Showing papers by "D. M. Strom published in 1997"

QCD studies with e(+)e(-) annihilation data at 172-189 GeV

Abstract: We have studied hadronic events from $\mathrm{e^+e^-}$ 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 $\langle n_{\mathrm{ch}}\rangle$ 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 $ , $\langle n_{\mathrm{ch}}\rangle$ and $\xi_0$ are consistent with previous determinations at $\sqrt{s}=M_{\mathrm{Z^0}}$ .

A study of B meson oscillations using hadronic Z(0) decays containing leptons

Abstract: An event sample enriched in semileptonic decays of b hadrons is selected using an inclusive lepton selection from approximately 3.0 million hadronic Z(0) decays collected with the OPAL detector. This sample is used to investigate B meson oscillations by reconstructing a proper decay time for the parent of each lepton, using a jet charge method to estimate the production flavour of this parent, and using the lepton charge to tag the decay flavour. We measure the mass difference between the two B-d(0) mass eigenstates upper-delta-m(d)=0.444plusminus0.029(-0.017)(+0.020)ps(-1).For the B-s(0) system, we find upper-delta-m(s)>3.1ps(-1) at the 95% confidence level. This limit varies only a little if alternative limit setting approaches are adopted. Regions at higher upper-delta-m(s) values are also excluded with some methods for setting the limit.By studying the charge symmetry of the B-d(0) mixing structure, we are able to constrain possible CP and CPT violating effects. We measure the CP violation parameter Re-epsilon(B)=-0.006plusminus0.010plusminus0.006 and the indirect CPT violating parameter Im-delta(B)=-0.020plusminus0.016plusminus0.006. If we invoke CPT symmetry, then we obtain Re-epsilon(B)=0.002plusminus0.007plusminus0.003.

Strange baryon production in hadronic Z0 decays

Abstract: 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.

Study of phi (1020), D*+- and B* spin alignment in hadronic Z0 decays

Abstract: Measurements of helicity density matrix elements have been made for the φ(1020), D*± and B* vector mesons in multihadronic Z0 decays in the OPAL experiment at LEP. Results for inclusive φ produced with high energy show evidence for production preferentially in the helicity zero state, with ρ00 = 0.54 ± 0.08, compared to the value of 1/3 expected for no spin alignment. The corresponding element for the D*± has a value of 0.40 ± 0.02, also suggesting a deviation from 1/3. The B* result, with ρ00 = 0.36 ± 0.09, is consistent with no spin alignment. Off-diagonal elements have been measured for the f and D* mesons; for the D* the element Re ρ1−1 is non-zero, indicating non-independent fragmentation of the primary quarks.

Production of P-wave charm and charm-strange mesons in hadronic Z(0) decays

Abstract: Results are presented on the production of excited charm and excited charm-strange mesons in hadronic Z(0) decays. The results are obtained from approximately 4.3 million hadronic Z(0) decays, collected on or near the Z(0) resonance using the OPAL detector at LEP. The D-1(0)(2420) and D*(0)(2)(2460) mesons are reconstructed in the D*(+)pi(-) final state and their separate production rates in charm fragmentation and in weak decays of b-hadrons are determined. Assuming that the decay widths of these mesons are saturated by the allowed D*pi and D pi final states, the charm hadronization fractions and the inclusive branching ratios of b-hadrons to these neutral P-wave charm mesons are determined to bef(c --> D-1(0)) = 0.021 +/- 0.007(stat) +/- 0.003(syst), f(c --> D*(0)(2)) = 0.052 +/- 0.022(stat)+/- 0.013(syst), f(b --> D-1(0)) = 0.050 +/- 0.014(stat) +/- 0.006(syst), f(b --> D*(0)(2)) = 0.047 +/- 0.024(stat) +/- 0.013(syst).We also present the first observation at LEP of the D-s1(+)(2536) meson which is reconstructed in both the D*K-+(s)0 and D*K-0(+) final states After correcting for the expected contribution from bb events, assuming that the D*K channels saturate the available final states, these results are used to derive the charm hadronization fraction f(c --> D-s1(+)):f(c --> D-s1(+)) = 0.016 +/- 0.004(stat) +/- 0.003(syst).

