The process e + e − → γγ ( γ ) is studied using data recorded with the OPAL detector at LEP. The data sample corresponds to a total integrated luminosity of 56.2 pb − 1 taken at a centre-of-mass energy of 183 GeV. The measured cross-section agrees well with the expectation from QED. A fit to the angular distribution is used to obtain improved limits at 95% CL on the QED cut-off parameters: Λ + > 233 GeV and Λ − > 265 GeV as well as a mass limit for an excited electron, M e ∗ > 227 GeV assuming equal e ∗ e γ and ee γ couplings. No evidence for resonance production is found in the invariant mass spectrum of photon pairs. Limits are obtained for the cross-section times branching ratio for a resonance decaying into two photons.

Cross-sections and angular distributions for hadronic and lepton pair final states in e+e− collisions at a centre-of-mass energy near 189 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The results are used to measure the energy dependence of the electromagnetic coupling constant αem, and to place limits on new physics as described by four-fermion contact interactions or by the exchange of a new heavy particle such as a sneutrino in supersymmetric theories with R-parity violation. A search for the indirect effects of the gravitational interaction in extra dimensions on the μ+μ− and τ+τ− final states is also presented. Submitted to European Journal of Physics C The OPAL Collaboration G.Abbiendi, K.Ackerstaff, G.Alexander, J. Allison, K.J.Anderson, S.Anderson, S.Arcelli, S.Asai, S.F.Ashby, D.Axen, G.Azuelos, A.H.Ball, E. Barberio, R.J. Barlow, J.R.Batley, S. Baumann, J. Bechtluft, T.Behnke, K.W.Bell, G.Bella, A.Bellerive, S. Bentvelsen, S. Bethke, S. Betts, O.Biebel, A.Biguzzi, I.J. Bloodworth, P. Bock, J. Böhme, O.Boeriu, D.Bonacorsi, M.Boutemeur, S. Braibant, P. Bright-Thomas, L. Brigliadori, R.M.Brown, H.J. Burckhart, P.Capiluppi, R.K.Carnegie, A.A.Carter, J.R.Carter, C.Y.Chang, D.G.Charlton, D.Chrisman, C.Ciocca, P.E.L.Clarke, E.Clay, I. Cohen, J.E.Conboy, O.C.Cooke, J. Couchman, C.Couyoumtzelis, R.L.Coxe, M.Cuffiani, S.Dado, G.M.Dallavalle, S.Dallison, R.Davis, S.De Jong, A. de Roeck, P.Dervan, K.Desch, B.Dienes, M.S.Dixit, M.Donkers, J.Dubbert, E.Duchovni, G.Duckeck, I.P.Duerdoth, P.G.Estabrooks, E. Etzion, F. Fabbri, A. Fanfani, M. Fanti, A.A. Faust, L. Feld, P. Ferrari, F. Fiedler, M. Fierro, I. Fleck, A. Frey, A. Fürtjes, D.I. Futyan, P.Gagnon, J.W.Gary, G.Gaycken, C.Geich-Gimbel, G.Giacomelli, P.Giacomelli, W.R.Gibson, D.M.Gingrich, D.Glenzinski, J.Goldberg, W.Gorn, C.Grandi, K.Graham, E.Gross, J.Grunhaus, M.Gruwé, C.Hajdu G.G.Hanson, M.Hansroul, M.Hapke, K.Harder, A.Harel, C.K.Hargrove, M.Harin-Dirac, M.Hauschild, C.M.Hawkes, R.Hawkings, R.J.Hemingway, G.Herten, R.D.Heuer, M.D.Hildreth, J.C.Hill, P.R.Hobson, A.Hocker, K.Hoffman, R.J.Homer, A.K.Honma, D.Horváth, K.R.Hossain, R.Howard, P.Hüntemeyer, P. Igo-Kemenes, D.C. Imrie, K. Ishii, F.R. Jacob, A. Jawahery, H. Jeremie, M. Jimack, C.R. Jones, P. Jovanovic, T.R. Junk, N.Kanaya, J.Kanzaki, D.Karlen, V.Kartvelishvili, K.Kawagoe, T.Kawamoto, P.I.Kayal, R.K.Keeler, R.G.Kellogg, B.W.Kennedy, D.H.Kim, A.Klier, T.Kobayashi, M.Kobel, T.P.Kokott, M.Kolrep, S.Komamiya, R.V.Kowalewski, T.Kress, P.Krieger, J. von Krogh, T.Kuhl, P.Kyberd, G.D. Lafferty, H. Landsman, D. Lanske, J. Lauber, I. Lawson, J.G. Layter, D. Lellouch, J. Letts, L. Levinson, R. Liebisch, J. Lillich, B. List, C. Littlewood, A.W.Lloyd, S.L. Lloyd, F.K. Loebinger, G.D. Long, M.J. Losty, J. Lu, J. Ludwig, D. Liu, A.Macchiolo, A.Macpherson, W.Mader, M.Mannelli, S.Marcellini, T.E.Marchant, A.J.Martin, J.P.Martin, G.Martinez, T.Mashimo, P.Mättig, W.J.McDonald, J.McKenna, E.A.Mckigney , T.J.McMahon, R.A.McPherson, F.Meijers, P.Mendez-Lorenzo, F.S.Merritt, H.Mes, I.Meyer, A.Michelini, S.Mihara, G.Mikenberg, D.J.Miller, W.Mohr, A.Montanari, T.Mori, K.Nagai, I. Nakamura, H.A.Neal, R.Nisius, S.W.O’Neale, F.G.Oakham, F.Odorici, H.O.Ogren, A.Okpara, M.J.Oreglia, S.Orito, G. Pásztor, J.R. Pater, G.N.Patrick, J. Patt, R. Perez-Ochoa, S. Petzold, P. Pfeifenschneider , J.E. Pilcher, J. Pinfold, D.E. Plane, P. Poffenberger, B. Poli, J. Polok, M.Przybycień, A.Quadt, C.Rembser, H.Rick, S. Robertson, S.A.Robins, N.Rodning, J.M.Roney, S. Rosati, K.Roscoe, A.M.Rossi, Y.Rozen, K.Runge, O.Runolfsson, D.R.Rust, K. Sachs, T. Saeki, O. Sahr, W.M. Sang, E.K.G. Sarkisyan, C. Sbarra, A.D. Schaile, O. Schaile, P. Scharff-Hansen, J. Schieck, S. Schmitt, A. Schöning, M. Schröder, M. Schumacher, C. Schwick, W.G. Scott, R. Seuster, T.G. Shears, B.C. Shen, C.H. Shepherd-Themistocleous , P. Sherwood, G.P. Siroli, A. Skuja, A.M. Smith, G.A. Snow, R. Sobie, S. Söldner-Rembold , S. Spagnolo, M. Sproston, A. Stahl, K. Stephens, K. Stoll, D. Strom, R. Ströhmer, B. Surrow, S.D.Talbot, P.Taras,

