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Measurement of sin {sup 2}{Theta}{sub W} at the First Muon Collider

Description: This report summarizes the study of the possibility of measuring sin{sup 2}{theta}{sub W} using the intense neutrino beam expected from the straight sections of the First Muon Collider ring. This study is based on realistic error calculations from the CCFR and the NuTeV experiments. Using a neutrino detector that is capable of identifying and distinguishing electrons and muons, along with a light isoscalar target, it is conceivable to measure sin{sup 2}{theta}{sub W} to the precision equivalent to the W mass uncertainty (experimental) of 30 MeV.
Date: January 1, 1998
Creator: Yu, J. & Kotwal, A.V.
Partner: UNT Libraries Government Documents Department

Determination of sin{superscript 2} theta {subscript W} in neutrino-nucleon scattering at the NuTeV

Description: We report the determination of sin{sup 2}{theta}{sub W} in {nu}-N deep inelastic scattering from the NuTeV experiment. Using separate neutrino and anti-neutrino beams, NuTeV is able to extract sin{sup 2}{theta}{sub W} with low systematic errors from the Paschos-Wolfenstein variable R{sup -}, a ratio of differences of neutrino and anti-neutrino neutral-current and charged-current cross-sections. NuTeV measures sin{sup 2}{theta}{sub W} {sup (on - shell)} = 0.2253 {+-} 0.0019(stat) {+-} 0.0010(syst), which implies M{sub W}= 80.26 {+-} 0.11 GeV.
Date: April 29, 1999
Creator: al., R. Bernstein et
Partner: UNT Libraries Government Documents Department

Mass hierarchies from anomalies: A peek behind the Planck curtain

Description: The masses of quarks and leptons suggest a strong hierarchical structure. We argue that their patterns can be reproduced through the introduction of a new Abelian symmetry. The data suggest that this symmetry is anomalous. We suggest that the cancellation of its anomalies occurs through the Green-Schwarz mechanism. An important check of this idea is that it links the Weinberg angle to a mass ration of the elementary fermions. The Green-Schwarz mechanism occurs naturally in many superstring compactifications, and produces a small parameter, which we use to determine the quark mass hierarchy. We show that hierarchy and mixings among the chiral fermions is a consequence of the Green-Schwarz mechanism. We present several models where this idea is realized. 16 refs., 2 tabs.
Date: May 1, 1996
Creator: Ramond, P.
Partner: UNT Libraries Government Documents Department

Consequences of an Abelian family symmetry

Description: The addition of an Abelian family symmetry to the Minimal Super-symmetric Standard Model reproduces the observed hierarchies of quark and lepton masses and quark mixing angles, only if it is anomalous. Green-Schwarz compensation of its anomalies requires the electroweak mixing angle to be sin{sup 2}{theta}{sub {omega}} = 3/8 at the string scale, without any assumed GUT structure, suggesting a superstring origin for the standard model. The analysis is extended to neutrino masses and the lepton mixing matrix.
Date: January 1, 1996
Creator: Ramond, P.
Partner: UNT Libraries Government Documents Department

Anomalous Abelian symmetry in the standard model

Description: The observed hierarchy of quark and lepton masses can be parametrized by nonrenormalizable operators with dimensions determined by an anomalous Abelian family symmetry, a gauge extension to the minimal supersymmetric standard model. Such an Abelian symmetry is generic to compactified superstring theories, with its anomalies compensated by the Green-Schwarz mechanism. If we assume these two symmetries to be the same, we find the electroweak mixing angle to be sin {sup 2}{theta}{sub {omega}} = 3/8 at the string scale, just by setting the ratio of the product of down quark to charged lepton masses equal to one at the string scale. This assumes no GUT structure. The generality of the result suggests a superstring origin for the standard model. We generalize our analysis to massive neutrinos, and mixings in the lepton sector.
Date: December 31, 1995
Creator: Ramond, P.
Partner: UNT Libraries Government Documents Department

Results of the LSND search for {ovr {nu}}{sub {mu}} {yields} {ovr {nu}}{sub e} oscillations