Σ+, Σ0 and Σ− hyperon production in hadronic Z0 decays

Abstract: 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: ${1⩈er 3}[n_{Sigma^{+}+Sigma^{0}+Sigma^{-}}]=0.084pm 0.005 ({⤪ stat.}) pm 0.008 ({⤪ syst.})$.

Inclusive jet production in photon-photon collisions at root s(ee)=130 and 136 GeV

Abstract: The inclusive one- and two-jet production cross-sections are measured in collisions of quasi-real photons radiated from the LEP beams at e+e- centre-of-mass energies √see = 130 and 136 GeV using the OPAL detector at LEP. Hard jets are reconstructed using a cone jet finding algorithm. The differential jet cross-sections dσ/dETjet are compared to next-to-leading order perturbative QCD calculations. Transverse energy flows in jets are studied separately for direct and resolved two-photon events. © Springer-Verlag 1997.

An updated study of B meson oscillations using dilepton events

Abstract: This paper reports a study of B meson oscillations using hadronic Z(0) decays with two identified leptons, and updates a previous publication by including data collected in 1994. Decay times are reconstructed for each of the semileptonic B decays by forming vertices which include the lepton and by estimating the B meson momentum. The mass difference, Delta m(d), between the two mass eigenstates in the B-d(0) system is measured to be 0.430 +/- 0.043 (+0.028)(-0.030) ps(-1), where the first error is statistical and the second error is systematic. For the B-s(0) system, a lower limit of Delta m(s) > 2.2 ps(-1) is obtained at 95% C.L.

Search for scalar top and scalar bottom quarks at √s = 170-172 GeV in e+e- collisions

Abstract: A search for a scalar top quark has been performed using a total data sample of 10.4 pb(-1) at centre-of-mass energies of root s=170 and 172 GeV collected with the OPAL detector at LEP. No candidate events were observed. Combining this result with those obtained at root s = 130, 136 y and 161 GeV, the 95% C.L. lower limit on the scalar top quark mass is 66.8 GeV, if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is smaller than pi/4. If the mixing angle is zero, the limit is 73.3 GeV. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark in which it decays into a bottom quark, a changed lepton and a scalar neutrino was also studied. From a similar analysis, a mass limit on the light scalar bottom quark was set at 69.7 GeV, for a mixing angle between the supersymmetric partners of the left- and right-handed states of the bottom quark of zero, and the mass difference between the scalar bottom quark and the lightest neutralino larger than 8 GeV.

