355 research outputs found
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 Oscillations Using Exclusively Reconstructed Decays at SLD
We set a preliminary 95% C.L. exclusion on the oscillation frequency of
mixing using a sample of 400,000 hadronic decays
collected by the SLD experiment at the SLC during the 1996-98 run. In this
analysis, mesons are partially reconstructed by combining a fully
reconstructed with other decay tracks. The decays are
reconstructed via the and channels. The -hadron flavor at
production is determined by exploiting the large forward-backward asymmetry of
polarized decays as well as information from the hemisphere
opposite to the reconstructed B decay. The flavor of the at the decay
vertex is determined by the charge of the . A total of 361 candidates
passed the final event selection cuts. This analysis excludes the following
values of the mixing oscillation frequency: ps, ps, and ps 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
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
A preliminary measurement of the gluon splitting rate into pairs in hadronic decays
We present a measurement of the rate of gluon splitting into bottom quarks,
, in hadronic 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 . We
obtained a rate of per hadronic event to be (preliminary).Comment: 11 pages 3 figures Latex, Contribution to DPF '9
Combined results on b-hadron production rates and decay properties
Combined results on b-hadron lifetimes, b-hadron production rates, B^0_d -
\bar{B^0_d} and B^0_S - \bar{B^0_s} oscillations, the decay width difference
between the mass eigenstates of the B^0_s - \bar{B^0_s} system, the average
number of c and \bar{c} quarks in b-hadron decays, and searches for CP
violation in the B^0_d - \bar{B-0_d} system are presented. They have been
obtained from published and preliminary measurements available in Summer 2000
from the ALEPH, CDF, DELPHI, L3, OPAL and SLD Collaborations. These results
have been used to determine the parameters of the CKM unitarity triangle.Comment: Prepared from Contributions to the 2000 Summer conference
An Improved Direct Measurement of Leptonic Coupling Asymmetries with Polarized 's
We report new direct measurements of the -lepton coupling asymmetry
parameters , and , with polarized '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
, and . If lepton universality is assumed, a combined asymmetry parameter
results. This translates into an effective weak
mixing angle at the
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
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
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