Description: A search for {ovr {nu}}{sub {mu}}{yields}{ovr {nu}}{sub e} oscillations has been conducted at the Los Alamos Meson Physics Facility by using {ovr {nu}}{sub {mu}} from {mu}{sup +} decay at rest. The {ovr {nu}}{sub e} are detected via the reaction {ovr {nu}}{sub e}p {yields} e{sup +} n , correlated with a {gamma} from np {yields} d{gamma} (2.2 MeV). The use of tight cuts to identify e{sup +} events with correlated {gamma} rays yields 22 events with e{sup +} energy between 36 and 60 MeV and only 4.6 {plus_minus} 0.6 background events. The probability that this observation can be explained by statistical fluctuation is less than 10{sup -7}. Assuming these events are due to oscillations, a likelihood fit to all the e{sup +} events between 20 and 60 MeV has been performed to extract the oscillation parameters sin{sup 2} 2{theta} and {Delta}m{sup 2}. The favored region resulting from this fit is shown.
Date: July 1, 1996
Creator: Federspiel, F.J.
Partner: UNT Libraries Government Documents Department

Yukawa textures with an anomalous horizontal abelian symmetry

Description: The observed hierarchy of quark and lepton masses and mixings may be obtained by adding an abelian family symmetry to the Minimal Supersymmetric Model and coupling quarks and leptons to an electroweak singlet scalar field. In a large class of such models, this symmetry suffers from anomalies which must be compensated by the Green-Schwarz mechanism; this in turn fixes the electroweak mixing angle to be sin{sup 2}{theta}{sub W} = 3/8 at the string scale, without any assumed GUT structure. The analysis is extended to two distinct generalizations of the Standard Model: neutrino masses and mixings and R-parity violating interactions. (author). 31 refs., 2 tabs.
Date: January 1996
Creator: Binetruy, P.; Lavignac, S. & Ramond, P.
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

Direct and indirect measurements of the W boson mass at Fermilab

Description: Presented are the direct measurements of the W boson mass from the CDF and D0 experiments at the Fermilab p{bar p} collider using data from the 1994--1995 run. The W from the D0 experiment is 80.44 {+-} 0.12 GeV and the preliminary mass from CDF is 80.43 {+-} 0.16 GeV. Combining these mass values with the previous Tevatron measurements leads to a M{sub W} 80.41 {+-} 0.09 GeV. Also, presented is the new measurement of sin{sup 2} {Theta}{sub W}{sup on-shell} = 0.2199 {+-} 0.0020(stat) {+-} 0.0009(syst) from the deep inelastic neutrino scattering experiment (NuTeV) at Fermilab. In the context of the Standard Model this can be interpreted as a M{sub W} = 80.53 {+-} 0.11 GeV.
Date: June 1, 1998
Creator: Flattum, E.
Partner: UNT Libraries Government Documents Department

Precision electroweak physics at future collider experiments

Description: We present an overview of the present status and prospects for progress in electroweak measurements at future collider experiments leading to precision tests of the Standard Model of Electroweak Interactions. Special attention is paid to the measurement of the {ital W} mass, the effective weak mixing angle, and the determination of the top quark mass. Their constraints on the Higgs boson mass are discussed.
Date: November 1, 1996
Creator: Baur, U. & Demarteau, M.
Partner: UNT Libraries Government Documents Department

Recent Results from the Tevatron

Description: We review recent results from fixed-target and collider experiments at the Fermilab Tevatron. Among the topics discussed are jet production rates, {alpha}{sub S} measurements, the {anti d}/{anti u} ratio in the proton sea, diffraction, heavy quark physics and leptoquark searches.
Date: June 1, 1998
Creator: Demorden, L.
Partner: UNT Libraries Government Documents Department

DIS prospects at the future muon collider facility

Description: We discuss prospects of deep inelastic scattering physics capabilities at the future muon collider facility. In addition to {mu}{sup +}{mu}{sup -} collider itself, the facility provides other possibilities. Among the possibilities, we present muon-proton collider and neutrino fixed target programs at the muon collider facility. This {mu}-p collider program extends kinematic reach and luminosity by an order of magnitude, increasing the possibility of search for new exotic particles. Perhaps most intriguing DIS prospects come from utilizing high intensity neutrino beam resulting from continuous decays of muons in various sections of the muon collider facility. One of the most interesting findings is a precision measurement of electroweak mixing angle, sin{sup 2}{theta}{sub W}, which can be achieved to the precision equivalent to {delta}M{sub W}{approximately} 30MeV.
Date: July 1, 1998
Creator: Yu, J., FERMI
Partner: UNT Libraries Government Documents Department