A measurement of the average bottom hadron lifetime

Abstract: The average b hadron lifetime, τb, has been measured using approximately 3.5 million hadronic events collected with the OPAL detector at LEP between 1991 and 1994. A lifetime tag based on a neural network algorithm was used to select Z → bb̄ events. A secondary vertex reconstructed on the opposite side from the b-tag was used to measure the b hadron decay length. This was combined with an estimate of the b hadron momentum, allowing the b hadron decay time to be evaluated. The lifetime, τb = 1.611± 0.010 (stat)± 0.027 (syst) ps, was extracted from a fit involving the distribution of the 95 620 decay times reconstructed in the data and the corresponding distribution in Monte Carlo. (Submitted to Z. Phys. C) The OPAL Collaboration K. Ackerstaff8, G. Alexander23, J. Allison16, N. Altekamp5, K. Ametewee25, K.J. Anderson9, S. Anderson, S. Arcelli, S. Asai, D. Axen, G. Azuelos, A.H. Ball, E. Barberio, R.J. Barlow, R. Bartoldus, J.R. Batley, J. Bechtluft, C. Beeston, T. Behnke, A.N. Bell, K.W. Bell20, G. Bella23, S. Bentvelsen8, P. Berlich10, S. Bethke14, O. Biebel14, V. Blobel27, I.J. Bloodworth, J.E. Bloomer, M. Bobinski, P. Bock, H.M. Bosch, M. Boutemeur, B.T. Bouwens12, S. Braibant12, R.M. Brown20, H.J. Burckhart8, C. Burgard8, R. Bürgin10, P. Capiluppi, R.K. Carnegie, A.A. Carter, J.R. Carter, C.Y. Chang, D.G. Charlton, D. Chrisman4, P.E.L. Clarke15, I. Cohen23, J.E. Conboy15, O.C. Cooke16, M. Cuffiani2, S. Dado, C. Dallapiccola, G.M. Dallavalle, S. De Jong, L.A. del Pozo, K. Desch, M.S. Dixit7, E. do Couto e Silva12, M. Doucet18, E. Duchovni26, G. Duckeck34, I.P. Duerdoth16, J.E.G. Edwards, P.G. Estabrooks, H.G. Evans, M. Evans, F. Fabbri, P. Fath, F. Fiedler27, M. Fierro2, H.M. Fischer3, R. Folman26, D.G. Fong17, M. Foucher17, A. Fürtjes8, P. Gagnon, A. Gaidot, J.W. Gary, J. Gascon, S.M. Gascon-Shotkin, N.I. Geddes, C. Geich-Gimbel, F.X. Gentit, T. Geralis, G. Giacomelli, P. Giacomelli, R. Giacomelli, V. Gibson5, W.R. Gibson13, D.M. Gingrich30,a, D. Glenzinski9, J. Goldberg22, M.J. Goodrick5, W. Gorn, C. Grandi, E. Gross, J. Grunhaus