Measurement of $\alpha_{s}$ with Radiative Hadronic Events (2009)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Hadronic final states with a hard isolated photon are studied using data taken at centre-of-mass energies around the mass of the Z0 boson with the OPAL detector at LEP. The strong coupling alpha S is...
Sub-Doppler laser spectroscopy on relativistic beams and tests of Lorentz invariance (2009)
Novotny, C., Huber, G., Karpuk, S., Reinhardt, S., Bing, D., Schwalm, D., ...
Towards a precision test of time dilation at high velocity (2009)
Novotny, C., Bernhardt, B., Bing, Dennis, Ewald, G., Geppert, C., Gwinner, G., ...
Towards a precision test of time dilation at high velocity (2009)
Novotny, C., Bernhardt, B., Bing, D., Ewald, G., Geppert, C., Gwinner, G., ...
Search for Charged Higgs Bosos in $e^{+}e^{-}$ Collisions at $\sqrt{s}$ = 189-209 GeV (2008)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
A search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at...
Search for Charged Higgs Bosos in e+e- Collisions at sqrts(s) = 189-209 GeV (2008)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
A search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at...
Beam diagnostics and adaptive optics for PHELIX (2008)
S. Borneis, E. Gaul, C. Häfner, A. Kudriaschow, T. Kühl, ...
Experiments) is designed to be a versatile laser capable of supplying a few Kilojoule, ns pulses as well as Petawatt level, fs pulses to the experiments. To achieve a focal spot size close to the...
C 3+ ion beams at the storage ring (2008)
U. Schramm, M. Bussmann, D. Habs, T. Kühl, P. Beller, B. Franzke, ...
laser and electron cooling of bunched
Measurement of the $e^+ e^- \to W^+ W^-$ cross section and W decay branching fractions at LEP (2007)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
From a total data sample of 701.1 pb^-1 recorded with e+e- centre-of-mass energies of sqrt = 161-209 GeV with the OPAL detector at LEP, 11693 W-pair candidate events are selected. These data are used...
Bose-Einstein study of position-momentum correlations of charged pions in hadronic Z0 decays (2007)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
A study of Bose-Einstein correlations in pairs of identically charged pions produced in e+e- annihilations at the Z0 peak has been performed for the first time assuming a non-static emitting source....
Extended Cluster Model for Light, and Medium Nuclei (2007)
Tomaselli, M., Kühl, T., Ursescu, D., Fritzsche, S.
The structures, the electromagnetic transitions, and the beta decay strengths of exotic nuclei are investigated within an extended cluster model. We start by deriving an effective nuclear Hamiltonian...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
A search is performed for Higgs bosons decaying into invisible final states, produced in association with a Zo boson in e+e- collisions at energies between 183 and 209 GeV. The search is based on...
Search for Dirac Magnetic Monopoles in $e^{+}e^{-}$ Collisions with the OPAL Detector at LEP2 (2007)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
This letter describes a direct search for pair produced magnetic monopoles in e+e- collisions. The analysis is based on 62.7 pb^-1 of data collected with the OPAL detector at an average...
Inclusive Jet Production in Photon-Photon Collisions at $\sqrt{^{s}ee}$ from 189 to 209 GeV (2007)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Inclusive jet production (e+e- -> e+e- +jet+X) is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies sqrt see from 189 to 209 GeV. Jets are...
Inclusive Production of Charged Hadrons in Photon-Photon Collisions (2006)
Abbiendi, G, Åkesson, P F, De Roeck, A, Zivkovic, L, Zer-Zion, D, Yamashita, S, ...
The inclusive production of charged hadrons in the collisions of quasi-real photons e+e- -> e+e- +X has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass...
Inclusive Production of Charged Hadrons in Photon-Photon Collisions (2006)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K, ...
The inclusive production of charged hadrons in the collisions of quasi-real photons e+e- -> e+e- +X has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
This paper describes a topological search for an invisibly decaying Higgs boson,H, produced via the Bjorken process (e+e- -> HZ). The analysis is based on data recorded using the OPAL detector at LEP...
QCD coherence and correlations of particles with restricted momenta in hadronic Z decays (2006)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
QCD coherence effects are studied based on measurements of correlations of particles with either restricted transverse momenta, pT
QCD coherence and correlations of particles with restricted momenta in hadronic Z decays (2006)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
QCD coherence effects are studied based on measurements of correlations of particles with either restricted transverse momenta, pT
Precision Electroweak Measurements on the Z Resonance (2006)
Schael, S, Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, ...
We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17...
Precision Electroweak Measurements on the Z Resonance (2006)
Schael, S, Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, ...
We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17...
Search for Neutral MSSM Higgs Bosons at LEP (2006)
Schael, S, Zivkovic, L, Achard, P, Adriani, O, Aguilar-Benítez, M, Alcaraz, J, ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Search for Neutral MSSM Higgs Bosons at LEP (2006)
Schael, S, Achard, P, Adriani, O, Aguilar-Benítez, M, Alcaraz, J, Alemanni, G, ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Data from e+e- annihilation into hadrons at centre-of-mass energies between 91 GeV and 209 GeV collected with the OPAL detector at LEP, are used to study the four-jet rate as a function of the Durham...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Data from e+e- annihilation into hadrons at centre-of-mass energies between 91 GeV and 209 GeV collected with the OPAL detector at LEP, are used to study the four-jet rate as a function of the Durham...
