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Z{sup 0} pole direct measurements of the parity violation parameters A{sub b} and A{sub c} at SLD

Description: This report presents three different techniques used at SLD to measure directly the parity violation parameters of Zb{bar b} and Zc{bar c} couplings from the left-right forward-backward asymmetries. The results have been obtained using 150,000 hadronic Z{sup 0} decays accumulated during the 1993-95 runs with high electron beam polarization.
Date: September 1, 1996
Creator: Mancinelli, G.
Partner: UNT Libraries Government Documents Department

Leptophobic Z{prime} from superstring derived models

Description: It was recently suggested that the reported anomalies in R{sub b} and R{sub c} can be interpreted as the effect of a heavy vector boson that couples to quarks and is universally decoupled from leptons. We examine how an extra gauge boson with this property can arise from superstring derived models. In a specific three generation model we show that the U(1){sub B-L} symmetry combines with the horizontal flavor symmetries to form a universal leptophobic U(1) symmetry. In our model there is an enhancement of the color gauge group from twisted sectors. The enhancement occurs after the breaking of the unifying gauge symmetry by ``Wilson lines.`` The leptophobic U(1) symmetry then becomes a generator of the color SU(4) gauge group. We examine how similar symmetries may appear in other string models without the enhancement. We propose that if the current LEP anomalies persist it may be evidence for a certain class of un-unified superstring models. 15 refs., 4 tabs.
Date: April 1, 1996
Creator: Faraggi, A.E. & Masip, M.
Partner: UNT Libraries Government Documents Department

An improved limit on jet handedness in Z{sup 0} decays

Description: We present the results of an improved search for jet handedness in hadronic decays of Z{sup degree} bosons collected by the SLD experiment at SLAC. Quark and antiquark jets, expected to be oppositely polarized in Z{sup degree} decays, were separated using the large forward-backward quark asymmetry induced by the highly polarized SLC electron beam. The larger data sample and beam polarization of the 1994/5 SLC/SLD run yield a factor of two improvement in our sensitivity to jet handedness. Assuming Standard Model values of quark polarizations we set an improved upper limit on the analyzing power of the handedness method.
Date: July 1995
Creator: Collaboration, The SLD
Partner: UNT Libraries Government Documents Department

Studies of multiparticle production in hadronic Z{sup 0} decays

Description: Hadronic decays of Z{sup 0} bosons produced in e{sup +}e{sup {minus}} annihilation are ideal for testing QCD. This thesis presents a measurement of the charged-particle multiplicity distribution and the first experimental study of the ratio of cumulant to factorial moments, using hadronic Z{sup 0} decays collected by the SLD experiment at SLAC. The author finds that this ratio, as a function of the moment-rank q, decreases sharply to a negative minimum at q = 5, which is followed by quasi-oscillations. These features are in qualitative agreement with expectations from higher-order perturbative QCD. The author also presents an analysis of the intermittency in rapidity phase space using the method of scaled factorial moments. It is found that both parton cascade and hard-gluon radiations contribute to the growth of the moments by studying the event-shape and jet-topology dependencies. All aspects of the data appear to be reproduced reasonably well by the QCD-based Monte Carlo model.
Date: December 1, 1996
Creator: Zhou, Jingchen
Partner: UNT Libraries Government Documents Department

An update on strong W{sub L}W{sub L} scattering at the LHC

Description: The author summarizes an update on the study for a strongly interacting electroweak symmetry breaking sector via longitudinal vector boson scattering at the 14 TeV Large Hadron Collider. In the update, the decay mode ZZ {yields} l{sup +}l{sup {minus}}{nu}{bar {nu}} and a new vector-resonance signal via q{bar q} {yields} V {yields} W{sup +}W{sup {minus}}/W{sup {+-}}Z are also included.
Date: March 1, 1995
Creator: Cheung, K.
Partner: UNT Libraries Government Documents Department

