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1Latest Papers from Table of Contents or Articles in PressB. Chalhoub ; F. Denoeud ; S. Liu ; I. A. Parkin ; H. Tang ; X. Wang ; J. Chiquet ; H. Belcram ; C. Tong ; B. Samans ; M. Correa ; C. Da Silva ; J. Just ; C. Falentin ; C. S. Koh ; I. Le Clainche ; M. Bernard ; P. Bento ; B. Noel ; K. Labadie ; A. Alberti ; M. Charles ; D. Arnaud ; H. Guo ; C. Daviaud ; S. Alamery ; K. Jabbari ; M. Zhao ; P. P. Edger ; H. Chelaifa ; D. Tack ; G. Lassalle ; I. Mestiri ; N. Schnel ; M. C. Le Paslier ; G. Fan ; V. Renault ; P. E. Bayer ; A. A. Golicz ; S. Manoli ; T. H. Lee ; V. H. Thi ; S. Chalabi ; Q. Hu ; C. Fan ; R. Tollenaere ; Y. Lu ; C. Battail ; J. Shen ; C. H. Sidebottom ; A. Canaguier ; A. Chauveau ; A. Berard ; G. Deniot ; M. Guan ; Z. Liu ; F. Sun ; Y. P. Lim ; E. Lyons ; C. D. Town ; I. Bancroft ; J. Meng ; J. Ma ; J. C. Pires ; G. J. King ; D. Brunel ; R. Delourme ; M. Renard ; J. M. Aury ; K. L. Adams ; J. Batley ; R. J. Snowdon ; J. Tost ; D. Edwards ; Y. Zhou ; W. Hua ; A. G. Sharpe ; A. H. Paterson ; C. Guan ; P. Wincker
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-08-26Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Brassica napus/cytology/*genetics ; *Chromosome Duplication ; *Evolution, Molecular ; *Genome, Plant ; *Polyploidy ; Seeds/*geneticsPublished by: -
2Latest Papers from Table of Contents or Articles in PressStaff View
Publication Date: 2018-08-17Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyGeosciencesComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Botany, Ecology, Online OnlyPublished by: -
3Articles: DFG German National LicensesAkrawy, M. Z. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Armitage, J. C. ; Arnison, G. T. J. ; Ashton, P. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bethke, S. ; Biebel, O. ; Binder, U. ; Bloodworth, I. J. ; Bock, P.
Springer
Published 1991Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Jet production rates in hadronicZ 0 decays are studied using four different recombination schemes to define resolvable jets. The strong coupling constant α s ( $$M_{Z^0 } $$ ) is determined in fits of the correspondingO(α s 2 ) QCD calculations to the differential 2-jet distributionsD 2(y). Hadronisation corrections and renormalisation scale uncertainties are found to be different for each recombination scheme. Within their overall systematic uncertainties, the four schemes yield consistent values of α s ( $$M_{Z^0 } $$ ), leading to a final result of $$\alpha _s (M_{Z^0 } ) = 0.118 \pm 0.008.$$ . The error includes the experimental uncertainties (±0.003), uncertainties of hadronisation corrections and of the degree of parton virtualities to which the data are corrected, as well as the uncertainty of choosing the renormalisation scale.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesActon, P. D. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Ashton, P. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Berlich, P. ; Bethke, S.
Springer
Published 1992Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract We present an analysis of multiplicity distributions of charged particles produced inZ 0 hadronic decays. The results are based on the analysis of 82941 events collected within 100 MeV of theZ 0 peak energy with the OPAL detector at LEP. The charged particle multiplicity distribution, corrected for initial-state radiation and for detector acceptance and resolution, was found to have a mean 〈n ch〉=21.40±0.02(stat.)±0.43(syst.) and a dispersionD=6.49±0.02(stat.)±0.20(syst.). The shape is well described by the Lognormal and Gamma distributions. A negative binomial parameterisation was found to describe the shape of the multiplicity distribution less well. A comparison with results obtained at lower energies confirms the validity of KNO(-G) scaling up to LEP energies. A separate analysis of events with low sphericity, typically associated with two-jet final states, shows the presence of features expected for models based on a stochastic production mechanism for particles. In all cases, the features observed in the data are well described by the Lund parton shower model JETSET.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesActon, P. D. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Ashton, P. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beaudion, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Berlich, P. ; Bethke, S.