The exclusive production of proton-antiproton pairs in the collisions of two quasi-real photons has been studied using data taken at √ see = 183GeV and 189GeV with the OPAL detector at LEP. Results are presented for pp̄ invariant masses, W , in the range 2.15 < W < 3.95GeV. The cross-section measurements are compared with previous data and with recent analytic calculations based on the quark-diquark model. (To be submitted to Eur. Phys. J. C.) The OPAL Collaboration G.Abbiendi, C.Ainsley, P.F. Åkesson, G.Alexander, J. Allison, P.Amaral, G.Anagnostou, K.J.Anderson, S.Arcelli, S.Asai, D.Axen, G.Azuelos, I. Bailey, E. Barberio, T.Barillari, R.J. Barlow, R.J. Batley, P. Bechtle, T.Behnke, K.W.Bell, P.J. Bell, G.Bella, A.Bellerive, G.Benelli, S. Bethke, O.Biebel, I.J. Bloodworth, O.Boeriu, P. Bock, D.Bonacorsi, M.Boutemeur, S. Braibant, L. Brigliadori, R.M.Brown, K.Buesser, H.J. Burckhart, S. Campana, R.K.Carnegie, B.Caron, A.A.Carter, J.R.Carter, C.Y.Chang, D.G.Charlton, A.Csilling , M.Cuffiani, S.Dado, G.M.Dallavalle, S.Dallison, A.De Roeck, E.A.De Wolf, K.Desch, B.Dienes, M.Donkers, J.Dubbert, E.Duchovni, G.Duckeck, I.P.Duerdoth, E. Elfgren, E. Etzion, F. Fabbri, L. Feld, P. Ferrari, F. Fiedler, I. Fleck, M. Ford, A. Frey, A. Fürtjes, P.Gagnon, J.W.Gary, G.Gaycken, C.Geich-Gimbel, G.Giacomelli, P.Giacomelli, M.Giunta, J.Goldberg, E.Gross, J.Grunhaus, M.Gruwé, P.O.Günther, A.Gupta, C.Hajdu, M.Hamann, G.G.Hanson, K.Harder, A.Harel, M.Harin-Dirac, M.Hauschild, J. Hauschildt, C.M.Hawkes, R.Hawkings, R.J.Hemingway, C.Hensel, G.Herten, R.D.Heuer, J.C.Hill, K.Hoffman, R.J.Homer, D.Horváth, R.Howard, P.Hüntemeyer, P. Igo-Kemenes, K. Ishii, H. Jeremie, P. Jovanovic, T.R. Junk, N.Kanaya, J.Kanzaki, G.Karapetian, D.Karlen, V.Kartvelishvili, K.Kawagoe, T.Kawamoto, R.K.Keeler, R.G.Kellogg, B.W.Kennedy, D.H.Kim, K.Klein, A.Klier, S.Kluth, T.Kobayashi, M.Kobel, S.Komamiya, L.Kormos, R.V.Kowalewski, T.Krämer, T.Kress, P.Krieger, J. von Krogh, D.Krop, K.Kruger, M.Kupper, G.D. Lafferty, H. Landsman, D. Lanske, J.G. Layter, A. Leins, D. Lellouch, J. Letts, L. Levinson, J. Lillich, S.L. Lloyd, F.K. Loebinger, J. Lu, J. Ludwig, A.Macpherson, W.Mader, S.Marcellini, T.E.Marchant, A.J.Martin, J.P.Martin, G.Masetti, T.Mashimo, P.Mättig, W.J.McDonald, J.McKenna, T.J.McMahon, R.A.McPherson, F.Meijers, P.Mendez-Lorenzo, W.Menges, F.S.Merritt, H.Mes, A.Michelini, S.Mihara, G.Mikenberg, D.J.Miller, S.Moed, W.Mohr, T.Mori, A.Mutter, K.Nagai, I. Nakamura, H.A.Neal, R.Nisius, S.W.O’Neale, A.Oh, A.Okpara, M.J.Oreglia, S.Orito, C. Pahl, G. Pásztor, J.R. Pater, G.N.Patrick, J.E. Pilcher, J. Pinfold, D.E. Plane, B. Poli, J. Polok, O. Pooth, M.Przybycień, A.Quadt, K.Rabbertz, C.Rembser, P.Renkel, H.Rick, J.M.Roney, S. Rosati, Y.Rozen, K.Runge, K. Sachs, T. Saeki, O. Sahr, E.K.G. Sarkisyan , A.D. Schaile, O. Schaile, P. Scharff-Hansen, J. Schieck, T. Schoerner-Sadenius, M. Schröder, M. Schumacher, C. Schwick, W.G. Scott, R. Seuster , T.G. Shears, B.C. Shen, C.H. Shepherd-Themistocleous , P. Sherwood, G. Siroli, A. Skuja, A.M. Smith, R. Sobie, S. Söldner-Rembold, S. Spagnolo, F. Spano, A. Stahl, K. Stephens, D. Strom, R. Ströhmer, S. Tarem, M.Tasevsky , R.J. Taylor, R.Teuscher, M.A.Thomson, E.Torrence, D.Toya, P.Tran, T.Trefzger, A.Tricoli, I. Trigger, Z. Trócsányi, E.Tsur, M.F.Turner-Watson, I. Ueda, B.Ujvári, B.Vachon, C.F.Vollmer, P.Vannerem, M.Verzocchi, H.Voss, J. Vossebeld, D.Waller, C.P.Ward, D.R.Ward, P.M.Watkins, A.T.Watson, N.K.Watson, P.S.Wells, T.Wengler, N.Wermes, D.Wetterling G.W.Wilson, J.A.Wilson, G.Wolf, T.R.Wyatt, S.Yamashita, D. Zer-Zion, L. Zivkovic

We present measurements of triple gauge boson coupling parameters using data recorded by the OPAL detector at LEP2 at a centre-of-mass energy of 172 GeV. A total of 120 W-pair candidates has been selected in the qqqq, qq ℓν ℓ and ℓν ℓ ℓ ′ ν ℓ ′ decay channels, for an integrated luminosity of 10.4 pb − 1 . We use these data to determine several different anomalous coupling parameters using the measured cross-section and the distributions of kinematic variables. We measure α Bφ =0 . 35 +1 . 29 − 1 . 07 ± 0 . 38, α Wφ =0 . 00 +0 . 30 − 0 . 28 ± 0 . 11, α W =0 . 18 +0 . 49 − 0 . 47 ± 0 . 23, ∆ g z1 = − 0 . 03 +0 . 40 − 0 . 37 ± 0 . 14, ∆ κ ( HISZ ) γ =0 . 03 +0 . 55 − 0 . 51 ± 0 . 20, and ∆ κ =0 . 03 +0 . 49 − 0 . 46 ± 0 . 21. Combining the α Wφ result with our previous result obtained from the 161 GeV data sample we measure α Wφ = − 0 . 08 +0 . 28 − 0 . 25 ± 0 . 10. All of these measurements are consistent with the Standard Model.

A search is described to detect charged Higgs bosons via the process e + e − → H + H − , using data collected by the OPAL detector at center-of-mass energies of 130 − 172 GeV with a total integrated luminosity of 25 pb − 1 . The decay channels are assumed to be H + → qq ′ and H + → τ + ν τ . No evidence for charged Higgs boson production is observed. The lower limit for its mass is determined to be 52 GeV at 95% confidence level, independent of the H + → τ + ν τ branching ratio. dashes indicate masses which are kinematically forbidden or not simulated. Note that there is significant overlap between the various M H ± -dependent selections.

We report a study of forward-backward multiplicity correlations and a measurement of the dependence on charged multiplicity of the mean transverse momentum of charged hadrons, measured with respect to the thrust axis. The study was performed on a high statistics sample of Z 0 decays to multihadronic (cid:12)nal states collected by the OPAL Collaboration at LEP. The positive forward-backward multiplicity correlation observed in our inclusive sample can be understood in terms of a superposition of distinct event topologies characterized by a di(cid:11)erent amount of hard gluon radiation (2-, 3-and 4-jet events) and with di(cid:11)erent mean multiplicities. The residual positive correlation that we see in a clean 2-jet sample can be interpreted in terms of fragmentation properties of di(cid:11)erent quark (cid:13)avours and of the production and decay of resonances. We have compared the observed e(cid:11)ects with the predictions of QCD-based parton shower models. The data are well described by the Jetset 7.3 Monte Carlo, while Herwig 5.5 does not satisfactorily reproduce the measured correlations. Hard gluon radiation is also shown to be responsible for the observed increase of about 40% in the mean transverse momentum of produced charged hadrons in the multiplicity range from 10 to 30. The comparison with the results obtained in an analysis of a sample enriched in Z 0 ! bb events, shows that the presence of heavy (cid:13)avours does not contribute signi(cid:12)cantly to the observed e(cid:11)ect.

