1,721,041 research outputs found
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VXD3: The SLD vertex detector upgrade based on a 307 Mpixel CCD system
Get PDFThe SLD Collaboration is building a new CCD vertex detector (VXD3) comprising 96 3.2 Mpixel CCDs of 13 cm{sup 2} each for a total of 307 million pixels. This system is an upgrade of the Pioneering CCD vertex detector VXD2 which has operated in SLD since 1992. The CCDs of VXD3 are mounted on beryllium ladders in three cylinders, providing three space point measurements along each track of about 5 microns resolution in all three coordinates. The design and construction of VXD3 builds on three years of successful performance of VXD2. Significant improvements are achieved with VXD3 in impact parameters resolution (about a factor of two) and acceptance ({approximately}20%) through optimized geometry and reduced material. New readout electronics have been developed for this system. This new vertex detector will be installed in late 1995 for the future runs of SLD
SLAC-PUB-7585 August 13, 1997 A Preliminary Measurement of R b using the Upgrade SLD Vertex Detector
No full textWe report a new measurement of R b using data obtained during the 1996 SLD run. This measurement uses a double tag technique, where the selection of a b hemisphere is based on the reconstructed mass of the B hadron decay vertex. The method utilizes the 3D vertexing capabilities of SLD's new CCD vertex detector and the small and stable SLC beams to obtain a high b tagging efficiency and purity of 47:9% and 97:6%, respectively. We obtain a preliminary result of R b = 0:2101 \Sigma 0:0034 stat: \Sigma 0:0022 syst: \Sigma 0:0003 Rc for 1996 data. With our previous measurement from 1993-95 data, we obtain a combined preliminary 93-96 result of R b = 0:2124 \Sigma 0:0024 stat: \Sigma 0:0017 syst: . Submitted to the International Europhysics Conference on High Energy Physics (HEP97), 19-26 August 1997, Jerusalem, Israel.
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Preliminary measurement of leading particle effects in hadronic Z{sup 0} decays
No full textWe present preliminary evidence for leading particle production in hadronic decays of the Z{sup 0} to light quark pairs using 150,000 events recorded in the SLD experiment at SLAC. The highly polarized electron beam produced by the SLC is used to tag quark and antiquark jets, and a signed impact parameter technique is employed to reject heavy flavor events. Charged hadrons are identified in the SLD Cherenkov Ring Imaging Detector (CRID) and {Lambda}/{bar {Lambda}} are reconstructed using their charged decay modes. In a high purity sample of quark jets, the baryon momentum spectrum is harder that that of the antibaryon, and conversely for a sample of antiquark jets, supporting the hypothesis that the faster particles in jets are more likely to carry the primary quark or antiquark from the Z{sup 0} decay. Similarly, more high momentum K{sup -} that K{sup +} are observed in quark jets and conversely for antiquark jets, consistent with the hypothesis that leading K{sup {+-}} are produced predominantly in s{bar s} events rather than {ital u}{bar {ital u}} events
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A preliminary measurement of the b quark fragmentation function in hadronic Z{sup 0} decays
Get PDFWe present a measurement of the {ital b} quark fragmentation function from a sample of semi-leptonic {bold B} decays collected between 1993 and 1995 in the SLD experiment at SLAC. The energy of each tagged {bold B} hadron was reconstructed using information from the lepton and a partially reconstructed charm decay vertex. A comparison of the scaled energy distribution with several phenomenological models of heavy quark fragmentation was made, using the same model in each case to correct the data. The average scaled energy was found to be {l_angle}{chi}{sub E}{r_angle} = 0.697{+-}0.012({ital stat}){sup +0. 028}{sub -0.024} ({ital syst})(preliminary)
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Measurement of the charged multiplicities of b, c and light quark events from Z{sup 0} decays
No full textAverage charged multiplicities have been measured separately for {ital b, c} and light quark ({ital u, d, s}) events from Z{sup 0} decays at SLD. Impact parameters of charged tracks were used to select enriched samples of {ital b} and light quark events. We measured the charged multiplicities: {bar {ital n}}{sub {ital uds}} = 19.80 {+-} 0.09 ({ital stat}) {+-} 0.57 ({ital syst}), {bar {ital n}}{sub {ital c}} = 21.17 {+-} 0.44 ({ital stat}) {+-} 1.01 ({ital syst}) and {bar {ital n}}{sub {ital b}}{+-}23.14 {+-} 0.09 ({ital stat}) {+-} 1.03 ({ital syst}) (PRELIMINARY), from which we derived the differences between the total average charged multiplicities of {ital c} or {ital b} quark events and light quark events: {delta}{bar {ital n}}{sub {ital c}} = 1.37 {+-} 0.45 ({ital stat}) {+-} 0.86 ({ital syst}) and {delta}{bar {ital n}}{sub {ital b}} = 3.34 {+-} 0. 13 ({ital stat}) {+-} 0.77 ({ital syst}) (PRELIMINARY). We compared these measurements with those at lower center-of-mass energies and with QCD predictions
