Measurements of Z0Z^0 to Heavy-quark couplings at SLD

We present measurements of $Z^0$ to heavy-quark coupling electroweak parameters, $R_b$, $R_c$, and parity-violation parameter $A_c$, from SLD. The measurements are based on approximately 550k hadronic $Z^0$ events collected in 1993-98. Obtained preliminary results of $R_b$ and $R_c$ measurements are $R_b = 0.2159 \pm 0.0014 \pm 0.0014$ and $R_c = 0.1685 \pm 0.0047 \pm 0.0043$. In the $A_c$ measurement, we use four methods to determine the initial-quark charge: combined Kaon charge and Vertex charge, lepton, exclusively reconstructed D*, D-mesons, and a new method using inclusive soft-pion from D*. The preliminary results of these four methods were combined to give $A_c = 0.634 \pm 0.027$.Comment: 10 pages 5 figures Latex, Contribution to DPF '9

The scanning Compton polarimeter for the SLD experiment

For the 1994/95 run of the SLD experiment at SLAC, a Compton polarimeter measured the luminosity-weighted electron beam polarization to be (77.2 +- 0.5)%. This excellent accuracy is achieved by measuring the rate asymmetry of Compton-scattered electrons near the kinematic endpoint. The polarimeter takes data continuously while the electron and positron beams are in collision and achieves a statistical precision of better than 1% in a three minute run. To calibrate the polarimeter and demonstrate its accuracy, many scans are frequently done. These include scans of the laser polarization, the detector position with respect to the kinematic edge, and the laser power. Presented at the Workshop on High Energy Polarimeters at NIKHEF, Amsterdam, The Netherlands on September 9, 1996.Comment: 7 pages, 2 .eps figures, LATE

A preliminary measurement of the gluon splitting rate into bbˉb\bar{b} pairs in hadronic Z0Z^0 decays

We present a measurement of the rate of gluon splitting into bottom quarks, $g \to b\bar{b}$, in hadronic $Z^0$ decays collected by SLD from 1996 to 1998. The analysis was performed by looking for secondary bottom production in 4-jet events of any primary flavor. A topological vertex mass technique was used to tag the two jets with the smallest angle between them as $b/\bar{b}$. We obtained a rate of $g \to b\bar{b}$ per hadronic event to be $(3.07 \pm 0.71 {\rm (stat.)} \pm 0.66 {\rm (syst.)})\times 10^{-3}$ (preliminary).Comment: 11 pages 3 figures Latex, Contribution to DPF '9

Measurements of Parity-Violation Parameters at SLD

We present direct measurements of the parity-violation parameters $A_b$, $A_c$, and $A_s$ at the $Z^0$ resonance with the SLD detector. The measurements are based on approximately 530k hadronic $Z^0$ events collected in 1993-98. Obtained results are $A_b = 0.914\pm0.024$ (SLD combined: preliminary), $A_c = 0.635\pm0.027$ (SLD combined: preliminary), and $A_s = 0.895\pm0.066(stat.)\pm 0.062(sys.)$.Comment: 8 pages 2 figures Latex, Contribution to ICHEP200

B Decay Studies at SLD

We present three preliminary results from SLD on B decays: an inclusive search for the process b-> s gluon, a measurement of the branching ratio for the process B -> D D-bar X, and measurements of the charged and neutral B lifetimes. All three measurements make use of the excellent vertexing efficiency and resolution of the CCD Vertex Detector and the first two make use of the excellent particle identification capability of the Cherenkov Ring Imaging Detector. The b->sg analysis searches for an enhancement of high momentum charged kaons produced in B decays. Within the context of a simple, Jetset-inspired model of b->sg, a limit of BR(b->sg) < 7.6% is obtained. The B -> D D-bar X analysis reconstructs two secondary vertices and uses identified charged kaons to determine which of these came from charm decays. The result of the analysis is BR(B -> D D-bar X) = (16.2 +/- 1.9 +/- 4.2)%. The results of lifetime analysis are: \tau_{B^+} = 1.686 +/-0.025 +/- 0.042 ps, \tau_{B^0} = 1.589 +/- 0.026 +/- 0.055 ps and $\tau_{B^+}/\tau_{B^0} = 1.061 +/- ^{0.031}_{0.029} +/- 0.027.Comment: 12 Pages, 4 Figures. Contribution to DPF '9

