[en] This experiment was performed with the SLD detector at the Stanford Linear Accelerator Center. Only charged tracks measured in the central drift chamber were used for the measurement of the jet production rates. The value of the strong coupling α_s(M_Z^o) is determined from the production rates of jets in hadronic Z⁰ decays in e⁺ e^- annihilations. The relative jet rates are obtained using the JADE-type algorithms. The results are compared with the jet rates obtained from a new jet algorithm proposed by N. Brown et al. called the ''Durham'' algorithm. The data can be well described by O(α_s²) QCD calculations and by QCD shower model calculations. A fit of the theoretical predictions to the data taken with the SLD yields a value, α_s(M_Z^o) = 0.120 ± 0.002(stat.) ± 0.003(exp.)_-0.009^+0.011(theor.). The error is dominated by the theoretical uncertainties. The measurement is compared with results from other experiments and it is shown that the value obtained for α_s agrees well with these results and furthermore supports the evidence for the running of the strong coupling, consistent with the non-Abelian nature of QCD. The Stanford Linear Collider (SLC) can deliver partially longitudinally polarized electrons to the interaction point. Jet production rates and values for α_s are calculated both for right-handed and left-handed initial state electrons. All results are consistent with the unpolarized result, as predicted by the Standard Model

[en] This experiment was performed with the SLD detector at the Stanford Linear Accelerator Center. Only charged tracks measured in the central drift chamber were used for the measurement of the jet production rates. The value of the strong coupling α_s(M_Z⁰) is determined from the production rates of jets in hadronic Z⁰ decays in e⁺e^- annihilations. The relative jet rates are obtained using the JADE-type algorithms. The results are compared with the jet rates obtained from a new jet algorithm proposed by N. Brown et al. called the open-quotes Durhamclose quotes algorithm. The data can be well described by O (α²_s) QCD calculations and by QCD shower model calculations. A fit of the theoretical predictions to the data taken with the SLD yields a value α_s(M_Z⁰) = 0.120 ± 0.002(stat)±0.003(exp.)^+0.011_-0.009(theor.). The error is dominated by the theoretical uncertainties. The measurement is compared with results from other experiments and its is shown that the value obtained for α_s agrees well with these results and furthermore supports the evidence for the running of the strong coupling, consistent with the non-Abelian nature of QCD. The Stanford Linear Collider (SLC) can deliver partially longitudinally polarized electrons to the interaction point. Jet production rates and values for α_s are calculated both for right-handed and left-handed initial state electrons. All results are consistent with the unpolarized result, as predicted by the Standard Model

[en] We present jet rates in hadronic decays of Z⁰ bosons measured by the SLD experiment at SLAC. The data are analyzed in terms of the JADE and recently proposed Durham algorithms, and are found to be in agreement with the predictions of perturbative QCD plus fragmentation Monte Carlo models of hadron production. Corrected 2, 3 and 4-jet rates are well described by ο(α_s²) perturbative QCD calculations. From fits to the differential 2-jet distribution the strong coupling α_s(M_Z) is measured to be α_s(M_Z) = 0.119 ± 0.002(stat.) ± 0.003(exp.syst.) ± 0.014(theory) (preliminary). The largest contribution to the error arises from the theoretical uncertainty in choosing the QCD renormalisation scale

[en] We describe here a proposal for a light injection calibration system for the MINOS detectors based on ultra bright blue LEDs as the light source. We have shown that these LEDs are bright enough to span over two orders of magnitude in light intensity, commensurate with that expected in a single scintillator strip in the MINOS neutrino detectors

[en] The radiation damage to Si PIN diodes such as used in the OPAL SiW luminometer was studied. It was found that the increase in leakage current after exposure to bursts of 500 MeV electrons is >0.2 x 10³ times higher than after the exposure of an equivalent dose of electrons emitted from a Strontium β source. Highly-energetic electrons produce a similar amount of damage to silicon as do protons or neutrons. (orig.)

[en] The radiation monitoring and beam dump system of the OPAL silicon microvertex detector is described. This system was designed and implemented to measure the radiation dose over time scales varying from a millisecond to a year, and to induce a fast beam dump if the radiation exceeds a given threshold in dose and in dose rate within a very small time interval. The system uses reverse-biased silicon diodes as sensitive elements and good stability is achieved by AC coupling of the amplifiers to the sensors. (orig.)

[en] We present direct measurements of the Z⁰ -lepton coupling asymmetry parameters A_e , A_μ , and A_τ , based on a data sample of 12063leptonic Z⁰ decays collected by the SLD detector. The Z bosons are produced in collisions of beams of polarized e^- with unpolarized e⁺ at the SLAC Linear Collider. The couplings are extracted from the measurement of the left-right and forward-backward asymmetries for each lepton species. The results are A_e=0.152±0.012(stat) ±0.001(syst) , A_μ=0.102±0.034±0.002 , and A_τ=0.195±0.034±0.003 . copyright 1997 The American Physical Society

[en] We present a new measurement of the τ neutrino helicity h_ντ and the τ Michel parameters ρ , η , ξ , and the product δξ . The analysis exploits the highly polarized SLC electron beam to extract these quantities directly from a measurement of the τ decay spectra, using the 1993 endash 1995 SLD data sample of 4328 e⁺e^-→Z⁰→τ⁺τ^- events. From the decays τ→πν_τ and τ→ρν_τ we obtain a combined value h_ντ=-0.93±0.10± 0.04 . The leptonic decay channels yield combined values of ρ=0.72±0.09±0.03 , ξ=1.05±0.35±0.04 , and δξ=0.88±0.27±0.04 . copyright 1997 The American Physical Society

[en] We report a new measurement of R_b=Γ_Z⁰→bbarb /Γ_{Z⁰→hadrons} using a double tag technique, where the b hemisphere selection is based on the reconstructed mass of the B hadron decay vertex. The measurement was performed using a sample of 130x10³ hadronic Z⁰ events, collected with the SLD detector at SLC. The method utilizes the 3D vertexing abilities of the CCD pixel vertex detector and the small stable SLC beams to obtain a high b -tagging efficiency and purity. We obtain R_b=0.2142±0.0034(stat) ±0.0015(syst)±0.0002( R_c) . copyright 1998 The American Physical Society

[en] The lifetimes of B⁺ and B⁰ mesons are measured using a sample of 150000hadronic Z⁰ decays collected by the SLD experiment at the SLAC Linear Collider between 1993 and 1995. Two analyses are presented in which the decay length and charge of the B meson are reconstructed. The first method uses a novel topological vertexing technique while the second uses semi-inclusively reconstructed semileptonic decays. The topological analysis yields a sample of 6033 (3665) charged (neutral) vertices with good charge purity, whereas the semileptonic analysis yields a smaller sample of 634 (584) charged (neutral) decays with excellent charge purity. Combining the results from both analyses, we find τ_B⁺=1.66±0.06(stat )±0.05(syst) ps, τ_B⁰=1.64±0.08(stat )±0.08(syst) ps, and τ_B⁺/τ_B⁰ =1.01±0.07(stat)±0.06( syst) . copyright 1997 The American Physical Society