Photonic events with large missing energy have been observed in ee collisions at a centre-ofmass energy of 189 GeV 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 ee → νν + photon(s). No evidence is observed for new physics contributions to these final states. Upper limits on σ(ee → XY) · BR(X → Yγ) and σ(ee → XX) · BR(X → Yγ) are derived for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos (X = ν∗, Y = ν), to neutralino production (X = χ̃02, Y = χ̃ 0 1) and to supersymmetric models in which X = χ̃01 and Y = G̃ is a light gravitino. The case of macroscopic decay lengths of particle X is considered for ee → XX, X → Yγ, when MY ≈ 0. The singlephoton 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. Submitted to Eur. Phys. J. C The OPAL Collaboration G. Abbiendi2, K.Ackerstaff8, C.Ainsley5, P.F. Akesson3, G.Alexander22, J.Allison16, K.J.Anderson9, S.Arcelli17, S.Asai23, S.F.Ashby1, D. Axen27, G. Azuelos18,a, I. Bailey26, A.H. Ball8, E.Barberio8, R.J. Barlow16, J.R. Batley5, S. Baumann3, T.Behnke25, K.W. Bell20, G. Bella22, A. Bellerive9, S. Bentvelsen8, S. Bethke14,i, O.Biebel14,i, I.J. Bloodworth1, P. Bock11, J. Böhme14,h, O.Boeriu10, D. Bonacorsi2, M. Boutemeur31, S. Braibant8, P.Bright-Thomas1, L. Brigliadori2, R.M. Brown20, H.J. Burckhart8, J. Cammin3, P.Capiluppi2, R.K. Carnegie6, A.A. Carter13, J.R.Carter5, C.Y. Chang17, D.G. Charlton1,b, C.Ciocca2, P.E.L. Clarke15, E.Clay15, I. Cohen22, O.C.Cooke8, J. Couchman15, C.Couyoumtzelis13, R.L.Coxe9, M. Cuffiani2, S.Dado21, G.M. Dallavalle2 , S.Dallison16, R. Davis28, A. de Roeck8, P. Dervan15, K.Desch25, B. Dienes30,h, M.S.Dixit7, M.Donkers6, J.Dubbert31, E. Duchovni24, G. Duckeck31, I.P. Duerdoth16, P.G. Estabrooks6, E. Etzion22, F. Fabbri2, M. Fanti2, A.A. Faust28, L. Feld10, P. Ferrari12, F. Fiedler8, I. Fleck10, M.Ford5, A. Frey8, A. Fürtjes8, D.I. Futyan16, P. Gagnon12, J.W. Gary4, G. Gaycken25, C.Geich-Gimbel3, G. Giacomelli2, P.Giacomelli8 , D.M. Gingrich28,a, D. Glenzinski9, J. Goldberg21, C.Grandi2, K.Graham26, E. Gross24, J.Grunhaus22, M. Gruwé25, P.O.Günther3, C.Hajdu29 G.G. Hanson12, M. Hansroul8, M. Hapke13, K.Harder25, A. Harel21, C.K.Hargrove7, M. Harin-Dirac4, A. Hauke3, M. Hauschild8, C.M. Hawkes1, R.Hawkings25, R.J. Hemingway6, C.Hensel25, G. Herten10, R.D. Heuer25, M.D. Hildreth8, J.C.Hill5, P.R. Hobson25, A.Hocker9, K.Hoffman8, R.J. Homer1, A.K.Honma8, D. Horváth29,c, K.R.Hossain28, R.Howard27, P. Hüntemeyer25, P. Igo-Kemenes11, D.C. Imrie25, K. Ishii23, F.R. Jacob20, A. Jawahery17, H. Jeremie18, C.R. Jones5, P. Jovanovic1, T.R. Junk6, N.Kanaya23, J.Kanzaki23, G. Karapetian18, D. Karlen6, V. Kartvelishvili16, K.Kawagoe23, T.Kawamoto23, P.I. Kayal28, R.K. Keeler26, R.G. Kellogg17, B.W. Kennedy20, D.H. Kim19, K.Klein11, A. Klier24, T. Kobayashi23, M. Kobel3, T.P. Kokott3, S.Komamiya23, R.V. Kowalewski26, T.Kress4, P. Krieger6, J. von Krogh11, T.Kuhl3, M. Kupper24, P. Kyberd13, G.D. Lafferty16, H. Landsman21, D. Lanske14, I. Lawson26, J.G. Layter4, A. Leins31, D. Lellouch24, J. Letts12, L. Levinson24, R. Liebisch11, J. Lillich10, B. List8, C. Littlewood5, A.W. Lloyd1, S.L. Lloyd13, F.K. Loebinger16, G.D. Long26, M.J. Losty7, J. Lu27, J. Ludwig10, A.Macchiolo18 , A.Macpherson28, W.Mader3, M.Mannelli8, S.Marcellini2, T.E.Marchant16, A.J. Martin13, J.P. Martin18, G. Martinez17, T.Mashimo23, P.Mättig24, W.J. McDonald28, J.McKenna27, T.J.McMahon1, R.A. McPherson26, F. Meijers8, P.Mendez-Lorenzo31, F.S. Merritt9, H.Mes7, A.Michelini2, S.Mihara23, G. Mikenberg24, D.J. Miller15, W. Mohr10, A. Montanari2, T.Mori23, K.Nagai8, I. Nakamura23, H.A. Neal12,f , R. Nisius8, S.W.O’Neale1, F.G. Oakham7, F. Odorici2, H.O.Ogren12, A. Oh8, A.Okpara11, M.J. Oreglia9, S.Orito23, G. Pásztor8,j , J.R.Pater16, G.N. Patrick20, J. Patt10, P. Pfeifenschneider14, J.E. Pilcher9, J. Pinfold28, D.E. Plane8, B. Poli2, J. Polok8, O.Pooth8, M.Przybycień8,d, A.Quadt8, C.Rembser8, H.Rick4, S.A. Robins21, N. Rodning28, J.M. Roney26, S.Rosati3, K.Roscoe16, A.M. Rossi2, Y. Rozen21, K.Runge10, O.Runolfsson8, D.R. Rust12, K. Sachs6, T. Saeki23, O. Sahr31, W.M. Sang25, E.K.G. Sarkisyan22, C. Sbarra26, A.D. Schaile31, O. Schaile31, P. Scharff-Hansen8, S. Schmitt11, M. Schröder8, M. Schumacher25, C. Schwick8, W.G. Scott20, R. Seuster14,h, T.G. Shears8, B.C. Shen4, C.H. Shepherd-Themistocleous5, P. Sherwood15, G.P. Siroli2, A. Skuja17, A.M. Smith8, G.A. Snow17, R. Sobie26, S. Söldner-Rembold10,e, S. Spagnolo20, M. Sproston20, A. Stahl3, K. Stephens16, K. Stoll10, D. Strom19, R. Ströhmer31, B. Surrow8, S.D. Talbot1, S. Tarem21, R.J.Taylor15, R.Teuscher9, M. Thiergen10, J. Thomas15, M.A. Thomson8, E.Torrence9, S. Towers6, T.Trefzger31, I. Trigger8, Z.Trócsányi30,g , E.Tsur22, M.F. Turner-Watson1, I. Ueda23, P. Vannerem10, M. Verzocchi8, H. Voss8, J. Vossebeld8, D. Waller6, C.P.Ward5, D.R. Ward5, P.M. Watkins1, A.T.Watson1, N.K.Watson1, P.S.Wells8, T.Wengler8, N.Wermes3, D. Wetterling11 J.S.White6, G.W. Wilson16, J.A.Wilson1, T.R.Wyatt16, S.Yamashita23, V. Zacek18, D. Zer-Zion8