Search for neutral MSSM Higgs bosons (2006)
Achard, P., Adriani, O., Aguilar-Benítez, M., Alcaraz, J., Alemanni, G., Allaby, J., ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Search for neutral MSSM Higgs bosons (2006)
Achard, P., Adriani, O., Aguilar-Benítez, M., Alcaraz, J., Alemanni, G., Allaby, J., ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Search for neutral MSSM Higgs bosons at LEP (2006)
Achard, P., Adriani, O., Aguilar-Benítez, M., Alcaraz, J., Alemanni, G., Allaby, J., ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Experimental test of special relativity by laser spectroscopy (2006)
Novotny, C., Bernhardt, Birgitta, Ewald, G., Geppert, C., Gwinner, G., Hänsch, Theodor W., ...
Search for neutral MSSM Higgs bosons at LEP (2006)
Achard, P., Adriani, O., Aguilar-Benítez, M., Alcaraz, J., Alemanni, G., Allaby, J., ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Search for neutral MSSM Higgs bosons at LEP (2006)
Achard, P., Adriani, O., Aguilar-Benítez, M., Alcaraz, J., Alemanni, G., Allaby, J., ...
The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four...
Colour reconnection in $e^{+}e^{-}\to W^{+}W^{-}$ at $\sqrt{s}$ = 189 - 209 GeV$ (2005)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
The effects of the final state interaction phenomenon known as colour reconnection are investigated at centre-of-mass energies in the range $\sqrt{s}~ 189-209 GeV using the OPAL detector at LEP....
Measurement of the mass and width of the W boson (2005)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
The mass and width of the W boson are measured using e+e- -> W+W- events from the data sample collected by the OPAL experiment at LEP at centre-of-mass energies between 170 GeV and 209 GeV. The mass...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Searches were performed for topologies predicted by gauge-mediated Supersymmetry breaking models (GMSB). All possible lifetimes of the next-to-lightest SUSY particle (NLSP), either the lightest...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Searches were performed for topologies predicted by gauge-mediated Supersymmetry breaking models (GMSB). All possible lifetimes of the next-to-lightest SUSY particle (NLSP), either the lightest...
Determination of $\alpha_{s}$ using Jet Rates at LEP with the OPAL detector (2005)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Hadronic events produced in e+e- collisions by the LEP collider and recorded by the OPAL detector were used to form distributions based on the number of reconstructed jets. The data were collected...
Determination of $\alpha_{s}$ using Jet Rates at LEP with the OPAL detector (2005)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Hadronic events produced in e+e- collisions by the LEP collider and recorded by the OPAL detector were used to form distributions based on the number of reconstructed jets. The data were collected...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
For the first time at LEP the production of prompt photons is studied in the collisions of quasi-real photons using the OPAL data taken at e+e- centre-of-mass energies between 183 GeV and 209 GeV....
Measurement of the running of the QED coupling in small-angle Bhabha scattering at LEP (2005)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Using the OPAL detector at LEP, the running of the effective QED coupling alpha(t) is measured for space-like momentum transfer through its effect on the angular spectrum of small-angle Bhabha...
Measurement of the running of the QED coupling in small-angle Bhabha scattering at LEP (2005)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Anagnostou, G, Anderson, K J, ...
Using the OPAL detector at LEP, the running of the effective QED coupling alpha(t) is measured for space-like momentum transfer through its effect on the angular spectrum of small-angle Bhabha...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A study of Z-boson pair production in e+e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nn), quark and...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A study of Z-boson pair production in e+e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nn), quark and...
Challenges and opportunities for atomic physics at FAIR: The new GSI accelerator project (2005)
Hagmann, S., Beyer, H. F., Bosch, F., Bräuning-Demian, A., Kluge, H. J., Kozhuharov, C., ...
We present a short overview of the current status of the new accelerator project FAIR at GSI with the new double synchrotron rings and the multi-storage rings. The key features of the new facility,...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
We have studied hadronic events from e+e- annihilation data at centre-of-mass energies from 91 to 209 GeV. We present distributions of event shape observables and their moments at each energy and...
Measurement of $R_b$ in $e^+ e^-$ Collisions at 182 - 209 GeV (2004)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Measurements of Rb, the ratio of the bbbar cross-section to the qqbar cross- section in e+e- collisions, are presented. The data were collected by the OPAL experiment at LEP at centre-of-mass...
Search for Radions at LEP2 (2004)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A new scalar resonance, called the radion, with couplings to fermions and bosons similar to those of the Higgs boson, is predicted in the framework of Randall-Sundrum models, proposed solutions to...
Determination of the LEP Beam Energy using Radiative Fermion-pair Events, 2004 (2004)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
We present a determination of the LEP beam energy using "radiative return" fermion-pair events recorded at centre-of-mass energies from 183 GeV to 209 GeV. We find no evidence of a disagreement...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Upper limits on the cross-section of the pair-production process e+e- -> h0A0 assuming 100% decays into hadrons, are derived from a new search for the h0A0 -> hadrons topology, independent of the...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Events with a final state consisting of two or more photons and large missing transverse energy have been observed in e+e- collisions at centre-of-mass energies in the range 192 - 209 GeV using the...
