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

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

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

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

Measurement of Rb at SLD

We report a new measurement of Rb=Gamma(Z -> bb)/ Gamma(Z -> hadrons) using a double tag technique where the b selection is based on topological reconstruction of the mass of the B-decay vertex. The measurement was performed using a sample of 150k hadronic Z0 events collected with the SLD at the SLAC Linear Collider during the years 1993-1995. The method utilizes the 3-D vertexing abilities of the SLD CCD pixel vertex detector and the small stable SLC beams to obtain a high b tagging efficiency of 37% for a purity of 97.2%. The high purity reduces the systematics introduced by charm contamination and correlations with Rc. We obtain a result of Rb=0.2176+/-0.0033(stat.)+/-0.0017(syst.)+/-0.0008(Rc). (Presented at the XXXIst Rencontres de Moriond Electroweak Interactions and Unified Theories, Les Arcs, Savoie, France, March 16-23, 1996.)Comment: 12 pages, LaTeX, 3 eps figures, all in tar gzipped fil

An Improved Direct Measurement of Leptonic Coupling Asymmetries with Polarized Z0Z^0's

We report new direct measurements of the $Z^0$-lepton coupling asymmetry parameters $A_e$, $A_{\mu}$ and $A_{\tau}$, with polarized $Z^0$'s collected by the SLD detector at the SLAC Linear Collider. The parameters are extracted from the measurement of the left-right-forward-backward asymmetries for each lepton species. The 1996, 1997 and 1998 SLD runs are included in this analysis and combined with published data from the 1993-95 runs. Preliminary results are $A_e = 0.1558 \pm 0.0064$, $A_{\mu}=0.137 \pm 0.016$ and $A_{\tau}=0.142 \pm 0.016$. If lepton universality is assumed, a combined asymmetry parameter $A_{l} = 0.1523 \pm 0.0057$ results. This translates into an effective weak mixing angle $\sin^2\theta^{eff}_W = 0.23085 \pm 0.00073$ at the $Z^0$ resonance.Comment: 18 pages, 1 figure, Latex. Paper contributed to Lepton-Photon Symposium 199

Direct Measurement of A_b using Charged Kaons at the SLD Detector

We report a new measurement of A_b using data obtained by SLD in 1997-98. This measurement uses a vertex tag technique, where the selection of a b hemisphere is based on the reconstructed mass of the bottom hadron decay vertex. The method uses the 3D vertexing capabilities of SLD's CCD vertex detector and the small and stable SLC beams to obtain a high b-event tagging efficiency and purity of 78% and 97%, respectively. Charged kaons identified by the CRID detector provide an efficient quark-antiquark tag, with the analyzing power calibrated from the data. We obtain a preliminary result of A_b = 0.997 \pm 0.044 \pm 0.067Comment: 10 pages, 2 figures. Paper contributed to EPS-HEP 99 and Lepton-Photon Symposium 199

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

Tau Physics with Polarized Beams

We present the first results on tau physics using polarized beams. These include measurements of the $\tau$ Michel parameters $\xi$ and $\xi\delta$ and the $\tau$ neutrino helicity $h_\nu$. The measurements were performed using the SLD detector at the Stanford Linear Collider (SLC). (Invited talk at the 1995 International Europhysics Conference on High Energy Physics, Brussels, Belgium, July 27 - August 2, 1995.)Comment: 7 pages, uuencoded gzip-compressed postscript (83 kB) Uncompressed postscript file (855 kB) available via anonymous ftp as ftp://ftp.slac.stanford.edu/users/daoudi/sldtaupb.p