The τ− → μ−ν̄μντ branching ratio has been measured using data collected from 1990 to 1995 by the OPAL detector at the LEP collider. The resulting value of B(τ− → μ−ν̄μντ ) = 0.1734 ± 0.0009(stat) ± 0.0006(syst) has been used in conjunction with other OPAL measurements to test lepton universality, yielding the coupling constant ratios gμ/ge = 1.0005± 0.0044 and gτ/ge = 1.0031± 0.0048, in good agreement with the Standard Model prediction of unity. A value for the Michel parameter η = 0.004 ± 0.037 has also been determined and used to find a limit for the mass of the charged Higgs boson, mH± > 1.28 tan β, in the Minimal Supersymmetric Standard Model. (To be submitted to Physics Letters B) The OPAL Collaboration G. Abbiendi2, C.Ainsley5, P.F. Åkesson3, G. Alexander22, J. Allison16, P.Amaral9, G. Anagnostou1, K.J.Anderson9, S.Arcelli2, S.Asai23, D. Axen27, G. Azuelos18,a, I. Bailey26, E.Barberio8,p, R.J. Barlow16, R.J. Batley5, P.Bechtle25 , T.Behnke25, K.W. Bell20, P.J. Bell1, G.Bella22, A. Bellerive6, G. Benelli4, S. Bethke32, O.Biebel31, I.J. Bloodworth1, O.Boeriu10, P.Bock11, D. Bonacorsi2, M. Boutemeur31, S. Braibant8, L. Brigliadori2, R.M. Brown20, K.Buesser25, H.J. Burckhart8, S. Campana4, R.K.Carnegie6, B. Caron28, A.A. Carter13, J.R.Carter5, C.Y. Chang17, D.G. Charlton1,b, A.Csilling8,g, M. Cuffiani2, S.Dado21, S.Dallison16, A.De Roeck8, E.A. De Wolf8,s, K.Desch25, B. Dienes30, M.Donkers6, J.Dubbert31, E.Duchovni24, G.Duckeck31 , I.P. Duerdoth16, E. Elfgren18, E. Etzion22, F. Fabbri2, L. Feld10, P. Ferrari8, F. Fiedler31, I. Fleck10, M. Ford5, A. Frey8, A. Fürtjes8, P.Gagnon12, J.W. Gary4, G. Gaycken25, C.Geich-Gimbel3, G. Giacomelli2, P.Giacomelli2 , M. Giunta4, J.Goldberg21, E. Gross24, J.Grunhaus22, M.Gruwé8, P.O. Günther3, A.Gupta9, C.Hajdu29, M. Hamann25, G.G. Hanson4, K.Harder25, A. Harel21, M. Harin-Dirac4, M. Hauschild8, J.Hauschildt25, C.M.Hawkes1, R.Hawkings8, R.J. Hemingway6, C.Hensel25, G. Herten10, R.D. Heuer25, J.C.Hill5, K.Hoffman9, R.J. Homer1, D. Horváth29,c, R. Howard27, P. Igo-Kemenes11, K. Ishii23, H. Jeremie18, P. Jovanovic1, T.R. Junk6, N. Kanaya26, J.Kanzaki23, G.Karapetian18, D. Karlen6, V.Kartvelishvili16, K.Kawagoe23, T.Kawamoto23, R.K.Keeler26, R.G. Kellogg17, B.W. Kennedy20, D.H. Kim19, K.Klein11,t, A. Klier24, S.Kluth32, T.Kobayashi23, M. Kobel3, S.Komamiya23, L.Kormos26, T.Krämer25, T.Kress4, P.Krieger6,l, J. von Krogh11, D. Krop12, K.Kruger8, T.Kuhl25, M. Kupper24, G.D. Lafferty16, H. Landsman21, D. Lanske14, J.G. Layter4, A. Leins31, D. Lellouch24, J. Letts, L. Levinson24, J. Lillich10, S.L. Lloyd13, F.K. Loebinger16, J. Lu27, J. Ludwig10, A.Macpherson28,i, W. Mader3, S.Marcellini2, T.E.Marchant16, A.J.Martin13, J.P. Martin18, G.Masetti2, T.Mashimo23, P. Mättig, W.J. McDonald28, J.McKenna27, T.J. McMahon1, R.A.McPherson26, F. Meijers8, P. Mendez-Lorenzo31, W. Menges25, F.S. Merritt9, H.Mes6,a, A. Michelini2, S.Mihara23, G. Mikenberg24, D.J. Miller15, S.Moed21, W.Mohr10, T.Mori23, A.Mutter10, K.Nagai13, I. Nakamura23, H.A. Neal33, R. Nisius32, S.W.O’Neale1, A. Oh8, A.Okpara11, M.J. Oreglia9, S.Orito23, C. Pahl32, G.Pásztor4,g, J.R.Pater16, G.N. Patrick20, J.E. Pilcher9, J. Pinfold28, D.E. Plane8, B. Poli2, J. Polok8, O.Pooth14, M. Przybycień8,n, A. Quadt3, K. Rabbertz8,r, C.Rembser8, P. Renkel24, H.Rick4, J.M. Roney26, S.Rosati3, Y. Rozen21, K. Runge10, K. Sachs6, T. Saeki23, O. Sahr31, E.K.G. Sarkisyan8,j , A.D. Schaile31, O. Schaile31, P. Scharff-Hansen8, J. Schieck32, T. Schörner-Sadenius8, M. Schröder8, M. Schumacher3, C. Schwick8, W.G. Scott20, R. Seuster14,f , T.G. Shears8,h, B.C. Shen4, P. Sherwood15, G. Siroli2, A. Skuja17, A.M. Smith8, R. Sobie26, S. Söldner-Rembold10,d, F. Spano9, A. Stahl3, K. Stephens16, D. Strom19, R. Ströhmer31, S. Tarem21, M.Tasevsky8, R.J.Taylor15, R.Teuscher9, M.A. Thomson5, E.Torrence19, D. Toya23, P. Tran4, T.Trefzger31, A. Tricoli2, I. Trigger8, Z.Trócsányi30,e, E.Tsur22, M.F. Turner-Watson1, I. Ueda23, B. Ujvári30,e, B. Vachon26, C.F. Vollmer31, P.Vannerem10, M. Verzocchi17, H. Voss8,q, J.Vossebeld8,h, D.Waller6, C.P. Ward5, D.R. Ward5, P.M. Watkins1, A.T.Watson1, N.K.Watson1, P.S.Wells8, T.Wengler8, N. Wermes3, D. Wetterling11 G.W. Wilson16,k, J.A. Wilson1, G. Wolf24, T.R.Wyatt16, S.Yamashita23, D. Zer-Zion4, L. Zivkovic24 1School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK 2Dipartimento di Fisica dell’ Università di Bologna and INFN, I-40126 Bologna, Italy 3Physikalisches Institut, Universität Bonn, D-53115 Bonn, Germany 4Department of Physics, University of California, Riverside CA 92521, USA 5Cavendish Laboratory, Cambridge CB3 0HE, UK 6Ottawa-Carleton Institute for Physics, Department of Physics, Carleton University, Ottawa, Ontario K1S

The rates are measured per hadronic Z decay for gluon splitting to bb quark pairs, g bb , and of events containing two bb quark pairs, g4b, 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 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 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 g4b, namely g bb = (3.07 ± 0.53(stat) ± 0.97(syst)) × 10, g4b = (0.36 ± 0.17(stat) ± 0.27(syst)) × 10 . Submitted to Eur. Phys. J. C The OPAL Collaboration G. Abbiendi, K.Ackerstaff, C.Ainsley, P.F. Akesson, G.Alexander, J.Allison, K.J.Anderson, S.Arcelli, S.Asai, S.F.Ashby, D. Axen, G. Azuelos, I. Bailey, A.H. Ball, E. Barberio, R.J. Barlow, S. Baumann, T.Behnke, K.W. Bell, G.Bella, A. Bellerive, S. Bentvelsen, S. Bethke, O.Biebel, I.J. Bloodworth, P.Bock, J. Böhme, O.Boeriu, D. Bonacorsi, M. Boutemeur, S. Braibant, P. Bright-Thomas, L. Brigliadori, R.M. Brown, H.J. Burckhart, J. Cammin, P. Capiluppi, R.K.Carnegie, A.A. Carter, J.R.Carter, C.Y. Chang, D.G. Charlton, C.Ciocca, P.E.L.Clarke, E.Clay, I. Cohen, O.C.Cooke, J. Couchman, C.Couyoumtzelis, R.L. Coxe, M. Cuffiani, S.Dado, G.M. Dallavalle , S.Dallison, A. de Roeck, P.Dervan, K.Desch, B. Dienes, M.S.Dixit, M. Donkers, J.Dubbert, E.Duchovni, G. Duckeck, I.P. Duerdoth, P.G. Estabrooks, E. Etzion, F. Fabbri, M. Fanti, L. Feld, P. Ferrari, F. Fiedler, I. Fleck, M.Ford, A. Frey, A. Fürtjes, D.I. Futyan, P. Gagnon, J.W. Gary, G. Gaycken, C.Geich-Gimbel, G. Giacomelli, P. Giacomelli, D. Glenzinski, J.Goldberg, C. Grandi, K.Graham, E.Gross, J.Grunhaus, M.Gruwé, P.O.Günther, C.Hajdu, G.G. Hanson, M. Hansroul, M. Hapke, K.Harder, A.Harel, C.K.Hargrove, M. Harin-Dirac, A.Hauke, M. Hauschild, C.M. Hawkes, R.Hawkings, R.J.Hemingway, C.Hensel, G. Herten, R.D. Heuer, M.D. Hildreth, J.C.Hill, A. Hocker, K.Hoffman, R.J.Homer, A.K. Honma, D. Horváth, K.R.Hossain, R. Howard, P. Hüntemeyer, P. Igo-Kemenes, K. Ishii, F.R. Jacob, A. Jawahery, H. Jeremie, C.R. Jones, P. Jovanovic, T.R. Junk, N. Kanaya, J.Kanzaki, G.Karapetian, D. Karlen, V.Kartvelishvili, K.Kawagoe, T.Kawamoto, R.K.Keeler, R.G. Kellogg, B.W. Kennedy, D.H. Kim, K.Klein, A. Klier, T. Kobayashi, M. Kobel, T.P. Kokott, S.Komamiya, R.V. Kowalewski, T.Kress, P. Krieger, J. von Krogh, T.Kuhl, M. Kupper, P. Kyberd, G.D. Lafferty, H. Landsman, D. Lanske, I. Lawson, J.G. Layter, A. Leins, D. Lellouch, J. Letts, L. Levinson, R. Liebisch, J. Lillich, B. List, C. Littlewood, A.W. Lloyd, S.L. Lloyd, F.K. Loebinger, G.D. Long, M.J. Losty, J. Lu, J. Ludwig, A.Macchiolo , A.Macpherson, W.Mader, M.Mannelli, S.Marcellini, T.E.Marchant, A.J. Martin, J.P. Martin, G. Martinez, T.Mashimo, P.Mättig, W.J. McDonald, J.McKenna, T.J.McMahon, R.A. McPherson, F. Meijers, P.Mendez-Lorenzo, F.S. Merritt, H.Mes, A.Michelini, S.Mihara, G. Mikenberg, D.J. Miller, W. Mohr, A. Montanari, T.Mori, K.Nagai, I. Nakamura, H.A. Neal , R. Nisius, S.W.O’Neale, F.G. Oakham, F. Odorici, H.O.Ogren, A. Oh, A.Okpara, M.J. Oreglia, S.Orito, G. Pásztor , J.R.Pater, G.N. Patrick, J. Patt, P. Pfeifenschneider, J.E. Pilcher, J. Pinfold, D.E. Plane, B. Poli, J. Polok, O.Pooth, M.Przybycień, A.Quadt, C.Rembser, H.Rick, S.A. Robins, N. Rodning, J.M. Roney, S.Rosati, K.Roscoe, A.M. Rossi, Y. Rozen, K.Runge, O.Runolfsson, D.R. Rust, K. Sachs, T. Saeki, O. Sahr, E.K.G. Sarkisyan, C. Sbarra, A.D. Schaile, O. Schaile, P. Scharff-Hansen, S. Schmitt, M. Schröder, M. Schumacher, C. Schwick, W.G. Scott, R. Seuster, T.G. Shears, B.C. Shen, C.H. Shepherd-Themistocleous, P. Sherwood, G.P. Siroli, A. Skuja, A.M. Smith, G.A. Snow, R. Sobie, S. Söldner-Rembold, S. Spagnolo, M. Sproston, A. Stahl, K. Stephens, K. Stoll, D. Strom, R. Ströhmer, B. Surrow, S.D. Talbot, S. Tarem, R.J.Taylor, R.Teuscher, M. Thiergen, J. Thomas, M.A. Thomson, E. Torrence, S. Towers, T.Trefzger, I. Trigger, Z.Trócsányi, E.Tsur, M.F. Turner-Watson, I. Ueda, P.Vannerem, M. Verzocchi, H.Voss, J.Vossebeld, D. Waller, C.P.Ward, D.R. Ward, P.M. Watkins, A.T.Watson, N.K.Watson, P.S.Wells, T.Wengler, N.Wermes, D. Wetterling J.S.White, G.W. Wilson, J.A.Wilson, T.R.Wyatt, S.Yamashita, V. Zacek, D. Zer-Zion

