arXiv subjects

SLD Collaboration

Publications and source records attributed to SLD Collaboration.

At least 19 recordsLinked to original sources

arXiv2010

Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results obtained at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D\O\ at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, M{\o}ller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2009 are new combinations of results on the width of the W boson and the mass of the top quark.

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arXiv2009

Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D{\O}at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, M{\o}ller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2008 are new combinations of results on the W-boson mass and the mass of the top quark.

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arXiv2008

Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D{\O}at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, M{\o}ller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2007 are new combinations of results on the W-boson mass and width and the mass of the top quark.

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arXiv2005

Measurement of the branching ratios of the Z0 into heavy quarks

We measure the hadronic branching ratios of the Z0 boson into heavy quarks: Rb=Gamma(Z0->bb)/Gamma(Z0->hadrons) and Rc=Gamma(Z0->cc/Gamma(Z0->hadrons) using a multi-tag technique. The measurement was performed using about 400,000 hadronic Z0 events recorded in the SLD experiment at SLAC between 1996 and 1998. The small and stable SLC beam spot and the CCD-based vertex detector were used to reconstruct bottom and charm hadron decay vertices with high efficiency and purity, which enables us to measure most efficiencies from data. We obtain, Rb=0.21604 +- 0.00098(stat.) +- 0.00073(syst.) -+ 0.00012(Rc) and, Rc= 0.1744 +- 0.0031(stat.) +- 0.0020(syst.) -+ 0.0006(Rb)

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arXiv2005

Direct Measurements of A_b and A_c using Vertex/Kaon Charge Tags at SLD

Exploiting the manipulation of the SLC electron-beam polarization, we present precise direct measurements of the parity violation parameters A_c and A_b in the Z boson - c quark and Z boson - b quark coupling. Quark/antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLD CCD vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-98 sample of 400,000 Z decays, produced with an average beam polarization of 73.4%, we find A_c = 0.673 +/- 0.029 (stat.) +/- 0.023 (syst.) and A_b = 0.919 +/- 0.018 (stat.) +/- 0.017 (syst.).

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arXiv2003

First measurement of the double-inclusive B/Bbar hadron energy distribution in e+e- annihilations, and of angle-dependent moments of the B and Bbar energies

We have made the first measurement of the double-inclusive B/Bbar energy distribution in e+e- annihilations, using a sample of 400,000 hadronic Z0 decay events recorded in the SLD experiment at SLAC between 1996 and 1998. The small and stable SLC beam spot and the CCD-based vertex detector were used to reconstruct B/Bbar decay vertices with high efficiency and purity, and to provide measurements of the kinematic quantities used to calculate the B energies in this novel technique. We measured the B/Bbar energies with good efficiency and resolution over the full kinematic range. We measured moments of the scaled energies of the B and Bbar hadrons vs. the opening angle between them. By comparing these results with perturbative QCD predictions we tested the ansatz of factorisation in heavy-quark production. A recent next-to-leading order calculation reproduces the data.

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arXiv2003

Improved Direct Measurement of the Parity-Violation Parameter A_b Using a Mass Tag and Momentum-Weighted Track Charge

We present an improved direct measurement of the parity-violation parameter A_b in the Z boson-b quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z -> b b-bar events via the topological reconstruction of the B hadron mass. Manipulation of the SLC electron-beam polarization permits the measurement of A_b to be made independently of other Z-pole coupling parameters. From the 1996-98 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A_b = 0.906 +/- 0.022(stat.) +/- 0.023(syst.).

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arXiv2002

A Search for Time-Dependent B0s-B0sbar Oscillations Using Exclusively Reconstructed Ds+/- Mesons

A search for Bs0-Bs0bar oscillations is performed using a sample of 400,000 hadronic Z0 decays collected by the SLD experiment. The Bs0 candidates are reconstructed in the Bs0 to Ds-,X channel with Ds- to phi,pi- or K*0K-. The Bs0 production flavor is determined using the large forward-backward asymmetry of polarized Z0 to b,bbar decays and charge information in the hemisphere opposite that of the Bs0 candidate. The decay flavor is tagged by the charge of the Ds+/-. From a sample of 361 candidates with an average Bs0 purity of 40%, we exclude the following values of the oscillation frequency: Delta m_s < 1.4 ps^{-1} and 2.4 < Delta m_s < 5.3 ps^{-1} at the 95% confidence level.

