre-of-mass energies sqrt(s_ee)=189-209 GeV, for W>5 GeV and at an average Q^2 of 17.9 GeV^2. The measured cross-sections are compared to predictions of the Quark Parton Model (QPM), to the Leading Order QCD Monte Carlo model PHOJET to the NLO prediction for the reaction e+e- -> e+e-qqbar, and to BFKL calculations. PHOJET, NLO e+e- -> e+e-qqbar, and QPM describe the data reasonably well, whereas the cross-section predicted by a Leading Order BFKL calculation is too large.

11 data tables

Total cross section in the given phase space and assuming ALPHA = 1/137.

Differential cross section as a function of X where X is the maximum value of X1 or X2, the upper and lower vertex values.

Differential cross section as a function of Q**2 where Q**2 is the maximum value of Q1**2 or Q2**2, the upper and lower vertex values.

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Di-jet production in photon photon collisions at s(ee)**(1/2) = from 189-GeV to 209-GeV.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 31 (2003) 307-325, 2003.
Inspire Record 611415 DOI 10.17182/hepdata.49662

Di-jet producion is studied in collisions of quasi-real photons at e+e- centre- of-mass energies sqrt(s)ee from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are reconstructed using an inclusive k_t clustering algorithm for all cross-section measurements presented. A cone jet algorithm is used in addition to study the different structure of the jets resulting from either of the algorithms. The inclusive di-jet cross-section is measured as a function of the mean transverse energy Etm(jet) of the two leading jets, and as a functiuon of the estimated fraction of the photon momentum carried by the parton entering the hard sub-process, xg, for different regions of Etm (jet). Angular distribution in di-jet events are measured and used to demonstrate the dominance of quark and gluon initiated processes in different regions of phase space. Furthermore the inclusive di-jet cross-section as a function of |eta(jet)| and |delta eta (jet)| is presented where eta(jet) is the jet pseudo-rapidity. Different regions of the xg+ -xg- -space are explored to study and control the influence of an underlying event. The results are compared to next-to-leading order perturbative QCD calculations and to the predictions of the leading order Monte Carlo generator PYTHIA.

21 data tables

The di-jet cross section as a function of the angle between the jet and thedirection of the incoming parton in the centre-of-mass frame for the region whe re both X(C=GAMMA+) and X(C=GAMMA-) are > 0.75.

The di-jet cross section as a function of the angle between the jet and thedirection of the incoming parton in the centre-of-mass frame for the region whe re both X(C=GAMMA+) and X(C=GAMMA-) are < 0.75.

The di-jet cross section as a function of the mean transverse energy of thedi-jet system for the full X(C=GAMMA+) and X(C=GAMMA-) region.

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Measurement of the hadronic photon structure function F2(gamma) at LEP2.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Phys.Lett.B 533 (2002) 207-222, 2002.
Inspire Record 583115 DOI 10.17182/hepdata.49744

The hadronic structure of the photon F2gamma is measured as a function of Bjorken x and of the photon virtuality Q2 using deep-inelastic scattering data taken by the OPAL detector at LEP at e+e- centre-of-mass energies from 183 to 209 GeV. Previous OPAL measurements of the x dependence of F2gamma are extended to an average Q2 of <Q2>=780GeV2 using data in the kinematic range 0.15 < x < 0.98. The Q2 evolution of F2gamma is studied for 12.1 < <Q2> < 780GeV2 using three ranges of x. As predicted by QCD, the data show positive scaling violations in F2gamma for the central x region 0.10-0.60. Several parameterisations of F2gamma are in qualitative agreement with the measurements whereas the quark-parton model prediction fails to describe the data.

13 data tables

F2 and DSIG/DX for the EE sample in the high Q**2 region as a function of X.

Statistical correlations between the bins in the preceding table.

The measured value of F2 and DSIG/DX for the SW data sample in the Q**2 range 9 to 15 GeV**2.

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The Production of neutral kaons in Z0 decays and their Bose-Einstein correlations

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 67 (1995) 389-402, 1995.
Inspire Record 393503 DOI 10.17182/hepdata.48008

The production of neutral kaons in e+e− annihilation at centre-of-mass energies in the region of the Z0 mass and their Bose-Einstein correlations are investigated with the OPAL detector at LEP. A total of about 1.26×106 Z0 hadronic decay events are used in the analysis. The production rate of K0 mesons is found to be 1.99±0.01±0.04 per hadronic event, where the first error is statistical and the second systematic. Both the rate and the differential cross section for K0 production are compared to the predictions of Monte Carlo generators. This comparison indicates that the fragmentation is too soft in bothJetset andHerwig. Bose-Einstein correlations in Ks0Ks0 pairs are measured through the quantityQ, the four momentum difference of the pair. A threshold enhancement is observed in Ks0Ks0 pairs originating from a mixed sample of\(K^0 \bar K^0\) and K0K0 (\(\bar K^0 \bar K^0\)) pairs. For the strength of the effect and for the radius of the emitting source we find values of λ=1.14±0.23±0.32 andR0=(0.76±0.10±0.11) fm respectively. The first error is statistical and the second systematic.