Measurements of ALRA_{LR}, AleptonA_{lepton} and AbA_{b} from SLD

We present the measurements of the leptonic asymmetries in $Z^0$ decays measured by the SLD experiment at SLAC. A data sample of approximately 550,000 $Z^0$ bosons are used for the preliminary measurement of $A_{LR}(A_{e})$ and the leptonic final state measurements of $A_{e}$, $A_{\mu}$ and $A_{\tau}$, representing the entire set of 1992-1998 SLD runs. When combining all results, a preliminary value for the effective weak mixing angle is obtained: ${\sin}^2{\theta}_{W}^{eff} = 0.23109 \pm 0.00029$. We also present the direct measurements of $A_{b}$ from left-right forward-backward asymmetries, using partial data samples from 1993-1998 SLD runs. The preliminary value combines jet charge, cascade kaon and semileptonic decay analyses to obtain $A_{b} = 0.866 \pm 0.036$.Comment: 5 pages RevTex, 1 eps figure, Submitted to DPF99 Conference Proceedings, Parallel Sessions Talk 01-0

Preliminary Direct Measurement of the s-Quark Asymmetry

We present a preliminary direct measurement of the parity violating coupling of the Z boson to strange quarks, A_s, derived from a sample of approximately 300,000 hadronic decays of Z bosons produced with a polarized electron beam and recorded by the SLD experiment at SLAC between 1993 and 1997. Events with primary strange quarks are tagged by the presence in each event hemisphere of a high-momentum charged K meson, neutral K meson or Lambda hyperon identified using the Cherenkov Ring Imaging Detector and/or a mass tag. The CCD vertex detector is used to suppress the background from heavy flavor events. The strangeness of the tagged particle is used to sign the event thrust axis in the direction of the initial strange quark. The coupling A_s is obtained directly from a measurement of the left-right-forward-backward production asymmetry in polar angle of the tagged strange quark. To reduce the model dependence of the measurement, the background from primary up and down events is measured from the data, as is the analyzing power of the method for primary strange events. We measure A_s = 0.82+-0.10(stat.)+-0.08(syst.) (preliminary).Comment: 10 pages, 1 figur

E- SLD LIQUID ARGON CALORIMETER ERIC

The liquid argon calorimeter (LAC) of the SLD detector is a parallel plate- liquid argon sampling calorimeter, used to measure particle energies in Z ” decays at the Stanford Linear Collider. The LAC module design is based on a unique projective tower.structure, in which lead plates and segmented lead tiles serve both as absorb&amp;r%-‘and electrodes. The LAC front end electronics incorporates several novel features, including extensive multiplexing and optical fiber readout, which take advantage of the low SLC beam crossing frequency. The operational performance of the LAC during the recently completed SLD physics run (which recorded over 10000 Z ” events) is discussed

A TEST OF THE FLAVOR INDEPENDENCE OF STRONG INTERACTIONS *

We present a comparison of the strong couplings of b, c, and light (u, d, and s) quarks derived from multi-jet rates in flavor-tagged samples of hadronic Z 0 decays recorded with the SLC Large Detector at the SLAC Linear Collider. By comparing the rates of 3-jet events in these three samples we have extracted the Preliminary values of: α s (uds)/α s (all) = 0.96±0.03(stat.)±0.04(syst.)±0.02(theory), α s (c)/α s (all) = 1.16±0.11(stat.) ± 0.10(syst.)±0.07(theory), α s (b)/α s (all) = 0.98±0.04(stat.)±0.08(syst.)±0.02(theory). 1