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 〈xE〉 = 0.7193 ± 0.0016(stat) −0.0033(syst) . (Submitted to Eur. Phys. J. C) The OPAL Collaboration G. Abbiendi2, C.Ainsley5, P.F. Åkesson3, G.Alexander22, J.Allison16, P. Amaral9, G. Anagnostou1, K.J.Anderson9, S.Arcelli2, S.Asai23, D. Axen27, G. Azuelos18,a, I. Bailey26, E.Barberio8, R.J. Barlow16, R.J. Batley5, P.Bechtle25 , T.Behnke25, K.W. Bell20, P.J. Bell1, G.Bella22, A. Bellerive6, G. Benelli4, S.Bethke32, O.Biebel32, I.J. Bloodworth1, O.Boeriu10, P. Bock11, D. Bonacorsi2, M. Boutemeur31, S. Braibant8, L. Brigliadori2, R.M. Brown20, K.Buesser25, H.J. Burckhart8, J. Cammin3, S. Campana4, R.K.Carnegie6, B. Caron28, A.A. Carter13, J.R.Carter5, C.Y. Chang17, D.G. Charlton1,b, I. Cohen22, A.Csilling8,g, M.Cuffiani2, S.Dado21, G.M. Dallavalle2 , S.Dallison16, A. De Roeck8, E.A. De Wolf8, K.Desch25, M. Donkers6, J.Dubbert31, E.Duchovni24, G. Duckeck31, I.P.Duerdoth16, E. Elfgren18, E. Etzion22, F. Fabbri2, L. Feld10, P. Ferrari12, F. Fiedler31, I. Fleck10, M. Ford5, A. Frey8, A. Fürtjes8, P. Gagnon12, J.W. Gary4, G. Gaycken25, C.Geich-Gimbel3, G. Giacomelli2, P.Giacomelli2 , M. Giunta4, J.Goldberg21, E. Gross24, J.Grunhaus22, M. Gruwé8, P.O.Günther3, A. Gupta9, C.Hajdu29, M.Hamann25, G.G. Hanson4, K.Harder25, A.Harel21, M. Harin-Dirac4, M.Hauschild8, J.Hauschildt25, C.M. Hawkes1, R.Hawkings8, R.J.Hemingway6, C.Hensel25, G. Herten10, R.D. Heuer25, J.C.Hill5, K.Hoffman9, R.J.Homer1, D.Horváth29,c, R. Howard27, P.Hüntemeyer25, P. Igo-Kemenes11, K. Ishii23, H. Jeremie18, P. Jovanovic1, T.R. Junk6, N.Kanaya26, J.Kanzaki23, G. Karapetian18, D. Karlen6, V.Kartvelishvili16, K.Kawagoe23, T.Kawamoto23, R.K.Keeler26, R.G. Kellogg17, B.W. Kennedy20, D.H. Kim19, K.Klein11, A.Klier24, S.Kluth32, T. Kobayashi23, M. Kobel3, T.P.Kokott3, S.Komamiya23, L.Kormos26, R.V. Kowalewski26, T.Krämer25, T.Kress4, P.Krieger6,l, J. von Krogh11, D. Krop12, M. Kupper24, P. Kyberd13, G.D. Lafferty16, H. Landsman21, D. Lanske14, J.G. Layter4, A. Leins31, D. Lellouch24, J. Letts12, L. Levinson24, J. Lillich10, S.L. Lloyd13, F.K. Loebinger16, J. Lu27, J. Ludwig10, A. Macpherson28,i, W. Mader3, S.Marcellini2, T.E. Marchant16, A.J. Martin13, J.P.Martin18, G. Masetti2, T.Mashimo23, P.Mättig, W.J.McDonald28, J.McKenna27, T.J.McMahon1, R.A. McPherson26, F. Meijers8, P. Mendez-Lorenzo31, W. Menges25, F.S.Merritt9, H. Mes6,a, A.Michelini2, S.Mihara23, G. Mikenberg24, D.J. Miller15, S.Moed21, W. Mohr10, T.Mori23, A.Mutter10, K.Nagai13, I. Nakamura23, H.A. Neal33, R.Nisius8, S.W. O’Neale1, A.Oh8, A. Okpara11, M.J. Oreglia9, S.Orito23, C. Pahl32, G. Pásztor8,g, J.R. Pater16, G.N. Patrick20, J.E. Pilcher9, J. Pinfold28, D.E. Plane8, B. Poli2, J. Polok8, O. Pooth14, M.Przybycień8,j , A.Quadt3, K.Rabbertz8, C.Rembser8, P.Renkel24, H. Rick4, J.M. Roney26, S.Rosati3, Y.Rozen21, K.Runge10, D.R. Rust12, K. Sachs6, T. Saeki23, O. Sahr31, E.K.G. Sarkisyan8,j , A.D. Schaile31, O. Schaile31, P. Scharff-Hansen8, J. Schieck32, T. Schoerner-Sadenius8, M. Schröder8, M. Schumacher3, C. Schwick8, W.G. Scott20, R. Seuster14,f , T.G. Shears8,h, B.C. Shen4, C.H. Shepherd-Themistocleous5, P. Sherwood15, G. Siroli2, A. Skuja17, A.M. Smith8, R. Sobie26, S. Söldner-Rembold10,d, S. Spagnolo20, F. Spano9, A. Stahl3, K. Stephens16, D. Strom19, R. Ströhmer31, S. Tarem21, M. Tasevsky8, R.J.Taylor15, R.Teuscher9, M.A. Thomson5, E.Torrence19, D. Toya23, P. Tran4, T.Trefzger31, A. Tricoli2, I. Trigger8, Z.Trócsányi30,e, E.Tsur22, M.F. Turner-Watson1, I. Ueda23, B. Ujvári30,e, B. Vachon26, C.F. Vollmer31, P. Vannerem10, M.Verzocchi17, H.Voss8, J.Vossebeld8, D. Waller6, C.P. Ward5, D.R. Ward5, P.M. Watkins1, A.T.Watson1, N.K.Watson1, P.S.Wells8, T.Wengler8, N. Wermes3, D. Wetterling11 G.W. Wilson16,k, J.A. Wilson1, G.Wolf24, T.R.Wyatt16, S.Yamashita23, V. Zacek18, D. Zer-Zion4, L. Zivkovic24 1School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK 2Dipartimento di Fisica dell’ Università di Bologna and INFN, I-40126 Bologna, Italy