3 data tables

No description provided.

The mean x is computed using the method of Lafferty and Wyatt NIM A355(1995)541.

The mean x is computed using the method of Lafferty and Wyatt NIM A355(1995)541.


Inclusive strange vector and tensor meson production in hadronic Z0 decays

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 68 (1995) 1-12, 1995.
Inspire Record 393954 DOI 10.17182/hepdata.47993

Measurements have been made in the OPAL experiment at LEP of the inclusive production of strange vector φ(1020) and K*(892)0 mesons, and the tensor meson K2*(1430)0. The overall production rates per hadronic Z0 decay have been determined to be 0.100±0.004stat.±0.007syst. φ(1020) mesons, 0.74±0.03stat.±0.03syst. K*(892)0 mesons and (forxE<0.3) 0.19±0.04stat.±0.06syst. K2*(1430)0 mesons. The measurements for the vector states update previously published results based on lower statistics, while the K2*(1430)0 rate represents the first direct measurement of a strange tensor state in Z0 decay. For the vector states, both the overall production rates and normalised differential cross sections, with respect to the scaled energy variablexE, have been compared to JETSET and HERWIG predictions. The peak positions in the ζ=ln(1/xp) distributions have been measured and compared to measurements of other hadron states.

5 data tables

No description provided.

No description provided.

Extrapolated to full x region.

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Inclusive analysis of the b quark fragmentation function in Z decays at LEP. ((B))

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 29 (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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Charged particle momentum spectra in e+ e- annihilation at s**(1/2) = 192-GeV - 209-GeV.

The OPAL collaboration Abbiendi, G. ; Ainsley, C. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 27 (2003) 467-481, 2003.
Inspire Record 595335 DOI 10.17182/hepdata.48893

Charged particle momentum distributions are studied in the reaction e+e- -> hadrons, using data collected with the OPAL detector at centre-of-mass energies from 192 GeV to 209 GeV. The data correspond to an average centre-of- mass energy of 201.7 GeV and a total integrated luminosity of 433 pb-1. The measured distributions and derived quantities, in combination with corresponding results obtained at lower centre-of-mass energies, are compared to QCD predictions in various theoretical approaches to study the energy dependence of the strong interaction and to test QCD as the theory describing it. In general, a good agreement is found between the measurements and the corresponding QCD predictions.

5 data tables

The measured values of the PTIN distribution.

The measured values of the PTOUT distribution.

The measured values of the rapidity, YRAP, distribution.

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QCD studies with e+ e- annihilation data at 172-GeV to 189-GeV.

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Akesson, P.F. ; et al.
Eur.Phys.J.C 16 (2000) 185-210, 2000.
Inspire Record 513476 DOI 10.17182/hepdata.49000

We have studied hadronic events from e+e- annihilation data at centre-of-mass energies of sqrt{s}=172, 183 and 189 GeV. The total integrated luminosity of the three samples, measured with the OPAL detector, corresponds to 250 pb^-1. We present distributions of event shape variables, charged particle multiplicity and momentum, measured separately in the three data samples. From these we extract measurements of the strong coupling alpha_s, the mean charged particle multiplicity <nch> and the peak position xi_0 in the xi_p=ln(1/x_p) distribution. In general the data are described well by analytic QCD calculations and Monte Carlo models. Our measured values of alpha_s, <nch> and xi_0 are consistent with previous determinations at sqrt{s}=MZ.

20 data tables

Distribution of Thrust.

Distribution of Thrust Major.

Distribution of Thrust Minor.

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Measurement of the longitudinal, transverse and asymmetry fragmentation functions at LEP

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 68 (1995) 203-214, 1995.
Inspire Record 395450 DOI 10.17182/hepdata.48040

The fragmentation function for the process e+e−→h+X, whereh represents a hadron, may be decomposed into transverse, longitudinal and asymmetric contributions by analysis of the distribution of polar production angles. A number of new tests of QCD have been proposed using these fragmentation functions, but so far no data have been published on the separate components. We have performed such a separation using data on charged particles from hadronic Z0 decays atOpal, and have compared the results with the predictions of QCD. By integrating the fragmentation functions, we determine the average charged particle multiplicity to be\(\overline {n_{ch} }= 21.05 \pm 0.20\). The longitudinal to total cross-section ratio is determined to be σL/σtot=0.057±0.005. From the longitudinal fragmentation function we are able to extract the gluon fragmentation function. The connection between the asymmetry fragmentation function and electroweak asymmetrics is discussed.