Search for neutral Higgs bosons in CP-conserving and CP-violating MSSM scenarios (2004)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
This report summarizes the final results from the OPAL collaboration on searches for neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model (MSSM). CP-conserving and for the...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Flavour inclusive, udsc and b fragmentation functions in unbiased jets, and flavour inclusive, udsc, b and gluon fragmentation functions in biased jets are measured in e+e- annihilations from data...
Measurement of the Strange Spectral Function in Hadronic $\tau$ Decays (2004)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Tau Lepton decays with open strangeness in the final state are measured with the OPAL detector at LEP to determine the strange hadronic spectral function of the tau lepton. The decays tau- ->...
Study of Bose-Einstein Correlations in $e^{+}e^{-}\to W^{+}W^{-}$ events at LEP (2004)
Abbiendi, G, Ainsley, C, Åkesson, T, Alexander, G, Allison, J, Amaral, P, ...
Bose-Einstein correlation between like-sign charged-particle pairs in e+e- -> W+W- events recorded with the OPAL detector at LEP at centre-of-mass energies between 183 GeV and 209 GeV are studied....
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Anomalous quartic couplings between the electroweak gauge bosons may contribute to the vv gamma gamma and qq gamma gamma final states produced in e+e- collisions. This analysis uses the LEP2 OPAL...
Search for Chargino and Neutralino Production at $\sqrt{s}$ = 192-209 GeV at LEP (2004)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Approximately 438 pb-1 of e+e- data from the OPAL detector, taken with the LEP collider running at centre-of-mass energies of 192-209 Gev, are analyzed to search for evidence of chargino pair...
Laser Cooling and Spectroscopy of Relativistic C 3+ Beams at the ESR ∗ (2004)
U. Schramm, M. Bussmann, D. Habs, M. Steck, T. Kühl, K. Beckert, ...
Abstract. We report on the first laser cooling of a bunched beam of multiply charged C 3+ ions performed at the ESR (GSI) at a beam energy of E = 1.47 GeV. Moderate bunching provided a force...
W Boson Polarisation at LEP2 (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Elements of the spin density matrix for W bosons in e+e- -> W+W- -> qqln events are measured from data recorded by the OPAL detector at LEP. This information is used calculate polarised differential...
Measurement of the partial widths of the Z into up- and down-type quarks (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
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....
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
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 ATLAS Silicon Pixel Sensors (2003)
Alam, M S, Ciocio, A, Einsweiler, K F, Emes, J, Gilchriese, M G D, Joshi, A, ...
Prototype sensors for the ATLAS silicon pixel detector have been developed. The design of the sensors is guided by the need to operate them in the severe LHC radiation environment at up to several...
Search for R-parity violating decays of sfermions at LEP (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A search for pair-produced scalar fermions under the assumption that R-parity is not conserved has been performed using data collected with the OPAL detector at LEP. The data samples analysed...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
We present the first experimental results based on the jet boost algorithm, a technique to select unbiased samples of gluon jets in e+e- annihilations, i.e. gluon jets free of biases introduced by...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A study of Z-boson pair production in e+e- annihilation at center-of-mass energies between 190 GeV and 209 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nn), quark and...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP,...
A Study of $W^{+}W^{-}\gamma$ Events at LEP (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A study of W+W- events accomanied by hard photon radiation 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...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
In total 1317 di-lepton events with significant missing transverse momentum were identified in a total data sample of 680 pb-1 collected at e+e- centre-of-mass energies ranging from 183 GeV to 209...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A search for single production of doubly-charged Higgs bosons has been performed using 600.7 pb^-1 of e+e- collision data with sqrt(s)=189--209GeV collected by the OPAL detector at LEP. No evidence...
A study of charm production in beauty decays with the OPAL detector at LEP (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Using an inclusive method, BR(b -> D\bar{D}X) has been measured in hadronic Z^0 decays with the OPAL detector at LEP. The impact parameter significance of tracks opposite tagged b-jets is used to...
Measurement of charged current triple gauge boson couplings using W pairs at LEP (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Triple gauge boson couplings are measured from W-pair and single photon events recorded by the OPAL detector at LEP at center-of-mass energies between 183 - 209 GeV with a total integrated luminosity...
Abbiendi, G, Carter, A, De Wolf, E, McPherson, R A, Neal, H, Thomson, M, ...
Hadronic Z0 decays with identified electrons or muons have been used to measure the forward-backward asymmetries of e^+e^- --> Z0 --> bbbar and e^+e^- --> Z0 --> ccbar events. The asymmetries at...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
Gluon jets with a mean energy of 22 GeV and purity of 95% are selected from hadronic Z0 decay events produced in e+e- annihilations. A subsample of these jets is identified which exhibits a large gap...
Abbiendi, G, Ainsley, C, Alexander, G, Åkesson, P F, Allison, J, Amaral, P, ...
For the first time at LEP the production of prompt photons is studied in the collisions of quasi-real photons using the OPAL data taken at e+e- centre-of-mass energies between 183 GeV and 209 GeV....
Abbiendi, G, Ainsley, C, Alexander, G, Åkesson, P F, Allison, J, Amaral, P, ...
For the first time at LEP the production of prompt photons is studied in the collisions of quasi-real photons using the OPAL data taken at e+e- centre-of-mass energies between 183 GeV and 209 GeV....
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, G, Allison, J, Amaral, P, ...
A search for pair-produced leptoquarks is performed using e+e- collision events collected by the OPAL detector at LEP at centre-of-mass energies between 189 and 209 GeV. The data sample corresponds...
Abbiendi, G, Ainsley, C, Alexander, G, Allison, J, Amaral, P, Anagnostou, G, ...
A search for stable and long-lived massive particles of electric charge |Q/e|=1 or fractional charges of 2/3, 4/3, and 5/3 is reported using data collected by the OPAL detector at LEP, at...
Test of non-commutative QED in the process $e^{+}e^{-} \to \gamma \gamma$ at LEP (2003)
Abbiendi, G, Ainsley, C, Alexander, G, Allison, J, Amaral, P, Anagnostou, G, ...
Non-communicative QED would lead to deviations from the Standard Model depending on a new energy scale $\Delta_{NC}$ and a unique direction in space defined by two angles $\eta$ and $\xi$. Here in...
Bose-Einstein Correlations of $\pi^{0}$ Pairs from Hadronic $Z^{0}$ Decays (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Amaral, P, ...
We observed Bose-Einstein correlation in pi0 pairs produced in Z0 decays using the data sample collected by the OPAL detector at LEP 1 from 1991 to 1995. Using a static Gaussian picture for the pion...
A Measurement of Semileptonic B Decays to Narrow Orbitally-Excited Charm Mesons (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Amaral, P, ...
The decay chain b -> Bbar -> D^{**0} l nu X, D^{**0} -> D^{*+} pi^-, D^{*+} -> D^0 pi^+, D^0 ->(Kpi or K3pi) is identified in a sample of 3.9 million hadronic Z decays collected with the OPAL...
Di-Jet Production in Photon-Photon colisions at $\sqrt{s_{ee}}$ from 189 to 209 GeV (2003)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Amaral, P, ...
Di-jet producion is studied in collisions of quasi-real photons at e+e- centre- of-mass energies sqrt(s)ee from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are...
A Measurement of the $\tau^{-}\to \mu^{-}\overline{\nu}_{\mu}\nu_{\tau}$ Branching Ratio (2002)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Amaral, P, ...
The tau -> mu nu nu 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(tau -> mu nu nu) = 0.1734 +-...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
A novel method of determining the mass of the W boson in the W+W- -> lnu lnu channel is presented and applied to 667pb^-1 of data recorded at the center-of- mass energies in the range 183-207 GeV...
Measurement of the Hadronic Photon Structure Function $F_{2}^{\gamma}$ at LEP2 (2002)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
The hadronic structure of the photon F2gamma is measured as a function of Bjorken x and of the photon virtuality Q2 using deep-inelastic scattering data taken by the OPAL detector at LEP at e+e-...
Search for Leptoquarks in Electron-Photon Scattering at $\sqrt{s_{ee}}$ up to 209 GeV at LEP (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Searches for first generation scalar and vector leptoquarks, and for squarks in R-parity violating SUSY models with the direct decay of the squark into Standard Model particles, have been performed...
Search for Doubly Charged Higgs Bosons with the OPAL detector at LEP (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
A search for pair-produced doubly charged Higgs bosons has been performed using data samples corresponding to an integrated luminosity of about 614 pb-1 collected with the OPAL detector at LEP at...
Particle multiplicity of unbiased gluon jets from $e^+ e^-$ three-jet events (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
The charged particle multiplicities of two- and three-jet events from the reaction e+e- -> Z0 -> hadrons are measured for Z0 decays to light quark (uds) flavors. Using recent theoretical expressions...
Search for Yukawa Production of a Light Neutral Higgs Boson at LEP (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Within a Two-Higgs-Doublet Model (2HDM) a search for a light Higgs boson in the mass range of 4-12 GeV has been performed in the Yukawa process e+e- -> b bbar A/h -> b bbar tau+tau-, using the data...
Genuine Correlations of Like-Sign Particles in Hadronic $Z^0$ Decays (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Correlations among hadrons with the same electric charge produced in Z0 decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized...
Search for Single Top Quark Production at LEP2 (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
A search for single top quark production via flavour changing neutral currents (FCNC) was performed with data collected by the OPAL detector at the e+e- collider LEP. Approximately 600 pb-1 of data...
Measurement of the Hadronic Cross-Section for the Scattering of Two Virtual Photons at LEP (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
The interaction of virtual photons is investigated using the reaction e+e- -> e+e- hadrons based on data taken by the OPAL experiment at e+e- centre-of-mass energies sqrt(s_ee)=189-209 GeV, for W>5...
Measurement of $Z/\gamma^{*}$ production in Compton scattering of quasi-real photons (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
The process e+ e- -> e+ e- Z/gamma* is studied with the OPAL detector at LEP at a centre of mass energy of sqrt(s) = 189 GeV. The cross-section times the branching ratio of the Z/gamma* decaying into...
Determination of the b Quark Mass at the Z Mass Scale (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
In hadronic decays of Z bosons recorded with the OPAL detector at LEP, events containing b quarks were selected using the long lifetime of b flavoured hadrons. Comparing the 3-jet rate in b events...
Search for Lepton Flavour Violation in $e^+e^-$ Collisions at $\sqrt{s}$ = 189 - 209 GeV (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
We search for lepton flavour violating events (e mu, e tau and mu tau) that could be directly produced in e+e- annihilations, using the full available data sample collected with the OPAL detector at...
Measurement of the Branching Ratio for the Process $b \to \tau^{-}\overline{\nu}_{\tau}X$ (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
The inclusive branching ratio for the process b -> tau nu X has been measured using hadronic Z decays collected by the OPAL experiment at LEP in the years 1992-2000. The result is: BR(b -> tau nu X)...
Angular Analysis of the Muon Pair Asymmetry at LEP 1 (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Data on muon pair production obtained by the OPAL collaboration at centre of mass energies near the Z peak are analysed. Small angular mismatches between the directions of the two muons are used to...
Measurement of |$V_{ub}$| using b hadron semileptonic decays (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
The magnitude of the CKM matrix element Vub is determined by measuring the inclusive charmless semileptonic branching fraction of beauty hadrons at OPAL based on b -> Xu l nu event topology and...
Abbiendi, G, Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
A search for first generation scalar and vector leptoquarks (LQ) as well as for squarks in R-parity violating SUSY models has been performed using e+e- collisions collected with the OPAL detector at...
Precision Neutral Current Asymmetry Parameter Measurements from the Tau Polarization at LEP (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Measurements of the tau lepton polarization and forward-backward polarization asymmetry near the Z resonance using the OPAL detector are described. The measurements are based on analyses of tau -> e...
Measurement of the Branching Ratio for $D_{s} \to \tau\nu_{\tau}$ Decays (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Using about 3.9 million hadronic Z decays from e+e- collisions recorded by the OPAL detector at LEP at centre-of-mass energies near MZ the branching ratio for the decay D_s -> tau nu_tau has been...
A Simultaneous Measurement of the QCD Colour Factors and the Strong Coupling (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
Using data from e+e- annihilation into hadrons, taken with the OPAL detector at LEP at the Z pole between 1991 and 1995, we performed a simultaneous measurement of the colour factors of the...
A Search for a Narrow Radial Excitation of the $D^{*\pm}$ Meson (2001)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
A sample of 3.73 million hadronic Z decays, recorded with the OPAL detector at LEP in the years 1991-95, has been used to search for a narrow resonance corresponding to the decay of the D*'+/-(2629)...
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
A search for the Standard Model Higgs boson has been performed with the OPAL detector at LEP based on the full data sample collected at sqrt(s) = 192-209 GeV in 1999 and 2000, corresponding to an...
Precise Determination of the Z Resonance Parameters at LEP: Zedometry (2000)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
This final analysis of hadronic and leptonic cross-sections and of leptonic forward-backward asymmetries in e+e- collisions with the OPAL detector makes use of the full LEP1 data sample comprising...
A Study of $B_{s}$ Meson Oscillation Using $D_{s}^{-}$-Lepton Correlations (2000)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
From data collected around the Z resonance by the OPAL detector at LEP a sample of Bs decays was obtained using Ds^-l^+ combinations, where the Ds^- was fully reconstructed in the phi pi-, K*0K- and...
Charged Multiplicities in Z Decays into u, d, and s Quarks (2000)
Abbiendi, G, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, Anagnostou, G, ...
About 4.4 million hadronic decays of Z bosons, recorded by the OPAL detector at LEP at a centre-of-mass energy of around sqrt(s) = 91.2 GeV, are used to determine the mean charged particle...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
The rates are measured per hadronic Z decay for gluon splitting to bb(bar) quark pairs, g_bb, and of events containing two bb(bar) quark pairs, g_4b, using a sample of four-jet events selected from...
Abbiendi, G, Abbiendi, G, Ackerstaff, K, Ainsley, C, Alexander, Gideon, Allison, J, ...
From about 4 million hadronic Z decays recorded by the OPAL detector on and near to the Z resonance, we select a sample of more than 570000 inclusively reconstructed B mesons. Orbitally-excited...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
The lifetime and oscillation frequency of the B0 meson has been measured using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP. The D*+ -> D0pi+ decays were reconstructed...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
A measurement of triple gauge boson couplings is presented, based on W-pair data recorded by the OPAL detector at LEP during 1998 at a centre-of-mass energy of 189 GeV with an integrated luminosity...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
From a data sample of 183 pb^-1 recorded at a center-of-mass energy of roots = 189 GeV with the OPAL detector at LEP, 3068 W-pair candidate events are selected. Assuming Standard Model W boson decay...
A Measurement of the Rate of Charm Production in W Decays (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
Using data recorded at centre-of-mass energies around 183 GeV and 189 GeV with the OPAL detector at LEP, the fundamental coupling of the charm quark to the W boson has been studied. The ratio Rc^W =...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
Measurements are presented of the polarisation of W+W- boson pairs produced in e+e- collisions, and of CP-violating WWZ and WWGamma trilinear gauge couplings. The data were recorded by the OPAL...
A Study of One-Prong Tau Decays with a Charged Kaon (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
From an analysis of the ionisation energy loss of charged particles selected from 110326 e+e- -> tau+tau- candidates recorded by the OPAL detector at e+e- centre-of-mass energies near the Z0...
Measurement of the Mass and Width of the W Boson in $e^{+}e^{-}$ Collisions at 189 GeV (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
The mass and width of the W boson are determined in e+e- collisions at LEP using 183 pb^-1 of data recorded at a centre-of-mass energy roots=189 GeV with the OPAL detector. The invariant mass...
Two Higgs Doublet Model and Model Independent Interpretation of Neutral Higgs Boson Searches (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
Searches for the neutral Higgs bosons h0 and A0, are used to obtain limits on the Type II Two Higgs Doublet Model (2HDM(II)) with no CP-violation in the Higgs sector and no additional particles...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
The inclusive production rate of phi mesons from the decay of b hadrons produced in Z0 decays was measured to be Br(b->phi+X) = 0.0282+-0.0013(stat.)+-0.0019(syst.), using data collected by the OPAL...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
The data recorded at a centre-of-mass energy of 189GeV by the OPAL detector at LEP are used to search for trilinear couplings of the neutral gauge bosons in the process e+e- --> Z-gamma. The...
Multiplicities of $\pi^{0}$, $\eta$, $K^{0}$ and of charged particles in quark and gluon jets (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
We compared the multiplicities of pizero, eta, Kzero and of charged particles in quark and gluon jets in 3-jet events, as measured by the OPAL experiment at LEP. The comparisons were performed for...
Measurement of the Low-x Behaviour of the Photon Structure Function $F2-\gamma$ (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
The photon structure function F2-gamma(x,Q**2) has been measured using data taken by the OPAL detector at centre-of-mass energies of 91Gev, 183Gev and 189Gev, in Q**2 ranges of 1.5 to 30.0 GeV**2...
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
Searches for final states expected in models with light gravitinos have been performed, including experimental topologies with multi-leptons with missing energy, leptons and photons with missing...
A measurement of the $\tau$ mass and the first CPT test with $\tau$ leptons (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(sys t.) MeV using tau pairs from Z0 decays. To test CPT invariance we compare the masses of the positively and negatively charged...
Photonic events with missing energy in $e^{+}e^{-}$ collisions at $\sqrt{s}=189 GeV$ (2000)
Abbiendi, G, Ackerstaff, K, Ainsley, C, Åkesson, P F, Alexander, Gideon, Allison, J, ...
Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 189GeV using the OPAL detector at LEP. Results are presented for event topologies...
Z boson pair production in $e^{+}e^{-}$ collisions at $\sqrt{s}$ = 183 and 189 GeV (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
A study of Z boson pair production in e+e- annihilation at center-of-mass energies near 183 GeV and 189 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nu nubar), quark and...
Measurement of |$V_{cb}$| using $\overline{B}^{0} \to D^{*+}l^{-}\overline{\nu}$ decays (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
The magnitude of the Cabibbo-Kobayashi-Maskawa matrix element Vcb has been measured using B0 to D*l nu decays recorded on the Z0 peak using the OPAL detector at LEP. The D* to D0 pi+ decays were...
Transverse and Longitudinal Bose Einstein Correlations in hadronic $Z^0$ Decays (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
Bose-Einstein correlations in pairs of identical charged pions produced in asample of 4.3 million Z0 hadronic decays are studied as a function of the threecomponents of the momentum difference,...
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
The cross-section ratio Rb=sigma(e+e- to b-antib)/sigma(e+e- to q-antiq) andthe bottom and charm forward-backward asymmetries AFB^b and AFB^c are measuredusing event samples collected by the OPAL...
Search for new Physics in rare B Decays (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
A search for the decay B+- to K+-K+-pi-+ was performed using data collected by the OPAL detector at LEP. These decays are strongly suppressed in the Standard Model but could occur with a higher...
QCD studies with $e^{+}e^{-}$ annihilation data at 172-189 GeV (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
We have studied hadronic events from e+e- annihilation data at centre-of-mass energies of sqrt{s}=172, 183 and 189 GeV. The total integrated luminosity of the three samples, measured with the OPAL...
Search for new Physics in rare B Decays (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
A search for the decay B+- to K+-K+-pi-+ was performed using data collected by the OPAL detector at LEP. These decays are strongly suppressed in the Standard Model but could occur with a higher...
Leading Particle Production in Light Flavour Jets (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
The energy distribution and type of the particle with the highest momentum in quark jets are determined for each of the five quark flavours making only minimal model assumptions. The analysis is...
Pfeifenschneider, P, Biebel, O, Movilla-Fernández, P A, Abbiendi, G, Ackerstaff, K, Åkesson, P F, ...
We employ data taken by the JADE and OPAL experiments for an integrated QCD study in hadronic e+e- annihilations at c.m.s. energies ranging from 35 GeV through 189 GeV. The study is based on...
Search for Unstable Heavy and Excited Leptons at LEP2 (2000)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
Searches for unstable neutral and charged heavy leptons, N and L+-, and for excited states of neutral and charged leptons, nu*, e*, mu*, and tau*, have been performed in e+e- collisions using data...
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
Bose-Einstein correlations in pairs of charged kaons produced in a sample of 3.9 million hadronic Z0 decays have been measured with the OPAL experiment at LEP. Charged kaons were identified in the...
$\tau$ decays with neutral kaons (1999)
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
The branching ratio of the tau lepton to a neutral K meson is measured from a sample of approximately 200,000 tau decays recorded by the OPAL detector at centre-of-mass energies near the Z0...
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
The inclusive production of D*+- mesons in photon-photon collisions has been measured using the OPAL detector at LEP at e+e- centre-of-mass energies of 183 and 189GeV. The D* mesons are reconstructed...
Abbiendi, G, Ackerstaff, K, Åkesson, P F, Alexander, Gideon, Allison, J, Anderson, K J, ...
A study of W+W- events accompanied by hard photon radiation produced in e+e- collisions at LEP is presented. Events consistent with two on-shell W-bosons and an isolated photon are selected from...
Precision Luminosity for $Z^{0}$ Lineshape Measurements with a Silicon-Tungsten Calorimeter (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
The measurement of small-angle Bhabha scattering is used to determine the luminosity at the OPAL interaction point for the LEP I data recorded between 1993 and 1995. The measurement is based on the...
Search for Chargino and Neutralino Production at $\sqrt{s} = 189 GeV$ at LEP (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
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....
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 237.4 pb-1 at e+e- centre-of-mass energies of 183 GeV and 189 GeV. The...
A Study of Three-Prong $\tau$ Decays with Charged Kaons (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
From an analysis of the ionisation energy loss of charged particles selected from a sample of 147926 e+e- -> tau+tau- candidates recorded in the OPAL detector at e+e- centre-of-mass energies near the...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
A search for pair-produced leptoquarks has been performed using a sample of e+e- collision events collected by the OPAL detector at LEP at e+e- centre-of-mass energies of about 183 GeV. The data...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
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...
Search for Neutral Higgs Bosons in $e^{+}e^{-}$ Collisions at $\sqrt{s} \sim$ 189 GeV (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
A search for neutral Higgs bosons has been performed with the OPAL detector at LEP, using approximately 170 pb-1 of e+e- collision data collected at sqrt(s)~189GeV. Searches have been performed for...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
The rate of secondary charm-quark-pair production has been measured in 4.4 million hadronic Z0 decays collected by OPAL. By selecting events with three jets and tagging charmed hadrons in the gluon...
Multi-photon production in $e^{+}e^{-}$ collisions at $\sqrt{s}$ = 189 GeV (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Anderson, K J, Anderson, S, ...
The process e+e- to 2 (or 3) gammas is studied using data recorded with the OPAL detector at LEP. The data sample taken at a centre-of-mass energy of 189 GeV corresponds to a total integrated...
A study of $B^{0}_{s}$ meson oscillation using hadronic $Z^{0}$ decays containing leptons (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A sample of Z decays containing b-flavoured hadrons is tagged using leptons, and events having precise proper time measurements are selected. These events are used to study Bs oscillations. using the...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A search is described for the generic process e+e- to X Y, where X is a neutral heavy scalar boson decaying into a pair of photons, and Y is a neutral heavy boson (scalar or vector) decaying into a...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The helicity density matrix elements rho[00] of rho(770)+- and omega(782) mesons produced in Z decays have been measured using the OPAL detector at LEP. Over the measured meson energy range, the...
Measurements of inclusive semileptonic branching fractions of b hadrons in $Z^{0}$ decays (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A measurement of inclusive semileptonic branching fractions of b hadrons produced in Z decays is presented. An enriched Z -> bbbar sample is obtained with a lifetime flavour-tagging technique. The...
Total Hadronic Cross-Section of Photon-Photon Interactions at LEP (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The total hadronic cross-section sigma_gg(W) for the interaction of real photons, gg->hadrons, is measured for gg centre-of-mass energies 10 e+e- hardrons, using a luminosity function for the photon...
Search for R-Parity Violating Decays of Scalar Fermions at LEP (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A search for pair produced scalar fermions with couplings that violate R-parity has been performed using a data sample corresponding to an integrated luminosity of 56 pb-1 at a centre-of-mass energy...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
We present a test of the flavour independence of the strong coupling constant for charm and bottom quarks with respect to light (uds) quarks, based on a hadronic event sample obtained with the OPAL...
Search for Scalar Top and Scalar Bottom Quarks at $\sqrt{s}$ = 189 GeV at LEP (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Searches for a scalar top quark and a scalar bottom quark have been performed using a data sample of 182 pb-1 at a centre-of-mass energy of 189 GeV collected with the OPAL detector at LEP. No...
Experimental properties of gluon and quark jets from a point source (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Gluon jets are identified in hadronic Z0 decays as all the particles in a hemisphere opposite to a hemisphere containing two tagged quark jets. Gluon jets defined in this manner are equivalent to...
Intermittency and correlations in hadronic $Z^0$ decays (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A multidimensional study of local multiplicity fluctuations and multiparticle correlations of hadrons produced in Z decays is performed. The study is based on the data sample of more than 4 million...
PHELIX: Petawatt High Energy Laser for heavy-Ion eXperiments (1999)
Backe, H, Böck, R K, Caird, J, Fill, E, Habs, D, Hoffmann, Dieter H H, ...
Measurements of the QED Structure of the Photon (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The structure of both quasi-real and highly virtual photons is investigated using the reaction e+e- -> e+e-mu+mu-, proceeding via the exchange of two photons. The results are based on the complete...
Searches for R-Parity Violating Decays of Gauginos at 183 GeV at LEP (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Searches for pair-produced charginos and neutralinos with R-parity violating decays have been performed using a data sample corresponding to an integrated luminosity of 56 pb-1 collected with the...
Measurement of the W Mass and Width in $e^{+}e^{-}$ Collisions at 183 GeV (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Using a data sample of 57 pb-1 recorded at a centre-of-mass energy of 183 GeV with the Opal detector at LEP, 282 W+W- -> qqqq and 300 W+W- -> qqlnu candidate events are used to obtain a measurement...
Colour reconnection studies in $e^{+}e^{-} \to W^{+}W^{-}$ at $\sqrt{s}$=183 GeV (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The predicted effects of final state interactions such as colour reconnection are investigated by measuring properties of hadronic decays of W bosons, recorded at a centre-of-mass energy of...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The lifetimes of the B+ and B0 mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic Z0 decays recorded at LEP. Z0 -> b bbar decays were tagged using displaced...
Search for Baryon and Lepton Number Violating $Z^0$ Decays (1999)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Using data collected with the OPAL detector at LEP, we have searched for the processes e+e- -> Z0 -> p e-, p mu- and the charge conjugate final-states. These would violate the conservation of the...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the...
A measurement of the $\tau^{-} \to e^{-} \overline{\nu}_{e}\nu_{\tau}$ branching ratio (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The branching ratio for the decay tau->e nue nutau has been measured using Z0 decay data collected by the OPAL experiment at LEP. In total 33073 tau->e nue nutau candidates were identified from a...
$W^{+}W^{-}$ production and triple gauge boson couplings at LEP energies up to 183 GeV (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A study of W-pair production in e+e- annihilations at Lep2 is presented, based on 877 W+W- candidates corresponding to an integrated luminosity of 57 pb-1 at sqrt(s) = 183 GeV. Assuming that the...
Search for Higgs Bosons in $e^{+} e^{-}$ Collisions at 183 GeV (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs...
Bose-Einstein Correlations in $e^{+} e^{-} \to W^{+}W^{-}$ at 172 and 183 GeV (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Bose-Einstein correlations between like-charge pions are studied in hadronic final states produced by e+e- annihilations at center-of-mass energies of 172 and 183 GeV. Three event samples are...
A Measurement of $R_{b}$ using a Double Tagging Method (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The fraction of Z to bbbar events in hadronic Z decays has been measured by the OPAL experiment using the data collected at LEP between 1992 and 1995. The Z to bbbar decays were tagged using...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Photonic events with large missing energy have been observed in e+e- collisions at centre-of-mass energies of 130, 136 and 183 GeV collected in 1997 using the OPAL detector at LEP. Results are...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The inclusive charm hadron semileptonic branching fractions B(c to e) and B(c to mu) in Z to ccbar events have been determined using 4.4 million hadronic Z decays collected with the OPAL detector at...
Search for Chargino and Neutralino Production at $\sqrt{s}$ = 181-184 GeV at LEP (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A search for charginos and neutralinos, predicted by supersymmetric theories, has been performed using a data sample of 57 pb-1 at centre-of-mass energies of 181-184 GeV taken with the OPAL detector...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
In the process e+e- to hadrons, one of the effects of gluon emission is to modify the 1+cos(theta)**2 form of the angular distribution of the thrust axis, an effect which may be quantified by the...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 77.0 pb-1 at e+e- centre-of-mass energies of 161 GeV, 172 GeV and 183 GeV....
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
The correlated production of Lambda and Lambdabar baryons has been studied using 4.3 million multihadronic Zo decays recorded with the OPAL detector at LEP. Di-lambda pairs were investigated in the...
First measurement of $Z/\gamma^{*}$ production in Compton scattering of quasi-real photons (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons...
Di-Jet Production in Photon-Photon Collisions at $\sqrt{s}_{ee}$ = 161 and 172 GeV (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Di-jet production is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies 161 and 172 GeV. The jets are reconstructed using a cone jet finding...
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
Cross-sections for hadronic, b-bbar and lepton pair final states in e+e- collisions at sqrt(s) = 183 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of...
Measurement of the average polarization of b baryons in hadronic $Z^0$ decays (1998)
Abbiendi, G, Ackerstaff, K, Alexander, Gideon, Allison, J, Altekamp, N, Anderson, K J, ...
In the Standard Model, b quarks produced in e^+e^- annihilation at the Z^0 peak have a large average longitudinal polarization of -0.94. Some fraction of this polarization is expected to be...
Shabaev, V. M., Shabaeva, M. B., Tupitsyn, I. I., Yerokhin, V. A., Artemyev, A. N., Kühl, T., ...
The ground state hyperfine splitting values and the transition probabilities between the hyperfine structure components of high Z lithiumlike ions are calculated in the range $Z=49-83$. The...
Ground state hyperfine splitting of high Z hydrogenlike ions (1997)
Shabaev, V. M., Tomaselli, M., Kühl, T., Artemyev, A. N., Yerokhin, V. A.
The ground state hyperfine splitting values of high Z hydrogenlike ions are calculated. The relativistic, nuclear and QED corrections are taken into account. The nuclear magnetization distribution...
Boos, N, Le Blanc, F, Krieg, M, Pinard, J, Huber, G, Lunney, M D, ...
A test of special relativity with stored lithium ions (1994)
Grieser, R, Klein, R, Huber, G, Dickopf, S, Klaft, I, Knobloch, P, ...
Eberz, J, Dinger, U, Huber, G, Lochmann, H, Menges, R, Neugart, R, ...