Springer
Published 1992Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract The value of the strong coupling constant, $$\alpha _s (M_{Z^0 } )$$ , is determined from a study of 15 different observables in hadronicZ 0 and τ decays. The study includes global event shape variables, jet production rates, energy correlations, theZ 0 line shape and decay asymmetries and the hadronic branching fraction of τ-leptons. Differences between the αs values from the different observables can be consistently attributed to unknown higher order contributions to the calculations. These uncertaities may be parametrized by variations of the renormalization scale and of the parton virtuality to which the data are corrected, separately for each observable, resulting in a consistent description of the event shapes, jet rates and energy correlations with the value $$\alpha _s (M_{Z^0 } ) = 0.122_{ - 0.005}^{ + 0.006} $$ in . The error is dominated by the theoretical uncertainties. Application of recent calculations which include the resummation of leading and next-to-leading logarithms to all orders for some observables confirm this result with a reduced sensitivity to renormalization scale variations. TheZ 0 line shapes and τ-lepton branching ratios yield $$\alpha _s (M_{Z^0 } ) = 0.148 \pm 0.021$$ and $$\alpha _s (M_{Z^0 } ) = 0.123_{ - 0.007}^{ + 0.006} $$ , respectively, in . These measurements and their uncertainties are entirely independent of each other and from event shape and jet observables; the good agreement of the resulting αs values thus constitutes an important consistency check of the reliability of perturbative QCD.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesActon, P. D. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Berlich, P. ; Bethke, S. ; Biebel, O.
Springer
Published 1992Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Results are reported of a study of neutral vector meson production in multihadronicZ 0 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 variablex p , 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 hadronicZ 0 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.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesAkrawy, M. Z. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Armitage, J. C. ; Arnison, G. T. J. ; Ashton, P. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bethke, S. ; Biebel, O. ; Binder, U. ; Boodworth, I. J.
Springer
Published 1991Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract The OPAL detector at LEP is used to measure the branching ratio of theZ 0 into invisible particles by measuring the cross section of single photon events ine + e − collisions at centre-of-mass energies near theZ 0 resonance. In a data sample of 5.3 pb−1, we observe 73 events with single photons depositing more than 1.5 GeV in the electromagnetic calorimeter, with an expected background of 8±2 events not associated with invisibleZ 0 decay. With this data we determine theZ 0 invisible width to be 0.50±0.07±0.03 GeV, where the first error is statistical and the second systematic. This corresponds to 3.0±0.4±0.2 light neutrino generations in the Standard Model.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesActon, P. D. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahn, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P.
Springer
Published 1993Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract The cross section and jet rates ofZ 0 decays into photons and quarks are compared with matrix element Monte Carlos ofO(ααs). Good agreement is found between data and theoretical predictions. From the ratio of events with three jets plus a photon to those with two jets plus a photon, αs in first order is determined to be 0.176±0.010. Combining the cross section of final state photon events with the LEP average hadronic partial decay width of theZ 0, the widths of theZ 0 into up and down type quarks can be calculated. The results $$\begin{gathered} \Gamma _{u - type} = 242 \pm 46MeV; \hfill \\ \Gamma _{d - type} = 419 \pm 30MeV \hfill \\ \end{gathered} $$ are in good agreement with the standard model expectation. A comparison of the measured cross section as a function ofy cut with predictions of QCD shower models shows that, at the current level of accuracy ARIADNE and, to a lesser extent, HERWIG and JETSET can reproduce the measurement.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesActon, P. D. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P. ; Bethke, S.
Springer
Published 1993Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract The τ lifetime has been measured with the OPAL detector at LEP, from analyses using the impact parameters in decays to single charged tracks, and the decay lengths from τ decays to three charged tracks. The 1991 sample of approximately 12300 τ-pair events, of which 70% contain silicon microvertex detector information, has been combined with a re-analysis of the 5100 events recorded during 1990. The two statistically-independent determinations give: $$\begin{gathered} \tau (one - prong) = 296.4 \pm 7.1 (stat) \pm 3.8 (sys) fs, \hfill \\ \tau (three - prong) = 286.3 \pm 7.4 (stat) \pm 5.2 (sys) fs. \hfill \\ \end{gathered} $$ The weighted average of these results after combination of the uncorrelated systematic errors is: $$\tau _\tau = 291.9 \pm 5.1 (stat) \pm 3.1 (sys) fs.$$ .Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesAkers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Bartoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P.