4 data tables

Transverse component of the fragmentation function.

Longitudinal component of the fragmentation function.

Asymmetry component of the fragmentation function.

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Delta++ production in hadronic Z0 decays

The OPAL collaboration Alexander, G. ; Allison, John ; Altekamp, N. ; et al.
Phys.Lett.B 358 (1995) 162-172, 1995.
Inspire Record 398320 DOI 10.17182/hepdata.48153

The production of Δ ++ baryons has been measured using 3.5 million hadronic Z 0 decays collected with the OPAL detector at LEP. The production rate and fragmentation function are presented. A total of 0.22 ± 0.04 ± 0.04 Δ ++ + ( Δ ) −− per hadronic Z 0 decay is observed. The fragmentation function is found to be softer than that predicted by the JETSET and HERWIG Monte Carlo event generators. With this measurement of Δ ++ production, at least one baryon of each strangeness level in the lightest baryon decuplet has now been measured at LEP.

1 data table

No description provided.


Sigma+, Sigma0 and Sigma- hyperon production in hadronic Z0 decays.

The OPAL collaboration Alexander, G. ; Allison, John ; Altekamp, N. ; et al.
Z.Phys.C 73 (1997) 587-600, 1997.
Inspire Record 421977 DOI 10.17182/hepdata.47948

The production rates of the $J_{P}={1⩈er 2}^{+}$ octet Σ baryons in hadronic Z0 decays have been measured using the OPAL detector at LEP. The inclusive production rates per hadronic Z0 decay of the three isospin states (including the respective antiparticle) have been separately measured for the first time: $άtrix {n_{Sigma^{+}}=0.099pm 0.008pm 0.013ŗ n_{Sigma^{0}}=0.071pm 0.012pm 0.013ŗ n_{Sigma^{-}}=0.083pm 0.006pm 0.009ŗ}$ where the first error is statistical and the second is systematic. Differential cross-sections are also presented for the Σ+ and Σ− and compared with JETSET and HERWIG predictions. Assuming full isospin symmetry, the average inclusive rate is: ${1⩈er 3}[n_{Sigma^{+}+Sigma^{0}+Sigma^{-}}]=0.084pm 0.005 ({⤪ stat.}) pm 0.008 ({⤪ syst.})$.

5 data tables

Differential cross section for SIGMA+ production.

Differential cross section for SIGMA- production.

No description provided.

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QCD studies with e+ e- annihilation data at 130-GeV and 136-GeV.

The OPAL collaboration Alexander, G. ; Allison, John ; Altekamp, N. ; et al.
Z.Phys.C 72 (1996) 191-206, 1996.
Inspire Record 418007 DOI 10.17182/hepdata.47564

We have studied hadronic events produced at LEP at centre-of-mass energies of 130 and 136 GeV. Distributions of event shape observables, jet rates, momentum spectra and multiplicities are presented and compared to the predictions of several Monte Carlo models and analytic QCD calculations. From fits of event shape and jet rate distributions to\({\mathcal{O}}(\alpha _s^2 ) + NLLA\) QCD calculations, we determineαs(133 GeV)=0.110±0.005(stat.)±0.009(syst.). We measure the mean charged particle multiplicity 〈nch〉=23.40±0.45(stat.) ±0.47(syst.) and the position ζ0 of the peak in the ζp = ln(1/xp) distribution ζ0=3.94±0.05(stat.)±0.11(syst.). These results are compared to lower energy data and to analytic QCD or Monte Carlo predictions for their energy evolution.

23 data tables

Determination of alpha_s.

Multiplicity and high moments.

Tmajor distribution.

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Strange baryon production in hadronic Z0 decays.

The OPAL collaboration Alexander, G. ; Allison, John ; Altekamp, N. ; et al.
Z.Phys.C 73 (1997) 569-586, 1997.
Inspire Record 421978 DOI 10.17182/hepdata.47777

The production of the $J^{P}={1⩈er 2}^{+}$ octet baryons Λ and Ξ−, the $J^{P}={3⩈er 2}^{+}$ decuplet baryons Σ(1385)±Ξ(1530)0, and Ω−, and the $J^{P}={3⩈er 2}^{-}$ orbitally excited state Λ(1520) has been measured in a sample of approximately 3.65 million hadronic Z0 decays. The integrated rates and the differential cross-sections as a function of xE, the scaled energy, are determined. The differential cross-sections of the Λ and Ξ− baryons are found to be softer than those predicted by both the JETSET and HERWIG Monte Carlo generators. The measured baryon yields are found to disagree with the simple diquark picture where only one tuning parameter for spin 1 diquarks is allowed. The yields are further compared with a thermodynamic model of hadron production which includes the production of orbitally excited mesons and baryons. The momentum spectra of Λ, Ξ−, Σ(1385)±Ξ(1530)0, and Λ(1520) are also compared to the predictions of an analytical QCD formula.

