Measurement of the b Quark Fragmentation Function in Z0 decay

We present preliminary results of a new measurement of the inclusive b quark fragmentation function in Z0 decays using a novel kinematic B hadron energy reconstruction technique. The measurement is performed using 150,000 hadronic Z0 events recorded in the SLD experiment at SLAC between 1996 and 1997. The small and stable SLC beam spot and the CCD-based vertex detector are used to reconstruct topological B-decay vertices with high efficiency and purity, and to provide precise measurements of the kinematic quantities used in this technique. We measure the B energy with good efficiency and resolution over the full kinematic range. We compare the measured scaled B hadron energy distribution with several functional forms of the B hadron energy distribution and predictions of several models of b quark fragmentation. Several functions are excluded by the data. The average scaled energy of the weakly decaying B hadron is measured to be xB = 0.714 +/- 0.005 (stat) +/- 0.007 (syst) +/- 0.002 (model) (preliminary).Comment: 31 pages, 11 figures, EPS99, Lepton-Photon 9

Time Dependent Bs0−Bs0ˉB_s^0 - \bar{B_s^0} Oscillations Using Exclusively Reconstructed Ds+D_s^+ Decays at SLD

We set a preliminary 95% C.L. exclusion on the oscillation frequency of $B_s^0 - \bar{B_s^0}$ mixing using a sample of 400,000 hadronic $Z^0$ decays collected by the SLD experiment at the SLC during the 1996-98 run. In this analysis, $B_s^0$ mesons are partially reconstructed by combining a fully reconstructed $D_s$ with other $B_s^0$ decay tracks. The $D_s$ decays are reconstructed via the $\phi \pi$ and $K^* K$ channels. The $b$-hadron flavor at production is determined by exploiting the large forward-backward asymmetry of polarized $Z^0 \to b \bar{b}$ decays as well as information from the hemisphere opposite to the reconstructed B decay. The flavor of the $B_s^0$ at the decay vertex is determined by the charge of the $D_s$. A total of 361 candidates passed the final event selection cuts. This analysis excludes the following values of the $B_s^0 - \bar{B_s^0}$ mixing oscillation frequency: $\Delta m_s < 1.5$ ps$^{-1}$, $2.6 < \Delta m_s < 4.9$ ps$^{-1}$, and $10.8 < \Delta m_s < 13.5$ ps$^{-1}$ at the 95% confidence level.Comment: 24 pages, 9 figures, contributed to the XXX International Conference on High Energy Physics (ICHEP 2000), Osaka, Japan, 27 July - 2 August, 200

Symmetry Tests in Polarized Z0 Decays to bbg

Angular asymmetries have been measured in polarized Z0 decays to bbg collected by the SLD experiment at the SLC. A high purity bbg event sample is selected by utilizing B lifetime information given by the SLD CCD pixel vertex detector and the stable micron-size SLC beams, and the b- and bbar-jets are identified using lifetime information and momentum-weighted track charge. The forward-backward asymmetry is observed in the b-quark polar angle distribution, and the parity-violation parameter is measured to test the Standard Model. Two angular correlations between the three-jet plane and the Z0 polarization are studied. The CP-even and T-odd, and the CP-odd and T-odd, angular asymmetries are sensitive to physics beyond the Standard Model. The latter requires tagging both the b- and bbar-jet. We measure the expectation values of these quantities to be consistent with zero and set limits on the correlations at the 5% level.Comment: 20 pages, 5 figure

Production of Charged pi, K and p in Hadronic Z0 Decays

We have updated our results on identified charged hadron production using the full SLD data sample of 550,000 hadronic Z^0 decays taken between 1993 and 1998. The SLD Cherenkov Ring Imaging Detector allows the identification of clean samples of charged pions, kaons and protons over a wide momentum range, providing precise tests of perturbative QCD calculations and of fragmentation models. We have studied flavor-inclusive Z^0 decays, as well as decays into light, c and b flavors, selected using the SLD vertex detector. In addition we have updated our comparison of hadron and antihadron production in light quark (rather than antiquark) jets, selected using the high SLC electron beam polarization. Differences between hadron and antihadron production at high momentum fraction provide precise measurements of leading particle production and new, stringent tests of fragmentation models.Comment: 22 pages, 8 figures; paper contributed to eps-hep99 and lp9