Measurements of AP{sub LR}, A{sub lepton} and A{sub b} from SLD

Description: We present the measurements of the leptonic asymmetries in Z{sup 0} decays measured by the SLD experiment at SLAC. A data sample of approximately 550,000 Z{sup 0} bosons are used for the preliminary measurement of A{sub LR}(A{sub e}) and the leptonic final state measurements of A{sub e}, A{sub {mu}} and A{sub {tau}}, representing the entire set of 1992-1998 SLD runs. When combining all results, a preliminary value for the effective weak mixing angle is obtained: sin{sup 2} {theta}{sub W}{sup eff} = 0.23109 {+-} 0.00029. We also present the direct measurements of A{sub b} from left-right forward-backward asymmetries, using partial data samples from 1993-1998 SLD runs. The preliminary value combines jet charge, cascade kaon and semileptonic decay analyses to obtain A{sub b} = 0.866 {+-} 0.036.
Date: March 19, 1999
Creator: Fernandez, Jorge P.
Partner: UNT Libraries Government Documents Department

Precision measurement of sin(squared) {theta}{sub W} from {nu}-N scattering at NuTeV and direct measurements of M{sub W}

Description: We present the preliminary result of sin{sup 2}{theta}{sub W} from {nu}-N deep inelastic scattering experiment, NuTeV, at Fermilab. This measurement of sin{sup 2}{theta}{sub W} comes from measuring the Paschos-Wolfenstein parameter R=({sigma}{sup {nu}}{sub NC}-{sigma}{sup {anti {nu}}}{sub NC}), using separate beams of {nu} and {anti {nu}}, utilizing the SSQT. The resulting value of sin{sup 2}{theta}{sub W}{sup on-shell} is 0.2253 {+-} 0.0019(stat) {+-} 0.0010(syst). This value is equivalent to the mass of the W boson, M{sub W} = 80.26 {+-} 0.11 GeV/c{sup 2}. We also summarize the direct measurements of M{sub W} from the Tevatron {anti p}p collider experiments, D0 and CDF. Combining these two direct measurements yields M{sub W} = 80.37 {+-} 0.08 GeV/c{sup 2}.
Date: August 1, 1998
Creator: Yu, J.
Partner: UNT Libraries Government Documents Department

Review of weak mixing angle results at SLC and LEP

Description: In this paper, the authors review recent precise measurements of the weak mixing angle by the SLD experiment at SLC and by the ALEPH, DELPHI, L3, and OPAL experiments at LEP. If they assume that the Minimal Standard Model provides a complete description of the quark and lepton couplings to the Z boson, they find sin{sup 2} {theta}{sub W}{sup eff} = 0.23143 {+-} 0.00028. If this assumption is relaxed to apply to lepton couplings only, they find sin{sup 2}{theta}{sub W}{sup eff} = 0.23106 {+-} 0.00035. They compare these results with other precision electroweak tests.
Date: October 1, 1995
Creator: Woods, M.
Partner: UNT Libraries Government Documents Department

Left-right forward-backward asymmetry for c and b quarks

Description: This report reviews preliminary direct measurements of A{sub b} and A{sub c} from a sample of 100,000 hadronic Z{sup 0} decays accumulated during the 1994-1995 run with a luminosity-weighted average e{sup -} polarization {vert_bar}P{sub e}{vert_bar} {approx} 77.3 {+-} 0.6% combined with another 50,000 events from the 1993 run with {vert_bar}P{sub e}{vert_bar} = 63.0 {+-} 1.1%. The description of SLD detector components can be found in references of the individual analysis papers. All asymmetry measurement results described in this paper apply cos{theta}-dependent QCD corrections.
Date: October 1, 1995
Creator: Huber, J.
Partner: UNT Libraries Government Documents Department