A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 182.1 pb−1 taken at a centre-of-mass energy of 189 GeV with the OPAL detector at LEP. No evidence for chargino or neutralino production is found. Upper limits on chargino and neutralino pair production (χ̃1 χ̃ − 1 , χ̃ 0 1χ̃ 0 2) cross-sections are obtained as a function of the chargino mass (mχ̃± 1 ), the lightest neutralino mass (mχ̃0 1 ) and the second lightest neutralino mass (mχ̃0 2 ). Within the Constrained Minimal Supersymmetric Standard Model framework, and for mχ̃± 1 −mχ̃0 1 ≥ 5 GeV, the 95% confidence level lower limits on mχ̃± 1 are 93.6 GeV for tan β = 1.5 and 94.1 GeV for tan β = 35. These limits are obtained assuming a universal scalar mass m0 ≥ 500 GeV. The corresponding limits for all m0 are 78.0 and 71.7 GeV. The 95% confidence level lower limits on the lightest neutralino mass, valid for any value of tan β are 32.8 GeV for m0 ≥ 500 GeV and 31.6 GeV for all m0. (Submitted to Phys. Lett. B) The OPAL Collaboration G. Abbiendi, K. Ackerstaff, G. Alexander, J. Allison, K.J. Anderson, S. Anderson, S. Arcelli, S. Asai, S.F. Ashby, D. Axen, G. Azuelos, A.H. Ball, E. Barberio, R.J. Barlow, J.R. Batley, S. Baumann, J. Bechtluft, T. Behnke, K.W. Bell, G. Bella, A. Bellerive, S. Bentvelsen, S. Bethke, S. Betts, O. Biebel, A. Biguzzi, I.J. Bloodworth, P. Bock, J. Böhme, O. Boeriu, D. Bonacorsi, M. Boutemeur, S. Braibant, P. Bright-Thomas, L. Brigliadori, R.M. Brown, H.J. Burckhart, P. Capiluppi, R.K. Carnegie, A.A. Carter, J.R. Carter, C.Y. Chang, D.G. Charlton, D. Chrisman, C. Ciocca, P.E.L. Clarke, E. Clay, I. Cohen, J.E. Conboy, O.C. Cooke, J. Couchman, C. Couyoumtzelis, R.L. Coxe, M. Cuffiani, S. Dado, G.M. Dallavalle, S. Dallison, R. Davis, S. De Jong, A. de Roeck, P. Dervan, K. Desch, B. Dienes, M.S. Dixit, M. Donkers, J. Dubbert, E. Duchovni, G. Duckeck, I.P. Duerdoth, P.G. Estabrooks, E. Etzion, F. Fabbri, A. Fanfani, M. Fanti, A.A. Faust, L. Feld, P. Ferrari, F. Fiedler, M. Fierro, I. Fleck, A. Frey, A. Fürtjes, D.I. Futyan, P. Gagnon, J.W. Gary, G. Gaycken, C. Geich-Gimbel, G. Giacomelli, P. Giacomelli, W.R. Gibson, D.M. Gingrich, D. Glenzinski, J. Goldberg, W. Gorn, C. Grandi, K. Graham, E. Gross, J. Grunhaus, M. Gruwé, C. Hajdu G.G. Hanson, M. Hansroul, M. Hapke, K. Harder, A. Harel, C.K. Hargrove, M. Harin-Dirac, M. Hauschild, C.M. Hawkes, R. Hawkings, R.J. Hemingway, G. Herten, R.D. Heuer, M.D. Hildreth, J.C. Hill, P.R. Hobson, A. Hocker, K. Hoffman, R.J. Homer, A.K. Honma, D. Horváth, K.R. Hossain, R. Howard, P. Hüntemeyer, P. Igo-Kemenes, D.C. Imrie, K. Ishii, F.R. Jacob, A. Jawahery, H. Jeremie, M. Jimack, C.R. Jones, P. Jovanovic, T.R. Junk, N. Kanaya, J. Kanzaki, D. Karlen, V. Kartvelishvili, K. Kawagoe, T. Kawamoto, P.I. Kayal, R.K. Keeler, R.G. Kellogg, B.W. Kennedy, D.H. Kim, A. Klier, T. Kobayashi, M. Kobel, T.P. Kokott, M. Kolrep, S. Komamiya, R.V. Kowalewski, T. Kress, P. Krieger, J. von Krogh, T. Kuhl, P. Kyberd, G.D. Lafferty, H. Landsman, D. Lanske, J. Lauber, I. Lawson, J.G. Layter, D. Lellouch, J. Letts, L. Levinson, R. Liebisch, J. Lillich, B. List, C. Littlewood, A.W. Lloyd, S.L. Lloyd, F.K. Loebinger, G.D. Long, M.J. Losty, J. Lu, J. Ludwig, D. Liu, A. Macchiolo, A. Macpherson, W. Mader, M. Mannelli, S. Marcellini, T.E. Marchant, A.J. Martin, J.P. Martin, G. Martinez, T. Mashimo, P. Mättig, W.J. McDonald, J. McKenna, E.A. Mckigney , T.J. McMahon, R.A. McPherson, F. Meijers, P. Mendez-Lorenzo, F.S. Merritt, H. Mes, I. Meyer, A. Michelini, S. Mihara, G. Mikenberg, D.J. Miller, W. Mohr, A. Montanari, T. Mori, K. Nagai, I. Nakamura, H.A. Neal , R. Nisius, S.W. O’Neale, F.G. Oakham, F. Odorici, H.O. Ogren, A. Okpara, M.J. Oreglia, S. Orito, G. Pásztor, J.R. Pater, G.N. Patrick, J. Patt, R. Perez-Ochoa, S. Petzold, P. Pfeifenschneider , J.E. Pilcher, J. Pinfold, D.E. Plane, P. Poffenberger, B. Poli, J. Polok, M. Przybycień, A. Quadt, C. Rembser, H. Rick, S. Robertson, S.A. Robins, N. Rodning, J.M. Roney, S. Rosati, K. Roscoe, A.M. Rossi, Y. Rozen, K. Runge, O. Runolfsson, D.R. Rust, K. Sachs, T. Saeki, O. Sahr, W.M. Sang, E.K.G. Sarkisyan, C. Sbarra, A.D. Schaile, O. Schaile, P. Scharff-Hansen, J. Schieck, S. Schmitt, A. Schöning, M. Schröder, M. Schumacher, C. Schwick, W.G. Scott, R. Seuster, T.G. Shears, B.C. Shen, C.H. Shepherd-Themistocleous , P. Sherwood, G.P. Siroli, A. Skuja, A.M. Smith, G.A. Snow, R. Sobie, S. Söldner-Rembold, S. Spagnolo, M. Sproston, A. Stahl, K. Stephens, K. Stoll, D. Strom, R. Ströhmer, B. Surrow, S.D. Talbot, P. Taras, S. Tarem, R. Teuscher, M. Thiergen, J. Thomas, M.A. Thomson, E. Torrence,

We report a measurement of the B 0s meson lifetime from B 0s → D − s X decays, where D − s mesons are reconstructed in the D − s → φπ − and D − s → K ∗ 0 K − decay channels. From approximately 3.7 million hadronic Z 0 decays recorded by the OPAL detector at LEP a sample is selected containing 911 ± 83 candidates, of which 519 ± 136 are estimated to be from B 0s meson decays. Fitting the distribution of the distance from the beam spot to the decay vertex of the D − s candidates with an unbinned likelihood function we measure where the errors are statistical and systematic, respectively.

From about 4 million hadronic Z 0 decays recorded by the OPAL detector on and near to the Z 0 resonance, we select a sample of more than 570 000 inclusively reconstructed B mesons. Orbitally-excited mesons B J are reconstructed using B combinations. Independently , B mesons are reconstructed using the decay B ! B. The selected B candidates are used to obtain samples enriched or depleted in the decay B J ! B (X), where (X) refers to decay modes with or without additional accompanying decay particles. From the number of signal candidates in the B mass spectra of these two samples, we perform the rst measurement of the branching ratio of orbitally-excited B mesons decaying into B (X): where the rst error is statistical and the second systematic. If B J decay modes other than single pion transitions can be neglected the measured ratio corresponds to the branching ratio BR(B J ! B). In the framework of Heavy Quark Symmetry, a simultaneous t to the B mass spectra of the samples enriched or depleted in B J ! B (X) decays yields the mass and the width of the B 1 (3=2) state, as well as the branching ratio of B J mesons decaying into B : where the uncertainties are statistical and systematic, respectively.