Springer
Published 1994Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract A measurement of $$\Gamma _{b\bar b} /\Gamma _{had} \equiv \Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)$$ is presented using a “mixed tag” method involving the identification of $$Z^0 \to b\bar b$$ events by two different techniques. The first uses the large impact parameter of tracks emerging from the decay ofb-flavoured hadrons and the second their semi-leptonic decay. The identification efficiencies are measured from the data using all possible combinations of the two tags in opposite hemispheres. The method is therefore insensitive to Monte Carlo modelling of bottom quark production and ofb-flavoured hadron production and decay properties, and depends only weakly on the simulation of the detector. The data sample collected by OPAL at LEP in 1990 and 1991 is considered. The result is: $$\frac{{\Gamma _{b\bar b} }}{{\Gamma _{had} }} = 0.218 \pm 0.006(stat) \pm 0.007(syst) \pm 0.007(\Gamma _{c\bar c} /\Gamma _{had} ),$$ where the systematic uncertainty due to the charm quark partial width has been separated from the other systematic uncertainties. Combination with previous OPAL measurements gives: $$\frac{{\Gamma _{b\bar b} }}{{\Gamma _{had} }} = 0.220 \pm 0.004(stat) \pm 0.006(syst) \pm 0.006(\Gamma _{c\bar c} /\Gamma _{had} ),$$Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesAlexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Armitage, J. C. ; Ashton, P. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bethke, S. ; Biebel, O.
Springer
Published 1991Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Three-jet variables constructed from multi-hadronic events produced byZ 0 decays are compared to theoretical calculations assuming a vector gluon or a hypothetical scalar gluon. The data yield conclusive direct evidence for the former case. The distributions of the reduced energy of the second-most energetic jet and of the cosine of the Ellis-Karliner angle are chosen to demonstrate this effect.Type of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesAkers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Bartoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P.
Springer
Published 1993Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract From a sample of about 450 000 hadronicZ 0 decays, measurements of the average $$B^0 - \bar B^0 $$ mixing parameter, χ, the branching fraction ofZ 0 bosons into hadrons containing bottom quarks, $${{\Gamma (Z^0 \to b\bar b)} \mathord{\left/ {\vphantom {{\Gamma (Z^0 \to b\bar b)} {\Gamma (Z^0 \to hadrons)}}} \right. \kern-\nulldelimiterspace} {\Gamma (Z^0 \to hadrons)}}$$ , the average semileptonic branching ratios for such hadrons,B(b→l) andB(b→c→l), and the mean scaled energy of these hadrons, 〈xE〉, are presented. The measurements were obtained using a simultaneous fit to single-lepton and dilepton events collected with the OPAL detector at LEP, including both electrons and muons. The results are where the errors are statistical and systematic, respectively, in each case. The result forB)b→c→l) excludes decays of the typeb→→ℓ.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesActon, P. D. ; Akers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Batoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P.
Springer
Published 1993Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract A sample of 2610 electron candidates and 2762 muon candidates identified in hadronicZ 0 decays has been used to measure the averageb hadron lifetime. These data were recorded with the OPAL detector during 1990 and 1991. Maximum likelihood fits to the distributions of the lepton impact parameters yield an averageb hadron lifetime of $$\tau _b = 1523 \pm 34 \pm 38fs$$ , where the first error is statistical and the second systematic. This result is a weighted average over the semileptonic branching fractions and production rates of theb hadrons produced inZ 0 decays.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesAkers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Bartoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P.