VMD, the WZW Lagrangian and ChPT:The Third Mixing Angle

Description: We show that the Hidden Local Symmetry Model, supplemented with well-known procedures for breaking flavor SU(3) and nonet symmetry, provides all the information contained in the standard Chiral Perturbation Theory (ChPT) Lagrangian L{sup (0)} + L{sup (1)}. This allows to rely on radiative decays of light mesons (VP{gamma} and P{gamma}{gamma}) in order to extract some numerical information of relevance to ChPT: a value for {Lambda}{sub 1} = 0.20 {+-} 0.04, a quark mass ratio of {approx_equal} 21.2 {+-} 2.4, and a negligible departure from the Gell-Mann--Okubo mass formula. The mixing angles are {theta}{sub 8} = {minus}20.40{degree} {+-} 0.96{degree} and {theta}{sub 0} = {minus}0.05{degree} {+-} 0.99{degree}. We also give the values of all decay constants. It is shown that the common mixing pattern with one mixing angle {theta}{sub P} is actually quite appropriate and algebraically related to the {eta}/{eta}{prime} mixing pattern presently preferred by the ChPT community. For instance the traditional {theta}{sub p} is functionally related to the ChPT {theta}{sub 8} and fulfills {theta}{sub P} {approx_equal} {theta}{sub 8}/2. The vanishing of {theta}{sub 0}, supported by all data on radiative decays, gives a novel relation between mixing angles and the violation of nonet symmetry in the pseudoscalar sector. Finally, it is shown that the interplay of nonet symmetry breaking through U(3) {r_arrow} SU(3) x U(1) satisfies all requirements of the physics of radiative decays without any need for additional glueballs.
Date: March 31, 1999
Creator: O'Connell, Heath B
Partner: UNT Libraries Government Documents Department

Electroweak Results from the SLD Experiment

Description: We present an overview of the electroweak physics program of the SLD experiment at the Stanford Linear Accelerator Center (SLAC). A data sample of 550K Z{sup 0} decays has been collected. This experiment utilizes a highly polarized electron beam, a small interaction volume, and a very precise pixel vertex detector. It is the first experiment at a linear electron collider. We present a preliminary result for the weak mixing angle, sin{sup 2}({theta}{sub W}{sup eff}) = 0.23110 {+-} 0.00029. We also present a preliminary result for the parity violating parameter, A{sub b} = 0.898 {+-} 0.029. These measurements are used to test for physics beyond the Standard Model.
Date: May 7, 1999
Creator: Woods, Michael B
Partner: UNT Libraries Government Documents Department

Construction of. Delta. m sup 2 --sin sup 2 2. theta. plots

Description: In the two-flavor approximation, the probability for a neutrino to oscillate from one flavor to the other is given by {Rho}{sub {nu}a}{yields}{sub {nu}b} = sin{sup 2} 2{theta} sin{sup 2} (1.27 {Delta}m{sup 2} L/E{sub {nu}}) where {theta} is the mixing angle, {Delta}m{sup 2} = {vert bar}m{sub {nu}a}{sup 2} {minus} m{sub {nu}b}{sup 2}{vert bar} is measured in (eV/c{sup 2}){sup 2}, L, the distance from the source, is measured in km, and E, the beam energy, is measured in GeV. If either {Delta}m{sup 2} or sin{sup 2} 2{Theta} is zero, there is no oscillation. They might also have small, non-zero values, causing the oscillations to be so small as to be unobservable in a particular experiment. They may also have values which allow us to determine the probability of oscillation, but so far no compelling evidence for oscillation exists. The universal method of portraying what region of parameter space is explored by a neutrino oscillation experiment is to mark off an area on a {Delta}m{sup 2} vs. sin{sup 2} 2{theta} plot. Typically, a line is graphed, with the claim that if the experiment finds not evidence of oscillation, one can, for example, be 90% certain that {Delta}m{sup 2} and sin{sup 2} 2{theta} lie within the region below and to the left of the line. Since these plots are so widely used, it is useful to understand the process by which they are created.
Date: January 1, 1991
Creator: Snyder, R. (Oberlin Coll., OH (United States). Dept. of Physics) & Goodman, M. (Argonne National Lab., IL (United States))
Partner: UNT Libraries Government Documents Department