A search for stable and long-lived massive particles of electric charge |Q/e| = 1 or 2/3, pair-produced in ee collisions at centre-of-mass energies from 130 to 183 GeV, is reported by the OPAL collaboration at LEP. No evidence for production of these particles was observed in a mass range between 45 and 89.5 GeV. Model-independent upper limits on the production cross-section between 0.05 and 0.19 pb have been derived for scalar and spin-1/2 particles with charge ±1. Within the framework of the minimal supersymmetric model (MSSM), this implies a lower limit of 82.5 (83.5) GeV on the mass of long-lived right(left-)handed scalar muons and scalar taus. Long-lived charged leptons and charginos are excluded for masses below 89.5 GeV. For particles with charge ±2/3 the upper limits on the production cross-section vary between 0.05 and 0.2 pb. All limits, on masses and on cross-sections, are valid at the 95% confidence level for particles with lifetimes longer than 10 s. (Submitted to Physics Letters B) The OPAL Collaboration K.Ackerstaff, G.Alexander, J. Allison, N.Altekamp, K.J.Anderson, S.Anderson, S.Arcelli, S.Asai, S.F.Ashby, D.Axen, G.Azuelos, A.H.Ball, E. Barberio, R.J. Barlow, R.Bartoldus, J.R.Batley, S. Baumann, J. Bechtluft, T.Behnke, K.W.Bell, G.Bella, S. Bentvelsen, S. Bethke, S. Betts, O.Biebel, A.Biguzzi, S.D.Bird, V.Blobel, I.J. Bloodworth, M.Bobinski, P. Bock, D.Bonacorsi, M.Boutemeur, S. Braibant, L. Brigliadori, R.M.Brown, H.J. Burckhart, C.Burgard, R.Bürgin, P.Capiluppi, R.K.Carnegie, A.A.Carter, J.R.Carter, C.Y.Chang, D.G.Charlton, D.Chrisman, P.E.L.Clarke, I. Cohen, J.E.Conboy, O.C.Cooke, C.Couyoumtzelis , R.L.Coxe, M.Cuffiani, S.Dado, C.Dallapiccola, G.M.Dallavalle, R.Davis, S.De Jong, L.A. del Pozo, A. de Roeck, K.Desch, B.Dienes, M.S.Dixit, M.Doucet, E.Duchovni, G.Duckeck, I.P.Duerdoth, D. Eatough, P.G.Estabrooks, E. Etzion, H.G.Evans, M.Evans, F. Fabbri, A. Fanfani, M.Fanti, A.A. Faust, L. Feld, F. Fiedler, M.Fierro, H.M.Fischer, I. Fleck, R. Folman, D.G.Fong, M.Foucher, A. Fürtjes, D.I. Futyan, P.Gagnon, J.W.Gary, J.Gascon, S.M.Gascon-Shotkin, N.I.Geddes, C.Geich-Gimbel, T.Geralis, G.Giacomelli, P.Giacomelli, R.Giacomelli, V.Gibson, W.R.Gibson, D.M.Gingrich, D.Glenzinski, J.Goldberg, M.J.Goodrick, W.Gorn, C.Grandi, E.Gross, J.Grunhaus, M.Gruwé, C.Hajdu, G.G.Hanson, M.Hansroul, M.Hapke, C.K.Hargrove, P.A.Hart, C.Hartmann, M.Hauschild, C.M.Hawkes, R.Hawkings, R.J.Hemingway, M.Herndon, G.Herten, R.D.Heuer, M.D.Hildreth, J.C.Hill, S.J.Hillier, P.R.Hobson, A.Hocker, R.J.Homer, A.K.Honma, D.Horváth, K.R.Hossain, R.Howard, P.Hüntemeyer, D.E.Hutchcroft, P. Igo-Kemenes, D.C. Imrie, K. Ishii, A. Jawahery, P.W. Jeffreys, H. Jeremie, M. Jimack, A. Joly, C.R. Jones, M. Jones, U. Jost, P. Jovanovic, T.R. Junk, J.Kanzaki, D.Karlen, V.Kartvelishvili, K.Kawagoe, T.Kawamoto, P.I.Kayal, R.K.Keeler, R.G.Kellogg, B.W.Kennedy, J.Kirk, A.Klier, S.Kluth, T.Kobayashi, M.Kobel, D.S.Koetke, T.P.Kokott, M.Kolrep, S.Komamiya, R.V.Kowalewski, T.Kress, P.Krieger, J. von Krogh, P.Kyberd, G.D. Lafferty, R. Lahmann, W.P. Lai, D. Lanske, J. Lauber, S.R. Lautenschlager, I. Lawson, J.G. Layter, D. Lazic, A.M.Lee, E. Lefebvre, D. Lellouch, J. Letts, L. Levinson, B. List, S.L. Lloyd, F.K. Loebinger, G.D. Long, M.J. Losty, J. Ludwig, D. Lui, A.Macchiolo, A.Macpherson, M.Mannelli, S.Marcellini, C.Markopoulos, C.Markus, A.J.Martin, J.P.Martin, G.Martinez, T.Mashimo, P.Mättig, W.J.McDonald, J.McKenna, E.A.Mckigney, T.J.McMahon, R.A.McPherson, F.Meijers, S.Menke, F.S.Merritt, H.Mes, J.Meyer, A.Michelini, S.Mihara, G.Mikenberg, D.J.Miller, A.Mincer, R.Mir, W.Mohr, A.Montanari, T.Mori, K.Nagai, I. Nakamura, H.A.Neal, B.Nellen, R.Nisius, S.W.O’Neale, F.G.Oakham, F.Odorici, H.O.Ogren, A.Oh, N.J.Oldershaw, M.J.Oreglia, S.Orito, J. Pálinkás, G. Pásztor, J.R.Pater, G.N.Patrick, J. Patt, R. Perez-Ochoa, S. Petzold, P. Pfeifenschneider , J.E. Pilcher, J. Pinfold, D.E.Plane, P. Poffenberger, B. Poli, A. Posthaus, C.Rembser, S. Robertson, S.A.Robins, N.Rodning, J.M.Roney, A.Rooke, A.M.Rossi, P.Routenburg, Y.Rozen, K.Runge, O.Runolfsson, U.Ruppel, D.R.Rust, K. Sachs, T. Saeki, O. Sahr, W.M. Sang, E.K.G. Sarkisyan, C. Sbarra, A.D. Schaile, O. Schaile, F. Scharf, P. Scharff-Hansen, J. Schieck, P. Schleper, B. Schmitt, S. Schmitt, A. Schöning, M. Schröder, M. Schumacher, C. Schwick , W.G. Scott,