M. Gruwé, C. Hajdu, G.G. Hanson, M. Hansroul8, M. Hapke13, C.K. Hargrove7, P.A. Hart9, C. Hartmann3, M. Hauschild8, C.M. Hawkes, R. Hawkings, R.J. Hemingway, M. Herndon, G. Herten, R.D. Heuer, M.D. Hildreth8, J.C. Hill5, S.J. Hillier1, T. Hilse10, P.R. Hobson25, R.J. Homer1, A.K. Honma, D. Horváth, R. Howard, R.E. Hughes-Jones, D.E. Hutchcroft, P. Igo-Kemenes11, D.C. Imrie25, M.R. Ingram16, K. Ishii24, A. Jawahery17, P.W. Jeffreys20, H. Jeremie, M. Jimack, A. Joly, C.R. Jones, G. Jones, M. Jones, R.W.L. Jones, U. Jost11, P. Jovanovic1, T.R. Junk8, D. Karlen6, K. Kawagoe24, T. Kawamoto24, R.K. Keeler28, R.G. Kellogg, B.W. Kennedy, B.J. King, J. Kirk, S. Kluth, T. Kobayashi, M. Kobel, D.S. Koetke, T.P. Kokott, M. Kolrep, S. Komamiya, T. Kress, P. Krieger, J. von Krogh11, P. Kyberd13, G.D. Lafferty16, H. Lafoux21, R. Lahmann17, W.P. Lai19, D. Lanske14, J. Lauber, S.R. Lautenschlager, J.G. Layter, D. Lazic, A.M. Lee, E. Lefebvre, D. Lellouch26, J. Letts2, L. Levinson26, C. Lewis15, S.L. Lloyd13, F.K. Loebinger16, G.D. Long17, M.J. Losty, J. Ludwig, A. Malik, M. Mannelli, S. Marcellini, C. Markus, A.J. Martin, J.P. Martin18, G. Martinez17, T. Mashimo24, W. Matthews25, P. Mättig3, W.J. McDonald30, J. McKenna, E.A. Mckigney, T.J. McMahon, A.I. McNab, R.A. McPherson, F. Meijers, S. Menke3, F.S. Merritt9, H. Mes7, J. Meyer27, A. Michelini2, G. Mikenberg26, D.J. Miller15, R. Mir, W. Mohr, A. Montanari, T. Mori, M. Morii, U. Müller, K. Nagai, I. Nakamura24, H.A. Neal8, B. Nellen3, B. Nijjhar16, R. Nisius8, S.W. O’Neale1, F.G. Oakham7, F. Odorici, H.O. Ogren, N.J. Oldershaw, T. Omori, M.J. Oreglia, S. Orito, J. Pálinkás, G. Pásztor, J.R. Pater, G.N. Patrick, J. Patt, M.J. Pearce, S. Petzold, P. Pfeifenschneider14, J.E. Pilcher9, J. Pinfold30, D.E. Plane8, P. Poffenberger28, B. Poli2, A. Posthaus, H. Przysiezniak, D.L. Rees, D. Rigby, S. Robertson, S.A. Robins, N. Rodning30, J.M. Roney28, A. Rooke15, E. Ros8, A.M. Rossi2, M. Rosvick28, P. Routenburg30, Y. Rozen, K. Runge, O. Runolfsson, U. Ruppel, D.R. Rust, R. Rylko, K. Sachs, E.K.G. Sarkisyan23, M. Sasaki24, C. Sbarra2, A.D. Schaile34, O. Schaile34, F. Scharf3, P. Scharff-Hansen, P. Schenk, B. Schmitt, S. Schmitt, M. Schröder, H.C. Schultz-Coulon10, M. Schulz8, M. Schumacher3, P. Schütz3, W.G. Scott20, T.G. Shears16, B.C. Shen, C.H. Shepherd-Themistocleous, P. Sherwood, G.P. Siroli, A. Sittler, A. Skillman15, A. Skuja17, A.M. Smith8, T.J. Smith28, G.A. Snow17, R. Sobie28, S. Söldner-Rembold, R.W. Springer, M. Sproston, A. Stahl, M. Steiert, K. Stephens, J. Steuerer, B. Stockhausen, D. Strom, F. Strumia, P. Szymanski, R. Tafirout,