Spin structure in high energy processes: Proceedings

Description: This report contains papers as the following topics: Spin, Mass, and Symmetry; physics with polarized Z{sup 0}s; spin and precision electroweak physics; polarized electron sources; polarization phenomena in quantum chromodynamics; polarized lepton-nucleon scattering; polarized targets in high energy physics; spin dynamics in storage rings and linear accelerators; spin formalism and applications to new physics searches; precision electroweak physics at LEP; recent results on heavy flavor physics from LEP experiments using 1990--1992 data; precise measurement of the left-right cross section asymmetry in Z boson production by electron-positron collisions; preliminary results on heavy flavor physics at SLD; QCD tests with SLD and polarized beams; recent results from TRISTAN at KEK; recent B physics results from CLEO; searching for the H dibaryon at Brookhaven; recent results from the compton observatory; the spin structure of the deuteron; spin structure of the neutron ({sup 3}HE) and the Bjoerken sum rule; a consumer`s guide to lattice QCD results; top ten models constrained by b {yields} sy; a review of the Fermilab fixed target program; results from the D0 experiment; results from CDF at FNAL; quantum-mechanical suppression of bremsstrahlung; report from the ZEUS collaboration at HERA; physics from the first year of H1 at HERA, and hard diffraction. These papers have been cataloged separately elsewhere.
Date: December 1, 1994
Creator: DePorcel, L. & Dunwoodie, C.
Partner: UNT Libraries Government Documents Department

Studies of the strong and electroweak interactions at the Z{sub 0} pole

Description: This thesis presents studies of the strong and electroweak forces, two of the fundamental interactions that govern the behavior of matter at high energies. The authors have used the hadronic decays of Z{sup 0} bosons produced with the unique experimental apparatus of the e{sup +}e{sup {minus}} Linear Collider at the Stanford Linear Accelerator Center (SLAC) and the SLAC Large Detector (SLD) for these measurements. Employing the precision tracking capabilities of the SLD, they isolated samples of Z{sup 0} events containing primarily the decays of the Z{sup 0} to a chosen quark type. With an inclusive selection technique, they have tested the flavor independence of the strong coupling, {alpha}{sub s} by measuring the rates of multi-jet production in isolated samples of light (uds), c, and b quark events. They find: {alpha}{sub s}{sup uds}/{alpha}{sub s}{sup all} 0.987 {+-} 0.027(stat) {+-} 0.022(syst) {+-} 0.022(theory), {alpha}{sub s}{sup c}/{alpha}{sub s}{sup all} = 1.012 {+-} 0.104(stat) {+-} 0.102(syst) {+-} 0.096(theory), {alpha}{sub s}{sup b}/{alpha}{sub s}{sup all} = 1.026 {+-} 0.041(stat) {+-} 0.030(theory), which implies that the strong interaction is independent of quark flavor within the present experimental sensitivity. They have also measured the extent of parity-violation in the Z{sup 0} c{bar c} coupling, given by the parameter A{sub c}{sup 0}, using a sample of fully and partially reconstructed D* and D{sup +} meson decays and the longitudinal polarization of the SLC electron beam. This sample of charm quark events was derived with selection techniques based on their kinematic properties and decay topologies. They find A{sub c}{sup 0} = 0.73 {+-} 0.22(stat) {+-} 0.10(syst). This value is consistent with that expected in the electroweak standard model of particle interactions.
Date: March 1, 1995
Creator: Hildreth, M.D.
Partner: UNT Libraries Government Documents Department

A search for jet handedness in hadronic Z{sup 0} decays

Description: Transport of polarization through hadronization process is one of the fundamental interest in Quantum Chromodynamics which is a theory of strong interactions. In the low energy region where the hadronization occurs, QCD calculations are difficult, therefore at present the transport can be investigated experimentally. In this study the authors have searched for signatures of polarization of quarks and antiquarks in hadronic jets from Z{sup 0} {yields} q{bar q} decays. The polarization of quarks and antiquark produced by Z{sup 0} decays are predicted by the Standard Model of elementary particle physics. The authors defined several quantities depending on {open_quotes}jet handedness{close_quotes} methods and studied the correlation between the predicted polarization and the quantities. The signal was estimated by analyzing power which represents degree of the polarization transport through the hadronization process. The Z{sup 0} decays were measured by SLC Large Detector and the polarized electron beam provided by SLAC Linear Collider was useful for this study. The data from the 1993 run showed no signature of the transport of quark and antiquark polarization. Upper limits on magnitude of the analyzing power were set in the range 0.05-0.15 depending on the methods.
Date: March 1995
Creator: Hasegawa, Yoji
Partner: UNT Libraries Government Documents Department