A study of W+W− events accompanied by hard photon radiation, Eγ > 2.5 GeV, produced in e+e− collisions at LEP is presented. Events consistent with being two on-shell W-bosons and an isolated photon are selected from 681 pb−1 of data recorded at 180 GeV < √ s < 209 GeV. From the sample of 187 selected W+W−γ candidates with photon energies greater than 2.5 GeV, the W+W−γ cross-section is determined at five values of √ s. The results are consistent with the Standard Model expectation. Averaging over all energies, the ratio of the observed cross-section to the Standard Model expectation is R(data/SM) = 0.99 ± 0.09 ± 0.04, where the errors represent the statistical and systematic uncertainties respectively. These data provide constraints on the related O(α) systematic uncertainties on the measurement of the W-boson mass at LEP. Finally, the data are used to derive 95 % confidence level upper limits on possible anomalous contributions to the W+W−γγ and W+W−Z0γ vertices: −0.020 GeV−2 < a0/Λ < 0.020 GeV−2, −0.053 GeV−2 < ac/Λ < 0.037 GeV−2, −0.16 GeV−2 < an/Λ < 0.15 GeV−2, where Λ represents the energy scale for new physics and a0, ac and an are dimensionless coupling constants. (To be Submitted to Physics Letters B) The OPAL Collaboration G. Abbiendi, C. Ainsley, P.F. Åkesson, G. Alexander, J. Allison, P. Amaral, G. Anagnostou, K.J. Anderson, S. Arcelli, S. Asai, D. Axen, G. Azuelos, I. Bailey, E. Barberio, R.J. Barlow, R.J. Batley, P. Bechtle, T. Behnke, K.W. Bell, P.J. Bell, G. Bella, A. Bellerive, G. Benelli, S. Bethke, O. Biebel, O. Boeriu, P. Bock, M. Boutemeur, S. Braibant, L. Brigliadori, R.M. Brown, K. Buesser, H.J. Burckhart, S. Campana, R.K. Carnegie, B. Caron, A.A. Carter, J.R. Carter, C.Y. Chang, D.G. Charlton, A. Csilling, M. Cuffiani, S. Dado, A. De Roeck, E.A. De Wolf, K. Desch, B. Dienes, M. Donkers, J. Dubbert, E. Duchovni, G. Duckeck, I.P. Duerdoth, E. Etzion, F. Fabbri, L. Feld, P. Ferrari, F. Fiedler, I. Fleck, M. Ford, A. Frey, A. Fürtjes, P. Gagnon, J.W. Gary, G. Gaycken, C. Geich-Gimbel, G. Giacomelli, P. Giacomelli, M. Giunta, J. Goldberg, E. Gross, J. Grunhaus, M. Gruwé, P.O. Günther, A. Gupta, C. Hajdu, M. Hamann, G.G. Hanson, K. Harder, A. Harel, M. Harin-Dirac, M. Hauschild, C.M. Hawkes, R. Hawkings, R.J. Hemingway, C. Hensel, G. Herten, R.D. Heuer, J.C. Hill, K. Hoffman, D. Horváth, P. Igo-Kemenes, K. Ishii, H. Jeremie, P. Jovanovic, T.R. Junk, N. Kanaya, J. Kanzaki, G. Karapetian, D. Karlen, K. Kawagoe, T. Kawamoto, R.K. Keeler, R.G. Kellogg, B.W. Kennedy, D.H. Kim, K. Klein, A. Klier, S. Kluth, T. Kobayashi, M. Kobel, S. Komamiya, L. Kormos, T. Krämer, P. Krieger, J. von Krogh, K. Kruger, T. Kuhl, M. Kupper, G.D. Lafferty, H. Landsman, D. Lanske, J.G. Layter, A. Leins, D. Lellouch, J. Letts, L. Levinson, J. Lillich, S.L. Lloyd, F.K. Loebinger, J. Lu, J. Ludwig, A. Macpherson, W. Mader, S. Marcellini, A.J. Martin, G. Masetti, T. Mashimo, P. Mättig, W.J. McDonald, J. McKenna, T.J. McMahon, R.A. McPherson, F. Meijers, W. Menges, F.S. Merritt, H. Mes, A. Michelini, S. Mihara, G. Mikenberg, D.J. Miller, S. Moed, W. Mohr, T. Mori, A. Mutter, K. Nagai, I. Nakamura , H. Nanjo, H.A. Neal, R. Nisius, S.W. O’Neale, A. Oh, A. Okpara, M.J. Oreglia, S. Orito23,∗, C. Pahl, G. Pásztor, J.R. Pater, G.N. Patrick, J.E. Pilcher, J. Pinfold, D.E. Plane, B. Poli, J. Polok, O. Pooth, M. Przybycień, A. Quadt, K. Rabbertz, C. Rembser, P. Renkel, J.M. Roney, S. Rosati, Y. Rozen, K. Runge, K. Sachs, T. Saeki, E.K.G. Sarkisyan , A.D. Schaile, O. Schaile, P. Scharff-Hansen, J. Schieck, T. Schörner-Sadenius, M. Schröder, M. Schumacher, C. Schwick , W.G. Scott, R. Seuster , T.G. Shears, B.C. Shen, P. Sherwood, G. Siroli, A. Skuja, A.M. Smith, R. Sobie, S. Söldner-Rembold, F. Spano, A. Stahl, K. Stephens, D. Strom, R. Ströhmer, S. Tarem, M. Tasevsky, R.J. Taylor, R. Teuscher, M.A. Thomson, E. Torrence, D. Toya, P. Tran, I. Trigger, Z. Trócsányi, E. Tsur, M.F. Turner-Watson, I. Ueda, B. Ujvári, C.F. Vollmer, P. Vannerem, R. Vértesi, M. Verzocchi, H. Voss , J. Vossebeld, D. Waller, C.P. Ward, D.R. Ward, P.M. Watkins, A.T. Watson, N.K. Watson, P.S. Wells, T. Wengler, N. Wermes, D. Wetterling G.W. Wilson, J.A. Wilson, G. Wolf, T.R. Wyatt, S. Yamashita, D. Zer-Zion, L. Zivkovic School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK Dipartimento di Fisica dell’ Università di Bologna and INFN, I-40126 Bologna, Italy Physikalisches Institut, Universität Bonn, D-53115 Bonn, Germany

The forward-backward asymmetry of e + e ? ! Z 0 ! bb has been measured using approximately 2.15 million hadronic Z 0 decays collected at the LEP e + e ? collider with the OPAL detector. A lifetime tag technique was used to select an enriched bb event sample. The measurement of the bb asymmetry was then performed using a jet charge algorithm to determine the direction of the primary quark. were measured where, in each case, the rst error is statistical, the second is systematic and the third term gives the variation due to a change (? bb =? had) in the value of ? bb =? had = 0:216 assumed. The dependence on the assumed charm asymmetry at the same energy is (A b FB) +0:077(A c FB). Assuming the Standard Model form for the couplings, these measurements correspond to an eeective weak mixing angle of: sin 2 ee;e +16 ?19 GeV/c 2 , where the rst error is statistical and the second is systematic. The Higgs mass assumed is 300 GeV/c 2. A variation in the assumed mass of the Higgs boson between 60 and 1000 GeV/c 2 corresponds to an uncertainty in sin 2 ee;e W of 0:00006 and on M top of +20 ?26 GeV/c 2 .

A study of b quark fragmentation at LEP is presented using a sample of semileptonic B decays containing a fully reconstructed charm meson. The data are compared to several theoretical models for heavy quark fragmentation; the free parameters in these models are tted and the sensitivity of the model parameters to the rate of P-wave B meson production is studied. The mean scaled energy fraction of B 0 and B + mesons has been determined to be hx E i = 0:695 0:006 0:003 0:007, where the errors are statistical, systematic and model dependence respectively. This result is consistent with previous, less direct measurements from inclusive leptonic B decays. Also presented is a model independent t to the shape of the energy distribution of weakly decaying B mesons at LEP.

We report a measurement of the branching ratio B(D + ! 0 ` + `)/ B(D + ! K 0 ` + `) from the Fermilab charm hadroproduction experiment E791. Based on signals of 49 17 events in the D + ! 0 e + e mode and 54 18 events in the D + ! 0 + mode, we measure Combining the results from both the electronic and muonic modes, we obtain 2 Semileptonic charm decays are useful in probing the dynamics of hadronic currents since the Cabibbo-Kobayashi-Maskawa matrix elements for the charm sector are well-known from unitarity constraints. Form factors for Cabibbo-suppressed (CS) c ! d semileptonic decays can be related via Heavy Quark EEective Theory (HQET) to those for b ! u semileptonic decays at the same four-velocity transfer 1]. Since knowledge of the form factors in b ! u transitions is vital for extracting V ub from b ! u semileptonic decays in a model-independent way, study of c ! d semileptonic decays can improve our knowledge of V ub. Although considerable progress has been made in studying CS semileptonic charm decays to pseudoscalar mesons 2], the only previous result on CS semileptonic charm decay to a vector meson is based on four D + ! 0 + events 3]. In this Letter, we report a new measurement from the Fermilab hadroproduction experiment E791 of B(D + ! 0 ` + `)=B(D + ! K 0 ` + `) based on more than 100 D + ! 0 ` + ` decays in the combined electronic and muonic modes. The E791 experiment 4] recorded 2 10 10 events from 500 GeV/c ? interactions in ve thin targets (one platinum, four diamond) separated by gaps of 1.34 to 1.39 cm. Precision tracking and vertexing information was provided by 23 silicon microstrip detectors (6 upstream and 17 downstream of the targets) and 35 drift chamber planes. Momentum was measured with two dipole magnets. Two segmented threshold Cerenkov counters provided =K separation in the 6 ? 60 GeV/c momentum range 5]. (charge-conjugate states are implied throughout this Letter) are selected by requiring a three-prong decay vertex of charge 1 with one of the decay particles being identiied as a lepton. A segmented lead and liquid-scintillator calorimeter 6] is used to identify the electrons, based on energy deposition and transverse shower shape. The probability that a (K) is misidentiied as …

A search for the Higgsstrahlung process e+e−→hZ is described, where the neutral Higgs boson h is assumed to decay into hadronic final states. In order to be sensitive to a broad range of models, the search is performed independent of the flavour content of the Higgs boson decay. The analysis is based on e+e− collision data collected by the OPAL detector at energies between 192 and 209 GeV. The search does not reveal any significant excess over the Standard Model background prediction. Results are combined with previous searches at energies around 91 and at 189 GeV. A limit is set on the product of the cross-section and the hadronic branching ratio of the Higgs boson, as a function of the Higgs boson mass. Assuming the hZ coupling predicted by the Standard Model, and a Higgs boson decaying only into hadronic final states, a lower bound of 104 GeV/c2 is set on the mass at the 95% confidence level.

Using the entire OPAL LEP1 on-peak Z hadronic decay sample, Z -> qbarq gamma decays were selected by tagging hadronic final states with isolated photon candidates in the electromagnetic calorimeter. Combining the measured rates of Z -> qbarq gamma decays with the total rate of hadronic Z decays permits the simultaneous determination of the widths of the Z into up- and down-type quarks. The values obtained, with total errors, were Gamma u = 300 ^{+19}_{-18} MeV and Gamma d = 381 ^{+12}_{-12} MeV. The results are in good agreement with the Standard Model expectation.