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arXiv2002

Improved Direct Measurement of $A_b$ and $A_c$ at the $Z^0$ Pole Using a Lepton Tag

The parity violation parameters $A_b$ and $A_c$ of the $Zb{\bar b}$ and $Zc\bar{c}$ couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the $Z^0$ pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-98 SLD sample of 550,000 $Z^0$ decays produced with highly polarized electron beams we measure $ A_b = 0.919 \pm 0.030_{stat} \pm 0.024_{syst} $, and $ A_c = 0.583 \pm 0.055_{stat} \pm 0.055_{syst} $.

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arXiv2000

Time Dependent $B_s^0 - \bar{B_s^0}$ Oscillations Using Exclusively Reconstructed $D_s^+$ 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.

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arXiv2000

A High-Precision Measurement of the Left-Right Z Boson Cross-Section Asymmetry

We present a measurement of the left-right cross-section asymmetry (ALR) for Z boson production by e+e- collisions. The measurement includes the final data taken with the SLD detector at the SLAC Linear Collider (SLC) during the period 1996-1998. Using a sample of 383,487 Z decays collected during the 1996-1998 runs we measure the pole-value of the asymmetry, ALR0, to be 0.15056+-0.00239 which is equivalent to an effective weak mixing angle of sin2th(eff) = 0.23107+-0.00030. Our result for the complete 1992-1998 dataset comprising 537 thousand Z decays is sin2th(eff) = 0.23097+-0.00027.

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arXiv1999

Search for Charmless Hadronic Decays of B Mesons with the SLD Detector

Based on a sample of approximately 500,000 hadronic Z0 decays accumulated between 1993 and 1998, the SLD experiment has set limits on 24 fully charged two-body and quasi two-body exclusive charmless hadronic decays of B+, B0, and B0_s mesons. The precise tracking capabilities of the SLD detector provided for the efficient reduction of combinatoric backgrounds, yielding the most precise available limits for ten of these modes.

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arXiv1999

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.

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arXiv1999

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).

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arXiv1999

An Improved Measurement of the b Quark Fragmentation Function in Z0 Decays

We present a new preliminary measurement of the 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 scaled B hadron energy distribution with several functional forms of the B hadron energy distribution and models of b quark fragmentation. Several functions including JETSET + Peterson are excluded by the data. The average scaled energy of the weakly decaying B hadron is measured to be XB = 0.719 +/- 0.005 (stat) +/- 0.007 (syst) +/- 0.001 (model) (preliminary).

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arXiv1997

A Measurement of Rb using a Vertex Mass Tag

We report a new measurement of Rb = Gamma(Z0->b-bbar) / Gamma(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 130k hadronic Z0 events, collected with the SLD at the SLC. The method utilizes the 3-D 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 Rb=0.2142+/-0.0034(stat.)+/-0.0015(syst.)+/-0.0002(R_c).

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arXiv1997

Measurement of the Tau Neutrino Helicity and the Michel Parameters in Polarized e+e- Collisions

We present a new measurement of the tau neutrino helicity, hnu and the tau Michel parameters rho, eta, xi and the product delta xi. The analysis exploits the highly polarized SLC electron beam to extract these quantities directly from a measurement of the tau decay spectra, using the 1993-1995 SLD data sample of 4328 e+e- --> Z0 --> tau+tau- events. From the decays tau --> pi nu(tau) and tau --> rho nu(tau) we obtain a combined value hnu=-0.93+/-0.10+/-0.04. The leptonic decay channels yield combined values of rho=0.72+/-0.09+/-0.03, xi=1.05+/-0.35+/-0.04 and delta xi=0.88+/-0.27+/-0.04.

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arXiv1996

An Improved Measurement of the Left-Right Z0 Cross Section Asymmetry

We present a new 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). The luminosity-weighted average polarization of the SLC electron beam was (77.23+-0.52)%. Using a sample of 93,644 Z decays, we measure the pole-value of the asymmetry, ALR0, to be 0.1512+-0.0042(stat.)+-0.0011(syst.) which is equivalent to an effective weak mixing angle of sin**2(theta_eff)=0.23100+-0.00054(stat.)+-0.00014(syst.).

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