A measurement of the charm and bottom forward-backward asymmetries using D mesons at LEP

Abstract: A measurement of the charm and bottom forward-backward asymmetry in e+e− annihilations is presented at energies on and around the peak of the Z0 resonance. Decays of the Z0 into charm and bottom quarks are tagged using D mesons identified in about 4 million hadronic decays of the Z0 boson recorded with the OPAL detector at LEP between 1990 and 1995. Approximately 33000 D mesons are tagged in seven different decay modes. From these the charm and bottom asymmetries are measured in three energy ranges around the Z0 peak: % MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXanrfitLxBI9gBaerbd9wDYLwzYbItLDharqqt% ubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq% -Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0x% fr-xfr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyuam% aaBaaaleaacaaIXaGaaGimaaqabaGccqGH9aqpciGGSbGaaiOBaiaa% ysW7caWGRbWaaSbaaSqaaiaadsfacaaIXaaabeaakiaac+cacaWGRb% WaaSbaaSqaaiaadsfacaaIYaaabeaakiabg2da9iabgkHiTmaabmaa% baGaamyramaaBaaaleaacaWGHbaabeaakiaac+cacaWGsbaacaGLOa% GaayzkaaGaey41aq7aaiWaaeaadaqadaqaaiaadsfadaWgaaWcbaGa% aGOmaaqabaGccqGHsislcaWGubWaaSbaaSqaaiaaigdaaeqaaaGcca% GLOaGaayzkaaGaai4laiaacIcacaWGubWaaSbaaSqaaiaaikdaaeqa% aOGaaGjbVlaadsfadaWgaaWcbaGaamysaaqabaGccaGGPaaacaGL7b% GaayzFaaaaaa!5C4A! $$\matrix {A_{\rm FB}^{\rm c}=0.039\pm 0.051\pm 0.009\cr A_{\rm FB}^{\rm c}=0.063\pm 0.012\pm 0.006\cr A_{\rm FB}^{\rm c}=0.158\pm 0.041\pm 0.011}$$ % MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXanrfitLxBI9gBaerbd9wDYLwzYbItLDharqqt% ubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq% -Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0x% fr-xfr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyuam% aaBaaaleaacaaIXaGaaGimaaqabaGccqGH9aqpciGGSbGaaiOBaiaa% ysW7caWGRbWaaSbaaSqaaiaadsfacaaIXaaabeaakiaac+cacaWGRb% WaaSbaaSqaaiaadsfacaaIYaaabeaakiabg2da9iabgkHiTmaabmaa% baGaamyramaaBaaaleaacaWGHbaabeaakiaac+cacaWGsbaacaGLOa% GaayzkaaGaey41aq7aaiWaaeaadaqadaqaaiaadsfadaWgaaWcbaGa% aGOmaaqabaGccqGHsislcaWGubWaaSbaaSqaaiaaigdaaeqaaaGcca% GLOaGaayzkaaGaai4laiaacIcacaWGubWaaSbaaSqaaiaaikdaaeqa% aOGaaGjbVlaadsfadaWgaaWcbaGaamysaaqabaGccaGGPaaacaGL7b% GaayzFaaaaaa!5C4A! $$\matrix {A_{\rm FB}^{\rm b}=0.086\pm 0.108\pm 0.029\cr A_{\rm FB}^{\rm b}=0.094\pm 0.027\pm 0.022\cr A_{\rm FB}^{\rm b}=0.021\pm 0.090\pm 0.026}$$ % MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXanrfitLxBI9gBaerbd9wDYLwzYbItLDharqqt% ubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq% -Jc9vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0x% fr-xfr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyuam% aaBaaaleaacaaIXaGaaGimaaqabaGccqGH9aqpciGGSbGaaiOBaiaa% ysW7caWGRbWaaSbaaSqaaiaadsfacaaIXaaabeaakiaac+cacaWGRb% WaaSbaaSqaaiaadsfacaaIYaaabeaakiabg2da9iabgkHiTmaabmaa% baGaamyramaaBaaaleaacaWGHbaabeaakiaac+cacaWGsbaacaGLOa% GaayzkaaGaey41aq7aaiWaaeaadaqadaqaaiaadsfadaWgaaWcbaGa% aGOmaaqabaGccqGHsislcaWGubWaaSbaaSqaaiaaigdaaeqaaaGcca% GLOaGaayzkaaGaai4laiaacIcacaWGubWaaSbaaSqaaiaaikdaaeqa% aOGaaGjbVlaadsfadaWgaaWcbaGaamysaaqabaGccaGGPaaacaGL7b% GaayzFaaaaaa!5C4A! $$\matrix{\langle E_{cm}\rangle =89.45\ {\rm GeV}\cr \langle E_{cm}\rangle =91.22\ {\rm GeV}\cr \langle E_{cm}\rangle =93.00\ {\rm GeV}}$$ The results are in agreement with the predictions of the standard model and other measurements at LEP.

Searches for supersymmetric particles and anomalous four-jet production at √s = 130 and 136 GeV at LEP

Abstract: A search for supersymmetric particles (charged scalar leptons, charginos decaying semileptonically, scalar top quarks) and for the associated production of two massive particles decaying into quarks has been performed using a data sample of more than 5 pb-1 at centre-of-mass energies of √s = 130 and 136 GeV collected with the OPAL detector at LEP during November 1995. No evidence for production of any of these particles has been observed in the data. Limits are presented on the production of charged scalar leptons, semileptonically decaying charginos, scalar top quarks and on the associated production of two massive particles leading to four-jet final states. © Springer-Verlag 1997.