Measurement of the B+ and B0 Lifetimes using Topological Vertexing at SLD

The lifetimes of B+ and B0 mesons have been measured using the entire sample of 550,000 hadronic Z0 decays collected by the SLD experiment at the SLC between 1993 and 1998. In this paper, we describe the inclusive analysis of the 350,000 hadronic Z0 decays collected in 1997-98 with the upgraded SLD vertex detector. In this data period, a high statistics sample of 30903 (20731) charged (neutral) vertices with good charge purity is obtained. The charge purity is enhanced by using the vertex mass, the SLC electron beam polarization (73% for 1997-8) and an opposite hemisphere jet charge technique. Combining the results of this data sample with the results from the earlier data yield the following preliminary values: $\tau_{B^+}=1.623\pm0.020($stat$)\pm0.034$(syst) ps, $\tau_{B^0}=1.589\pm0.021($stat$)\pm0.043$(syst) ps, $\tau_{B^+}/\tau_{B^0} = 1.037\pm^{0.025}_{0.024}($stat$) \pm0.024$(syst).Comment: 19 pages, 4 figures, submitted to EPS99 and Lepton-Photon 9

A Study of Correlations between Identified Charged Hadrons in Hadronic Z^0 Decays

We present a preliminary study of correlations in rapidity between pairs of identified charged pions, kaons and protons using the entire SLD data sample of 550,000 hadronic Z^0 decays. Short range charge correlations are observed between all combinations of these hadron species, indicating local conservation of quantum numbers and charge ordering in the jet fragmentation process. The rapidity range of this effect is found to be independent of particle momentum. A strong long-range K^+K^- correlation is observed at high-momentum and weaker long-range pi^+pi^-, pi^+K^-, pK^- and pp-bar correlations are observed in light flavor events, providing new information on leading particle production in u, d and s jets. The long-range correlations observed in c-cbar and bb-bar events are markedly different and consistent with expectations based on known decay properties of the leading heavy hadrons. In addition, the SLC electron beam polarization is used to tag the quark hemisphere in each event, allowing the first study of rapidities signed such that positive rapidity is along the quark rather than antiquark direction. Distributions of ordered differences in signed rapidity between pairs of particles provide a direct probe of quantum number ordering along the quark-antiquark axis and other new insights into the fragmentation process.Comment: 28 pages, 12 figures; paper contributed to EPS-HEP99 and LP9

Measurement of AcA_c with charmed mesons at SLD

We present a direct measurement of the parity-violation parameter A_c. The measurement is based on 550k Z^0 decays collected by the SLD detector. The mean electron-beam polarization is |P_e| = 73 %. The tagging of c-quark events was performed using two methods: The exclusive reconstruction of D^*+, D^+, and D^0 mesons, and the inclusive P_T spectrum of soft-pions (pi_s) in the decay of D^*+ -> D^0 pi_s^+. The results of these two methods are combined to give A_c = 0.688 +- 0.035(stat.) +- 0.025(sys.) (preliminary).Comment: 12 pages 4 figures Latex. Contributed to EPS99 and to Lepton-Photon9

Determination of Electroweak Parameters at the SLC

We present an improved measurement of the left-right cross section asymmetry Alr for Z boson production by e+e- collisions. The measurement was performed at a center-of-mass energy of 91.28 GeV with the SLD detector at the SLAC Linear Collider (SLC) during the 1994-95 running period. The luminosity-weighted average polarization of the SLC electron beam during this run was measured to be (77.23 +/- 0.52)%. Using a sample of 93,644 hadronic Z decays, we measure the pole asymmetry Alr0 to be 0.1512 +/- 0.0042(stat.) +/- 0.0011(syst.) which is equivalent to an effective weak mixing angle of 0.23100 +/- 0.00054(stat.) +/- 0.00014(syst.). We also present a preliminary direct measurement of the Z-lepton coupling asymmetries A_e,A_mu, and A_tau extracted from the differential cross section observed in leptonic Z decays. We combine these results with our previous Alr measurement to obtain a combined determination of the weak mixing angle of 0.23061 +/- 0.00047.Comment: Presented at the 28th International Conference on High Energy Physics, Warsaw, Poland, July 25-31, 1996. 16 Pages, LaTe

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

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