Searching for new physics with charm

Description: The author considers the prospect of using the charm system as a laboratory for probing new physics. The theoretical expectations for rare charm meson decays, D{sup 0} - {bar D}{sup 0}, and charm quark asymmetries in Z decays are examined in the Standard Model. The effects of new physics from several classes of nonstandard dynamical models are summarized for these phenomena.
Date: June 1995
Creator: Hewett, J. L.
Partner: UNT Libraries Government Documents Department

A test of the flavor independence of strong interactions

Description: The authors present a comparison of the strong couplings of b, c, and light (u, d, and s) quarks derived from multi-jet rates in flavor-tagged samples of hadronic Z{sup 0} decays recorded with the SLC Large detector at the SLAC Linear Collider. By comparing the rates of 3-jet events in these three samples they have extracted: {alpha}{sub s}(uds)/{alpha}{sub s}(all) = 0.97 {+-} 0.03(stat.) {+-} 0.04(syst.) {+-} 0.02(theory), {alpha}{sub s}(c)/{alpha}{sub s}(all) = 1.12 {+-} 0.11(stat.) {+-} 0.10(syst.) {+-} 0.07(theory), {alpha}{sub s}(b)/{alpha}{sub s}(all) = 1.03 {+-} 0.04(stat.) {+-} 0.08(syst.) {+-} 0.02(theory).
Date: July 1, 1994
Creator: Collaboration, SLD
Partner: UNT Libraries Government Documents Department

Preliminary measurements of the time dependence of B{sub d}{sup 0} - {bar B}{sub d}{sup 0} mixing with kaon and charge dipole tags

Description: We report two preliminary measurements of the time dependence of B{sub d}{sup 0}- B{sub d}{sup 0} mixing using novel techniques with a sample of 150,000 hadronic Z{sup O} decays collected by the SLD experiment at the SLC. B decay vertices are reconstructed inclusively with a topological technique and the B hadron flavor at production is determined by exploiting the large left-right forward-backward asymmetry of Z{sup O} {r_arrow} b {bar b} decays in combination with a jet charge technique. Two methods are used to tag the B flavor at decay. The first uses the charge of kaons attached to the B decay vertex and identified with the Cherenkov Ring Imaging Detector. The second measurement is based on the construction of a charge dipole of the topological vertices to separate the B{sub d}{sup O}/B{sub d}{sup 0} decays by exploiting the B {r_arrow} D cascade charge structure. The measurement of the oscillation frequency yields {Delta}m{sub d} = 0.58 {+-} 0.07(stat){+-}0.08(syst) ps{sup -1} and 0.56 {+-} 0.08(stat){+-}0.04(syst) ps{sup {minus}1} for the kaon and dipole tags respectively.
Date: July 1, 1996
Partner: UNT Libraries Government Documents Department

Measurement of Z{sup 0} lepton coupling asymmetries

Description: Polarized Z{sup 0}`s from e{sup +}e{sup {minus}} collisions at the SLAC Linear Collider (SLC) have been used to determine the asymmetry parameters A{sub e}, A{sub {mu}} and A{sub {tau}} from the leptonic decay channels. This is the first direct measurement of A{sub {mu}}. The data have been gathered by the SLC Large Detector (SLD) with the electron polarization averaging 63% during the 1993 data taking period and 77% in 1994-95. A maximum likelihood procedure as well as cross section asymmetries was used to measure the asymmetry parameters from the differential cross sections for equal luminosities of left- and right-handed electron beams. The polarization-dependent muon-pair distributions give A{sub {mu}} = 0.102 {+-}0.034 and the tau-pairs give A{sub {tau}} = 0.195 {+-}0.034. The initial state electronic couplings in all three leptonic channels as well as the final state angular distribution in the e{sup +}e{sup {minus}} final state measure A{sub e} to be A{sub e} = 0.152{+-}0.012. Assuming lepton universality and defining a global leptonic asymmetry parameter A{sub e-{mu}-{tau}} = 0.151{+-}0.011. This global leptonic asymmetry value translates directly into sin{sup 2}{theta}{sub W}{sup eff}=0.2310{+-}0.0014 at the Z{sup 0} pole.
Date: July 1, 1997
Creator: Smy, M.B.
Partner: UNT Libraries Government Documents Department