Springer
Published 1993Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract We report on a measurement of the ratio of the strong coupling constants $$\alpha _s (M_{Z^0 } )$$ for various data samples with different quark flavour compositions obtained frome + e − annihilation at LEP. We select events with muons, electrons, andD *± mesons from charm and bottom decays, events with highly energeticK s 0 mesons originating predominantly from strange quarks, and events with highly energetic stable charged particles from a combination of up, down and strange quarks. From the jet production rates in these events we obtain from these samples the relative value of αs for the individual quark flavours as $$\begin{gathered} \frac{{\alpha _s^b }}{{\alpha _s^{udsc} }} = 1.017 \pm 0.036,\frac{{\alpha _s^c }}{{\alpha _s^{udsb} }} = 0.918 \pm 0.115, \hfill \\ \frac{{\alpha _s^s }}{{\alpha _s^{udcb} }} = 1.158 \pm 0.164,\frac{{\alpha _s^{uds} }}{{\alpha _s^{cb} }} = 1.038 \pm 0.221, \hfill \\ \end{gathered}$$ with quadratically combined statistical and systematic errors. We also compare the αs values for quarks of diffrent weak isospin, charge and generation. No evidence for a dependence of αs on any of these quark properties is observed. Finally, combining all samples and determining the α s f /α s incl ratio for each flavour, we do not find any dependence of the strong coupling constant on flavour.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesActon, P. D. ; Akers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Bartoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P.
Springer
Published 1993Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract The fractional partial width of theZ 0 tob quarks, $$\Gamma _{b\bar b} /\Gamma _{had} $$ , has been measured by OPAL using an impact parameter technique. The method has been developed using 130 000 hadronic events collected by OPAL in 1990. We find: $$\frac{{\Gamma _{b\bar b} }}{{\Gamma _{had} }} = 0.222 \pm 0.007(stat) \pm 0.008(sys).$$ The measurement assumes the relative rates of theZ 0 touds andc quarks given by the Standard Model. Varying the charm fraction from the Standard Model value of $$\Gamma _{c\bar c} /\Gamma _{had} = 0.171$$ changes the result by an additional $$\Delta \Gamma _{b\bar b} /\Gamma _{b\bar b} = - 0.135 \times \Delta \Gamma _{c\bar c} /\Gamma _{c\bar c} $$ .Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesAkers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Bartoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P.
Springer
Published 1994Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract We present measurements of the hadronic photon structure functionF 2 γ (x), in twoQ 2 ranges with mean values of 5.9 GeV2 and 14.7 GeV2. The data were taken by the OPAL experiment at LEP, with $$\sqrt s$$ close to theZ 0 mass and correspond to an integratede + e − luminosity of 44.8 pb−1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon hasQ 2〉4 GeV2. Our measurements extend to lower values ofx than any previous experiment, and no increase ofF 2 γ (x) is observed.Type of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesAkers, R. ; Alexander, G. ; Allison, J. ; Anderson, K. J. ; Arcelli, S. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barlow, R. J. ; Barnett, S. ; Bartoldus, R. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Beck, G. A. ; Becker, J. ; Beeston, C. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bentkowski, P. ; Berlich, P.
Springer
Published 1994Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract Using the distance from the average primary vertex to reconstructed secondary vertices in jets, samples of events withb purity varying from about 13% to 89% have been selected. The charged particle multiplicity in the hemispheres opposite those containing these jets has been studied as a function of theb purity of the events. Extrapolating to 0% and 100%b purity, values of the hemisphere charged particle multiplicity inZ 0→ $$b\bar b$$ events and in non- $$b\bar b$$ events have been measured to be $$\begin{gathered} \bar n_b = 11.71 \pm 0.03 \pm 0.18 \pm 0.21, \hfill \\ \bar n_{udsc} = 10.32 \pm 0.01 \pm 0.07 \pm 0.19. \hfill \\ \end{gathered}$$ The first error is statistical, the second systematic and the third is a common systematic error. The difference in charged particle multiplicity betweenb quark events and light (u, d, s) quark events has been measured and found to be $$\delta _{bl} = 3.02 \pm 0.05 \pm 0.79.$$ The result is compared to the predictions of MLLA QCD calculations. By studying the impact parameter distributions of charged particles in the hemispheres opposite these jets, the charged particle decay multiplicity ofB hadrons fromZ 0 decay, including particles fromK s 0 and Λ decay, has been measured to be $$\bar n^B = 5.51 \pm 0.05 \pm 0.51.$$ From the mean momentum of these decay products and separately from the number of primary charged particles perb event, the averagex E ofb flavoured hadrons has been measured to be $$\left\langle {x_E } \right\rangle _b = 0.693 \pm 0.003 \pm 0.030.$$Type of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesAlexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Armitage, J. C. ; Ashton, P. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bethke, S. ; Biebel, O.