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Measurement of the polarized forward-backward asymmetry of Z{sup 0} {yields} b{bar b} using a lifetime tag and momentum-weighted track charge
No full textWe present a direct measurement of the parity-violating parameter A{sub b} by analyzing the left-right forward-backward asymmetry of b quarks in e{sup +}e{sup {minus}} {yields} Z{sup o} {yields} b{bar b}. The SLD experiment observes hadronic decays of Z{sup o} bosons produced at resonance in collisions of longitudinally polarized electrons and unpolarized positrons at the SLC. Heavy flavor decays of the Z{sup o} are identified by taking advantage of the long lifetime of B hadrons, the small, stable SLC beam spot, and precise tracking from SLD. The asymmetry A{sub b} is measured with a self-calibrating technique employing momentum-weighted track charge from both hemispheres in the tagged events. From our 1994--1995 sample of 3.6 pb{sup {minus}1} of e{sup +}e{sup {minus}} annihilation data with a luminosity-weighted average e{sup {minus}} polarization of 77.3%, and our 1993 sample of 1.8 pb{sup {minus}1} with a luminosity-weighted polarization of 63.1%, we obtain A{sub b}(preliminary) = 0.843 {plus_minus} 0.046(stat.) {plus_minus} 0.051(syst.)
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Factorial and cumulant moments in e{sup +}e{sup {minus}} {yields} hadrons at the Z{sup 0} resonance
No full textThe ratio of cumulant to factorial moments of the charged particle multiplicity distribution in hadronic Z{sup 0} decays has been measured in the SLD experiment at SLAC. The data were corrected for effects introduced by the detector. We find that this ratio, as a function of the moment rank q, decreases sharply to a negative minimum at q{approx}5, followed by a sequence of quasi-oscillations. We show that the truncation of the tail of the multiplicity distribution due to finite statistics only has a small effect on this result. The observed features are in qualitative agreement with expectations from higher order perturbative QCD
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Preliminary measurements of production of {pi}{sup {plus_minus}}, K{sup {plus_minus}}, p, K{sup 0} and {Lambda}{sup 0} in hadronic Z{sup 0} decays
No full textWe have measured production of {pi}{sup {+-}}, {Kappa}{sup {+-}}, {ital p}/{ital {bar p}}, {Kappa}{sup 0} and {Lambda}{sup 0}/{bar {Lambda}}{sup 0} as a function of momentum in inclusive hadronic {ital Z}{sup 0} decay events and separately in events containing primary light-({ital uds}) and {ital b}-quarks. The SLD Cherenkov Ring Imaging Detector was used to identify charged pions, kaons, and protons over most of the available momentum range 0.8{lt}{ital p}{lt}33 GeV/c. The neutral {Kappa}{sup 0}{sub s} and {Lambda}{sup 0} were reconstructed using the {pi}{sup +}{pi}{sup -} and {ital p}{pi}{sup -} decay modes, respectively. We present the first comparisons of momentum of charged tracks measured in the SLD Vertex Detector. Substantial differences are observed, consistent with the kinematics of {ital B}-hadron production in Z{sup 0} decays and the properties of {ital B}-hadron decays as measured at lower energies
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A study of the orientation and energy partition of three-jet events in hadronic Z{sup 0} decays
No full textUsing hadronic Z{sup 0} decays collected in the SLD experiment at SLAC we have measured the distributions of the jet energies in e{sup +}e{sup -}{yields} Z{sup 0}{yields} three-jet events of the three orientation angles of the event plane. We find that these distributions are well described by perturbative QCD incorporating vector gluons. We have also compared our data with models of scalar and tensor gluon production, and discuss limits on the relative contributions of these particles to three-jet production in e{sup +}e{sup -} annihilation
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A study of rapidity gaps in e{sup +}e{sup {minus}} {yields} Z{sup 0} events
No full textDistributions of rapidity gaps between charged particles are studied in Z{sup 0} decay events recorded by the SLD experiment at SLAC. We find that our measured gap spectra are well modeled by standard Monte Carlo simulations of hadronisation. Gaps in hadronic events are studied as a function of event primary flavor, jet multiplicity and total charged multiplicity
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