13 data tables

Differential cross section for LAMBDA production.

(1/LN(X)) distribution for LAMBDA production.

Differential cross section for XI- production.

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QCD studies with e+ e- annihilation data at 161-GeV.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 75 (1997) 193-207, 1997.
Inspire Record 440721 DOI 10.17182/hepdata.47487

We have studied hadronic events produced at LEP at a centre-of-mass energy of 161 GeV. We present distributions of event shape variables, jet rates, charged particle momentum spectra and multiplicities. We determine the strong coupling strength to be αs(161 GeV) = 0.101±0.005(stat.)±0.007(syst.), the mean charged particle multiplicity to be 〈nch〉(161 GeV) = 24.46 ± 0.45(stat.) ± 0.44(syst.) and the position of the peak in the ξp = ln(1/xp) distribution to be ξ0(161 GeV) = 4.00 ±0.03(stat.)±0.04(syst.). These results are compared to data taken at lower centre-of-mass energies and to analytic QCD or Monte Carlo predictions. Our measured value of αs(161 GeV) is consistent with other measurements of αs. Within the current statistical and systematic uncertainties, the PYTHIA, HERWIG and ARIADNE QCD Monte Carlo models and analytic calculations are in overall agreement with our measurements. The COJETS QCD Monte Carlo is in general agreement with the data for momentum weighted distributions like Thrust, but predicts a significantly larger charged particle multiplicity than is observed experimentally.

26 data tables

Determination of alpha_s.

Multiplicity and higher moments.

Thrust distribution.

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Spin alignment of leading K*(892)0 mesons in hadronic Z0 decays.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Phys.Lett.B 412 (1997) 210-224, 1997.
Inspire Record 447146 DOI 10.17182/hepdata.47440

Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A preference for occupation of the helicity zero state is observed at all scaled momentum x_p values above 0.3, with the matrix element rho_00 rising to 0.66 +/- 0.11 for x_p > 0.7. The values of the real part of the off-diagonal element rho_1-1 are negative at large x_p, with a weighted average value of -0.09 +/- 0.03 for x_p > 0.3, in agreement with new theoretical predictions based on Standard Model parameters and coherent fragmentation of the qq(bar) system from the Z^0 decay. All other helicity density matrix elements measured are consistent with zero over the entire x_p range. The K^*0 fragmentation function has also been measured and the total rate determined to be 0.74 +/- 0.02 +/- 0.02 K*(892)^0 mesons per hadronic Z^0 decay.

4 data tables

Inclusive K*= cross section.

Helicity density matrices elemnts.

Ratios of helicity density matrices elements.

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Production of f0(980), f2(1270) and Phi(1020) in hadronic Z0 decay.

The OPAL collaboration Ackerstaff, K. ; Alexander, G. ; Allison, John ; et al.
Eur.Phys.J.C 4 (1998) 19-28, 1998.
Inspire Record 467092 DOI 10.17182/hepdata.49558

Inclusive production of the f_0(980), f_2(1270) and \phi(1020) resonances has been studied in a sample of 4.3 million hadronic Z^0 decays from the OPAL experiment at LEP. A coupled channel analysis has been used for the f_0 in simultaneous fits to the resonances in inclusive \pi+\pi- and K+K- mass spectra. Fragmentation functions are reported for the three states. Total inclusive rates are measured to be 0.141 +/- 0.007 +/- 0.011 f_0, 0.155 +/- 0.011 +/- 0.018 f_2, and 0.091 +/- 0.002 +/- 0.003 \phi mesons per hadronic Z^0 decay. The production properties of the f_0, including those in three-jet events, are compared with those of the f_2 and \phi, and with the Lund string model of hadron production. All measurements are consistent with the hypothesis that the f_0 is a conventional qq(bar) scalar meson.

2 data tables

Total inclusive production rates.

Fragmentation functions. Additional systematic errors of 7.6 PCT for F0, 11.6 PCT for F2 and 3.5 PCT for PHI. The uncorrelated systematic errors for F0 and F2 are negligible in comparison to the other errors.