Springer
Published 1991Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract We report on an improved measurement of the mass of theZ 0 boson, its total width and its partial decay widths into hadrons and leptons, as well as the effective axial vector and vector couplings to charged leptons. These measurements are based on a data set of approximately 160 000 hadronicZ 0 decays and 18 000 decays into electrons, muons and taus, recorded by the OPAL experiment at centre of mass energies near the mass of theZ 0. The total width and the partial widths to visible final states, derived from the measured cross sections, are used to extract the invisible width. The effective couplings of theZ 0 to charged leptons are studied using measurements of the lepton pair cross sections and forward-backward asymmetries at the different centre of mass energy points of theZ 0 scan. The implications of our results in the context of the Standard Model are discussed.Type of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesAkrawy, M. Z. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Armitage, J. C. ; Arnison, G. T. J. ; Ashton, P. ; Azuelos, G. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Bethke, S. ; Biebel, O. ; Binder, U. ; Bloodworth, I. J. ; Bock, P. ; Breuker, H.
Springer
Published 1991Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract A search for minimal standard model (MSM) and minimal supersymmetric model (MSSM), Higgs bosons with masses larger than 3 GeV/c2 has been performed by the OPAL collaboration one + e − data from LEP corresponding to an integrated luminosity of 1.24 pb−1. The limits for MSM Higgs bosons have been obtained using the channelsZ 0→Z 0* H 0,Z 0*→(v $$\bar v$$ ore + e − or µ+, µ−. The search for MSSM Higgs bosons has been performed using the channelsZ 0→Z 0* H 0,v $$\bar v$$ ore + e − or µ+µ−),h 0 →q $$\bar q$$ andZ 0→h 0 A 0,h 0 A 0→(4 jet orτ + τ −→ or 4τ), whereh 0 andA 0 are the two lightest neutral MSSM Higgs bosons. No Higgs boson signal has been observed. The MSM Higgs boson is excluded in the mass range 3 GeV 〈 $$m_{H^0 }$$ 〈25.3 GeV/c2 at the 95% confidence level; limits on the masses of the two lightest neutral MSSM Higgs bosons are obtained forh 0 mases up to 40.5 GeV/c2.Type of Medium: Electronic ResourceURL: -
20Articles: DFG German National LicensesActon, P. D. ; Alexander, G. ; Allison, J. ; Allport, P. P. ; Anderson, K. J. ; Arcelli, S. ; Ashton, P. ; Astbury, A. ; Axen, D. ; Azuelos, G. ; Bahan, G. A. ; Baines, J. T. M. ; Ball, A. H. ; Banks, J. ; Barker, G. J. ; Barlow, R. J. ; Batley, J. R. ; Beaudoin, G. ; Beck, A. ; Becker, J. ; Behnke, T. ; Bell, K. W. ; Bella, G. ; Berlich, P. ; Bethke, S.
Springer
Published 1992Staff ViewISSN: 1434-6052Source: Springer Online Journal Archives 1860-2000Topics: PhysicsNotes: Abstract The properties of final state photons in multihadronic decays of theZ 0 and those of the recoiling hadronic system are discussed and compared with theoretical expectations. The yield of two and three jet events with final state photons is found to be in good agreement with the expectation from a matrix element calculation ofO(αα s. Uncertainties in the interpretation of the theoretical calculation do not yet permit a final assessment of events with just one reconstructed jet. Comparing the rates of two jet events with a photon to those of three jet events in the inclusive multihadronic sample, the strong coupling constant in second order is determined asα s $$(M_{Z^0 } )$$ =0.122±0.010, taking into account only the statistical and experimental systematic errors. It is found that an abelian model of the strong interaction does not describe the data. The comparison of the total yield and the jet rates with QCD shower programs shows better agreement with the ARIADNE model than with the JETSET model. Both programs are found to describe well the photon properties and the properties of the residual hadronic event.Type of Medium: Electronic ResourceURL: