Search for Scalar Top and Scalar Bottom Quarks at sqrt(s) = 183 GeV at LEP (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Searches for a scalar top quark and a scalar bottom quark have been performed using a total data sample of 56.8 pb-1 at a centre-of-mass energy of 183 GeV collected with the OPAL detector at LEP. No...
Production of Chi_c2 Mesons in Photon-Photon Collisions at LEP (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
We present an observation at LEP of the production of chi_c2 mesons in the collisions of two quasi-real photons using the OPAL detector. The chi_c2 mesons are reconstructed in the decay channel...
Collaboration, The OPAL, Al, K. Ackerstaff Et
The spectral functions of the vector current and the axial-vector current have been measured in hadronic tau decays using the OPAL detector at LEP. Within the framework of the Operator Product...
Measurement of the Michel Parameters in Leptonic Tau Decays (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The Michel parameters of the leptonic tau decays are measured using the OPAL detector at LEP. The Michel parameters are extracted from the energy spectra of the charged decay leptons and from their...
Search for Higgs Bosons and New Particles Decaying into Two Photons at sqrt(s) = 183 GeV (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
A search for the resonant production of high mass photon pairs associated with a leptonic or hadronic system has been performed using a data sample of 57.7 pb-1 collected at an average center-of-mass...
Multi-photon production in e+e- collisions at sqrt(s) = 183 GeV (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The process e+e- to gamma gamma (gamma) 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...
Measurement of Tau Branching Ratios to Five Charged Hadrons (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The branching ratios of the decay of the tau lepton to five charged hadrons have been measured with the OPAL detector at LEP using data collected between 1991 and 1995 at e+e- centre-of-mass energies...
Inclusive Production of Charged Hadrons and K_s Mesons in Photon-Photon Collisions (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The production of charged hadrons and K_s mesons in the collisions of quasi-real photons has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass energies of 161...
Measurements of Flavour Dependent Fragmentation Functions in Z^0 -> qq(bar) Events (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Fragmentation functions for charged particles in Z -> qq(bar) events have been measured for bottom (b), charm (c) and light (uds) quarks as well as for all flavours together. The results are based on...
Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected...
An upper limit for the tau-neutrino mass from tau --> 5 pi+- nu_tau decays (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
An upper limit for the tau-neutrino mass has been determined from the decay tau -> 5pi+- \nu_tau using data collected with the OPAL detector from 1991 to 1995 in e+e- collisions at \sqrt{s} ~ M_Z. A...
Production of K^0_S and Lambda in Quark and Gluon Jets from Z^0 Decay (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The production of K^0_S mesons and Lambda baryons in quark and gluon jets has been investigated using two complementary techniques. In the first approach, which provides high statistical accuracy,...
Photon and Light Meson Production in Hadronic Z^0 Decays (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The inclusive production rates and differential cross-sections of photons and mesons with a final state containing photons have been measured with the OPAL detector at LEP. The light mesons covered...
Collaboration, The OPAL, Al, K. Ackerstaff Et
A search for stable and long-lived massive particles of electric charge |Q/e| = 1 or 2/3, pair-produced in e+e- collisions at centre-of-mass energies from 130 to 183 GeV, is reported by the OPAL...
An upper limit on the anomalous magnetic moment of the \tau lepton (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Using radiative Z^0 -> \tau^+ \tau^- \gamma events collected with the OPAL detector at LEP at \sqrt{s}= M_Z during 1990-95, a direct study of the electromagnetic current at the \tau\gamma vertex has...
A Search for Neutral Higgs Bosons in the MSSM and Models with Two Scalar Field Doublets (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
A search is described for the neutral Higgs bosons h^0 and A^0 predicted by models with two scalar field doublets and, in particular, the Minimal Supersymmetric Standard Model (MSSM). The search in...
Collaboration, The OPAL, Al, K. Ackerstaff Et
Events with four distinct jets from e^+e^- collisions, collected by the OPAL detector at centre-of-mass energies between 130 and 184 GeV, are analysed for a peak in the sum of dijet masses. This...
Production of f_0(980), f_2(1270) and \phi(1020) in hadronic Z^0 decay (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Inclusive production of the f_0(980), f_2(1270) and \phi(1020) resonances has been studied in a sample of 4.3 million hadronic Z^0 decays from the OPAL experiment at LEP. A coupled channel analysis...
Collaboration, The OPAL, Al, K. Ackerstaff Et
In e^+e^- collisions at centre-of-mass energies around 91 GeV, D^*0 mesons have been reconstructed using data collected with the OPAL detector at LEP. The hadronisation fraction has been measured to...
Search for charged Higgs bosons in e^+e- collisions at sqrt{s} = 130 - 172 GeV (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
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...
Measurements of the B^0_s and \Lambda_b Lifetimes (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
This paper presents updated measurements of the lifetimes of the B^0_s meson and the \Lambda_b baryon using 4.4 million hadronic Z^0 decays recorded by the OPAL detector at LEP from 1990 to 1995. A...
Measurement of the one-prong hadronic tau branching ratios at LEP (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The branching ratios of the \tau^- -> h^- \nu_\tau, \tau^- -> h^- \pi^0 \nu_\tau, \tau^- -> h^- >=2 \pi^0 \nu_\tau decays have been measured using the 1991-1995 data recorded with the OPAL detector...
Search for the B_c Meson in Hadronic Z^0 Decays (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
A search for decays of the B_c meson was performed using data collected from 1990-1995 with the OPAL detector on or near the Z peak at LEP. The decay channels B_c^+ -> J/psi pi^+, B_c^+ -> J/psi...
Collaboration, The OPAL, Al, K. Ackerstaff Et
Photonic events with large missing energy have been observed in e+e- collisions at centre-of-mass energies of 130, 136, 161 and 172 GeV using the OPAL detector at LEP. Results are presented based on...
Investigation of CP violation in B^0 -> J/psi K^0_S decays at LEP (1998)
Collaboration, The OPAL, Al, K. Ackerstaff Et
An investigation of CP violation was performed using a total of 24 candidates for B^0 -> J/psi K^0_S decay, with a purity of about 60%. These events were selected from 4.4 million hadronic Z^0 decays...
Collaboration, The OPAL, Al, K. Ackerstaff Et
Events containing a pair of charged leptons and significant missing transverse momentum are selected from a data sample corresponding to a total integrated luminosity of 20.6 pb^-1 at centre-of-mass...
Measurement of triple gauge boson couplings from W^+W^- production at sqrt{s} = 172 GeV (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
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...
Search for Unstable Heavy and Excited Leptons in e^+e^- Collisions at sqrt{s} = 170-172 GeV (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
We have searched for unstable neutral and charged heavy leptons, N and L^+/-, and for excited states of neutral and charged leptons, nu*, e*, mu* and tau*, in e^+e^- collisions at centre-of-mass...
Search for a Massive Di-photon Resonance at sqrt{s} = 91-172 GeV (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
A search for the resonant production of high mass photon pairs associated with a leptonic or hadronic system has been performed using a total data sample of 25.7 pb^-1 taken at centre-of-mass...
Collaboration, The OPAL, Al, K. Ackerstaff Et
This paper describes the measurement of the W boson mass, M_W, and decay width, Gamma_W, from the direct reconstruction of the invariant mass of its decay products in W pair events collected at a...
Multi-photon final states in e^+e^- collisions at sqrt{s} = 130-172 GeV (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The process e^+e^- -> gamma gamma (gamma) is studied using data recorded with the OPAL detector at LEP. The data sample corresponds to a total integrated luminosity of 25.38 pb^{-1} taken at...
Search for the Standard Model Higgs Boson in e^+e^- Collisions at sqrt{s} = 161-172 GeV (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
This paper describes a search for the Standard Model Higgs boson using data from e^+e^- collisions collected at center-of-mass energies of 161, 170 and 172 GeV by the OPAL detector at LEP. The data...
Asymmetry of Lambda Baryons in Hadronic Z^0 Decays (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The longitudinal polarization, the transverse polarization, and the forward-backward asymmetry of Lambda baryons have been measured using a sample of 4.34 million hadronic Z^0 decays collected with...
Measurement of the Photon Structure Function F_2^gamma at Low x (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Deep inelastic electron-photon scattering is studied using e+e- data collected by the OPAL detector at centre-of-mass energies sqrt{s_ee} ~ M_{Z^0}. The photon structure function F_2^gamma(x,Q^2) is...
Multiplicity distributions of gluon and quark jets and tests of QCD analytic predictions (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Gluon jets are identified in e+e- hadronic annihilation events by tagging two quark jets in the same hemisphere of an event. The gluon jet is defined inclusively as all the particles in the opposite...
Collaboration, The OPAL, Al, K. Ackerstaff Et
Production of events with hadronic and leptonic final states has been measured in e^+e^- collisions at centre-of-mass energies of 130-172 GeV, using the OPAL detector at LEP. Cross-sections and...
Search for Chargino and Neutralino Production at sqrt{s} = 170 and 172 GeV at LEP (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
A search for charginos and neutralinos, predicted by supersymmetric theories, has been performed using a data sample of 10.3 pb^-1 at centre-of-mass energies of sqrt(s) = 170 and 172 GeV with the...
Measurement of the Q^2 evolution of the photon structure function F_2^gamma (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
New measurements are presented of the photon structure function F_2^gamma(Q) at four values of Q^2 between 9 and 59 GeV/c^2 based on data collected with the OPAL detector at centre-of-mass energies...
Collaboration, The OPAL, Al, K. Ackerstaff Et
The inclusive production of prompt photons with energy above 10 GeV is measured using the OPAL detector in hadronic Z^0 decays at LEP. In contrast to previous measurements, the prompt photons were...
Measurement of f(c -> D^*+ X), f(b -> D^*+ X) and Gamma_cc(bar)/Gamma_had using D^*+/- Mesons (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
The production rates of D^*+/- mesons in charm and bottom events at centre-of-mass energies of about 91 GeV and the partial width of primary cc(bar) pairs in hadronic Z^0 decays have been measured at...
Spin alignment of leading K*(892)^0 mesons in hadronic Z^0 decays (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
Helicity density matrix elements for inclusive K*(892)^0 mesons from hadronic Z^0 decays have been measured over the full range of K^*0 momentum using data taken with the OPAL experiment at LEP. A...
A Measurement of the B_s^0 Lifetime using Reconstructed D_s^- Mesons (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
We report a measurement of the B^0_s meson lifetime from B_s^0 -> D^-_s X decays, where D_s^- mesons are reconstructed in the D_s^- -> phi pi^- and D_s^- -> K^{*0} K^- decay channels. From...
An upper limit on the branching ratio for tau decays into seven charged particles (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
We have searched for decays of the tau lepton into seven or more charged particles, using data collected with the OPAL detector from 1990 to 1995 in e^+e^- collisions at sqrt(s) ~ M_Z. No candidate...
Collaboration, The OPAL, Al, K. Ackerstaff Et
Using approximately 4.3 million hadronic Z^0 decays collected with the OPAL detector at LEP between 1990 and 1995, we measure the branching fractions of the Z^0 into up-type and down-type light...
An Updated Study of B Meson Oscillations using Dilepton Events (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
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...
A Study of B Meson Oscillations Using Hadronic Z^0 Decays Containing Leptons (1997)
Collaboration, The OPAL, Al, K. Ackerstaff Et
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...