Neutral current couplings of leptons to polarized Z{sup O}`s in the SLD experiment

Description: The authors study neutral current couplings of leptons to polarized Z{sup 0}`s in the SLD experiment in terms of the leptonic asymmetry parameters A{sub e}, A{sub {mu}}, and A{sub {tau}}. The authors discuss in detail e{sub L,R}{sup {minus}} + e{sup +} {yields} Z{sup 0} {yields} {mu}{sup {minus}}{mu}{sup +} and {tau}{sup {minus}}{tau}{sup +}, with left (L)- or right (R)-handed polarized electron beams. SLD`s most precise measurement of A{sub e} is shown to result from the left-right cross section asymmetry; A{sub LR}; where the dependence on initial state electronic couplings enable use of essentially all of the data. Comparing A{sub {mu}} and A{sub {tau}} with A{sub e} tests the universality of leptonic couplings. A{sub {mu}} = 0.102 {+-} 0.033 {+-} 0.001, A{sub {tau}} = 0.190 {+-} 0.034 {+-} 0.001, and A{sub e} = 0.148 {+-} 0.016 {+-} 0.002 from these two leptonic channels. If lepton universality is assumed, a combined asymmetry parameter A{sub e{mu}{tau}} = 0.147 {+-} 0.013 results, which directly corresponds to an effective value of the weak mixing angle sin{sup 2}{theta}{sub W}{sup eff} = 0.2315 {+-} 0.0017.
Date: December 1, 1996
Creator: Panvini, R.S
Partner: UNT Libraries Government Documents Department

Determination of electroweak parameters at the SLC

Description: We present an improved measurement of the left-right cross section asymmetry (A{sub LR}) for Z{sup 0} boson production by e{sup +}e{sup -} 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) during the 1994-95 running period. The luminosity-weighted average polarization of the SLC electron beam during this run was measured to be (77.23 {+-} 0.52)%. Using a sample of 93,644 hadronic Z{sup 0} decays, we measure the pole asymmetry A{sub LR}{sup 0} to be 0.1512 {+-} 0.0042(stat.) {+-} 0.0011(syst.) which is equivalent to an effective weak mixing angle of sin{sup 2} {theta}{sub W}{sup eff} = 0.23100 {+-} 0.00054(stat.) {+-} 0.00014(syst.). We also present a preliminary direct measurement of the Z{sup 0}-lepton coupling asymmetries A{sub e}, A{sub {mu}}, and A{sub {tau}} extracted from the differential cross section observed in leptonic Z{sup 0} decays. We combine these results with our previous A{sub LR} measurement to obtain a combined determination of the weak mixing angle sin{sup 2} {theta}{sub W}{sup eff} = 0.23061 {+-} 0.00047.
Date: September 1, 1996
Creator: Torrence, E.
Partner: UNT Libraries Government Documents Department

Updated electroweak measurements from neutrino-nucleon deeply inelastic scattering at CCFR

Description: We report the results of a study of electroweak parameters from observations of neutral current {nu}N deeply inelastic scattering in the CCFR detector at the FNAL Tevatron Quadrupole Triplet neutrino beam. An improved extraction of the weak mixing angle in the on-shell renormalization scheme, incorporating additional data and with an improved technique for constraining systematic errors, is presented. Within the Standard Model, this result constrains the W mass with a precision comparable to that from direct measurements. The result is also presented in a model-independent form, as constraints on neutral current quark-neutrino couplings, to facilitate comparisons with theories outside the Standard Model. Using this result, limits on new four-fermion interactions, lepto-quarks and neutrino oscillations are presented. Prospects for a successor experiment, NuTeV (FNAL-E815), are also presented.
Date: August 1, 1996
Creator: McFarland, K.S. & Collaboration, CCFR /NuTeV
Partner: UNT Libraries Government Documents Department

Top quark studies at hadron colliders

Description: The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag {ital b} quark jets in candidate events. The most recent measurements of top quark properties by the CDF and D{null} collaborations are reviewed, including the top quark cross section, mass, branching fractions and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.
Date: August 1, 1996
Creator: Sinervo, P. K.
Partner: UNT Libraries Government Documents Department