Observation of Z decays to b quark pairs at the Tevatron Collider

Description: A search for Z boson decays to pairs of b-quark jets has been performed in the full dataset collected with the CDF detector at the Tevatron p{anti p} collider. After the selection of a pure sample of b {anti b} events by means of the identification of secondary vertices from b-quark decays, we have used two kinematic variables to further discriminate the electroweak b {anti b} production from QCD processes, and sought evidence for the Z decay in the dijet invariant mass distribution. An absolute background prediction allows the extraction of an excess of events inconsistent with the background predictions by 3.23{sigma} but in good agreement with the amount and characteristics of the expected signal. We then fit the mass distribution with an unbinned likelihood technique, and obtain a Z {yields} b {anti b} signal amounting to 91 {+-} 30 {+-} 19 events.
Date: July 1, 1998
Creator: Dorigo, T.
Partner: UNT Libraries Government Documents Department

Structure functions of electroweak boson and leptons

Description: The QCD structure of the electroweak bosons is reviewed and the lepton structure function is defined and calculated. The leading order splitting functions of electron into quarks are extracted, showing an important contribution from {gamma}-Z interference. Leading logarithmic QCD evolution equations are constructed and solved in the asymptotic region where log{sup 2} behavior of the Parton densities is observed. Possible applications with clear manifestation of ``resolved`` photon and weak bosons are discussed. 8 refs., 3 figs.
Date: April 2, 1996
Creator: Slominski, W & Szwed, J.
Partner: UNT Libraries Government Documents Department

e{sup +}e{sup {minus}} collisions at the SLC: The left-right asymmetry

Description: The Sanford Linear Collider has operated successfully to produce over 50,000 Z{sup O}{prime}s with polarized electron beams. The asymmetry in the production of Z{sup O}{prime}s with respect to left and right handed electron beams has been measured, and a preliminary result is presented.
Date: February 1, 1994
Creator: Shapiro, G. & Collaboration, SLD
Partner: UNT Libraries Government Documents Department

A Preliminary measurement of the gluon splitting rate into b\bar{b} pairs in hadronic Z0 decays

Description: We present a measurement of the rate of gluon splitting into bottom quarks, g --> b anti-b, in hadronic Z<sup>0</sup> 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 avor. A topological vertex mass technique was used to tag the two jets with the smallest angle between them as b/anti-b. We obtained a rate of g --> b anti-b per hadronic event to be (3.07 ± 0.71(stat:) ± 0.66(syst:)) × 10&sup3; (preliminary).
Date: June 10, 1999
Creator: Abe, Toshinori
Partner: UNT Libraries Government Documents Department

A Test of the Flavor Independence of Strong Interactions in e+e- Annihilation at the Z0 Pole

Description: This thesis presents a comparison of the strong coupling of the gluons to light (q<sub>l</sub> = u + d + s), c, and b quarks, determined from multijet rates in flavor-tagged samples of approximately 150,000 hadronic Z<sup>0</sup> decays recorded with the SLC Large Detector at the SLAC Linear Collider between 1993 and 1995. Flavor separation among primary q<sub>l</sub> {anti q<sub>l</sub>} , c{anti c} and b {anti b} final states was made on the basis of the reconstructed mass of long-lived heavy-hadron decay vertices, yielding tags with high purity and low bias against {>=} 3-jet final states. The data obtained imply no flavor dependence within our sensitivity.
Date: September 3, 1999
Creator: Muller, David
Partner: UNT Libraries Government Documents Department

Combined SLD Measurement of Ab at the Z0 Resonance using Various Techniques

Description: We present a new preliminary combination of measurements of the parity-violation parameter A<sub>b</sub> made by the SLD collaboration using various experimental techniques. The techniques differ in detail, but in general a sample of b anti-b events is selected or enhanced by using the topologically reconstructed mass of the separated vertices formed by decaying B hadrons. The direction of the b(anti-b) quark is signed by one of four final state tags: jet charge, vertex charge, leptons, or identified K<sup>=</sup> from the b vertex. We account for statistical and systematic correlations between the four analyses to arrive at our combined result: A<sub>b</sub> = 0.905 ± 0.017(stat) ± 0.020(syst).
Date: July 27, 1999
Creator: Crawford, Glen D
Partner: UNT Libraries Government Documents Department

Light Threshold Effects in Supersymmetric Grand Unified Theories

Description: Supersymmetric Grand Unified Theories have a rich spectrum of particles barely heavier than the intermediate vector bosons. As their non-supersymmetric counterparts, they lead to many relations among low energy observables. But the precise form of the predictions is modified by the extended spectrum. If the masses of these new particles are comparable to M{sub Z}, the standard computation of their effect becomes inaccurate. The authors, present a detailed discussion of the correct procedure, and carry out the relevant computations to one loop order. Attention is paid to the special treatment that the top and Higgs particles must receive. The size of the effect is explored for a range of parameters in the minimal supersymmetric SU(5) grand-unified theory with radiative breaking. It is found that the naive (leading-log) computation can be fairly inaccurate.
Date: August 1, 1993
Creator: Faraggi, A. E. & Grinstein, B.
Partner: UNT Libraries Government Documents Department

Recent D0 results on Z{gamma} production

Description: We report on a new search for anomalous {ital ZV}{sub {gamma}} ({ital V = Z}, {gamma}) couplings in the {ital Z}({ital ee}){gamma} mode with 89 pb{sup -1} of data. The following limits on anomalous coupling parameters were set at 95% CL: {vert_bar}{ital h{sup V}}{sub 10, 30}{vert_bar} {lt} 1.9, {vert_bar}{ital h{sup V}}{sub 20, 40}{vert_bar} {lt} 0.4. We also report on the first measurement of {ital Z(vv)}{gamma} production at hadron colliders using 14 pb{sup - 1} of data. Sensitivity to anomalous couplings in this channel is twice as good as that for the combined electron and muon channel analysis reported earlier. We set the following 95% CL limits on the {ital ZV}{gamma} couplings: {vert_bar}{ital h{sup V}}{sub 10, 30}{vert_bar} {lt} 0.9, {vert_bar}{ital h{sup V}}{sub 20, 40}{vert_bar} {lt} 0.2 which are the tightest available at the present time.
Date: November 1996
Creator: Landsberg, G.
Partner: UNT Libraries Government Documents Department

Precise measurement of the left-right cross section asymmetry in Z boson production by E{sup +}e{sup {minus}} collisions

Description: The authors present a precise measurement of the left-right cross section asymmetry (A{sub LR}) for Z boson production by e{sup +}e{sup {minus}} collisions. The measurement was performed at a center-of-mass energy of 91.26 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (63.0 {+-} 1.1)%. Using a sample of 49,392 Z decays, they measure A{sub LR} to be 0.1628 {+-} 0.0071 (stat.) {+-} 0.0028(syst.) which determines the effective weak mixing angle to be sin{sup 2} {theta}{sub W}{sup eff} = 0.2292 {+-} 0.0009(stat.) {+-} 0.0004(syst.). They combine this result with the result obtained in 1992 and obtain sin{sup 2} {theta}{sub W}{sup eff} = 0.2294 {+-} 0.0010, which constitutes the best measurement of sin{sup 2} {theta}{sub W}{sup eff} in a single experiment presently available.
Date: September 1, 1994
Creator: Lath, A. & Collaboration, SLD
Partner: UNT Libraries Government Documents Department

Comment on Leptophobic Bosons and nu N Neutral Current Scattering Data

Description: The relevance of existing {nu}{ital N} deep inelastic scattering data to the model of an additional leptophobic vector boson presented at this conference is discussed. It is shown that the neutral current data is in good agreement with the Standard Model and disfavors such a leptophobic boson.
Date: August 1996
Creator: McFarland, K. S.
Partner: UNT Libraries Government Documents Department