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Compositeness test at the FMC with Bhabha scattering

Description: It is possible that quarks and/or leptons have substructure that will become manifest at high energies. Here we investigate the limits on the muon compositeness scale that could be obtained at the First Muon Collider using Bhabha scattering. We study this limit as a function of the collider energy and the angular cut imposed by the detector capability.
Date: January 1, 1998
Creator: Eichten, E.J. & Keller, S.
Partner: UNT Libraries Government Documents Department

Calculations of precursor propagation in dispersive dielectrics.

Description: The present study is a numerical investigation of the propagation of electromagnetic transients in dispersive media. It considers propagation in water using Debye and composite Rocard-Powles-Lorentz models for the complex permittivity. The study addresses this question: For practical transmitted spectra, does precursor propagation provide any features that can be used to advantage over conventional signal propagation in models of dispersive media of interest? A companion experimental study is currently in progress that will attempt to measure the effects studied here.
Date: August 1, 2003
Creator: Bacon, Larry Donald
Partner: UNT Libraries Government Documents Department

Search for Leptoquarks with the D0 detector

Description: We report on D0 searches for leptoquarks (LQ) predicted in extended gauge theories and composite models to explain the symmetry between quarks and leptons. Data samples obtained with the D0 detector from p{bar p} collisions at a center-of-mass energy of 1.96 TeV corresponding to integrated luminosities of 1-4 fb{sup -1} were analyzed. No evidence for the production of such particles were observed and lower limits on leptoquark masses are set.
Date: October 1, 2009
Creator: Uzunyan, Sergey A. & U., /Northern Illinois
Partner: UNT Libraries Government Documents Department

Sea quarks in baryons

Description: A hadron model with sea quark components is proposed. The ground state properties of the baryon octet and decuplet are calculated. The valence quark q{sup 3} component is about 80% for all of these baryons.
Date: December 31, 1995
Creator: Su, W.N.; Qing, D.; Wang, F. & Goldman, T.
Partner: UNT Libraries Government Documents Department

A search for third generation scalar leptoquarks

Description: Leptoquarks (LQ) are particles with both color and lepton number predicted in some gauge theories and composite models. Current theory suggests that leptoquarks would come in three different generations. We report on a search for charge 1/3 third generation leptoquarks produced in p{bar p} collisions at {radical}s = 1.96 TeV using data collected by the D0 detector at Fermilab. Such leptoquarks would decay into a tau-neutrino plus a b-quark with branching fraction B. We present preliminary results on an analysis where both leptoquarks decay into neutrinos giving a final state with missing energy and two b-jets. Using 425(recorded) pb{sup -1} of data, we place limits on {sigma}(p{bar p} {yields} LQ{ovr LQ})B{sup 2} as a function of the leptoquark mass. Assuming B = 1, we excluded at the 95% confidence level scalar third generation leptoquarks with M{sub LQ} < 219 GeV.
Date: August 1, 2006
Creator: Zatserklyaniy, Andriy & U., /Northern Illinois
Partner: UNT Libraries Government Documents Department

Search for quark-lepton compositeness using the Drell-Yan process at D-Zero

Description: We present preliminary results on the search for quark-lepton compositeness using the Drell-Yan process in p{anti p} collisions at {radical}s = 1.8 TeV. If quarks and leptons were composite with common substructure, the dielectron mass spectrum would show an excess in the high mass region relative to the Standard model. We observe no such excess. We set a 95% confidence level lower limit on the compositness scale using a contact interaction model.
Date: September 1, 1998
Partner: UNT Libraries Government Documents Department

Searches for compositeness at the Tevatron

Description: The existence of three families of quarks and leptons suggests the possibility of a substructure for these objects. The hypothetical constituents known generically as preons, interact via a new strong interaction called Metacolor. The characteristic energy scale, {Lambda}, for the new interactions is, of course, unknown. The strength of the interactions through a contact term can be written as {cflx s}/({alpha}{sub S}{Lambda}{sup 2}), where {cflx s} is the square of the energy in the center of mass frame of the (normal) interacting partons, and {alpha}{sub S} is the QCD coupling. The first limit on the size of the atomic nucleus was obtained by Geiger and Mardsen in the Rutherford scattering of {alpha} particles from nuclei. In an analogous way, the authors can set a limit on the size of quarks and leptons by observing the scattering of the highest energy quarks and antiquarks at the Fermilab Tevatron at {bar p}p center-of-mass energy of 1.8 TeV for collider experiments, and proton beam energy of 0.8 TeV for fixed-target experiments. The collider detectors at Fermilab, CDF and D0, have performed searches for compositeness, and this paper gives a summary of those searches. Those detectors are general-purpose, have nearly 4{pi} acceptance, and measure lepton and jet energies to high precision. In addition, the neutrino detector, CCFR, which utilized the 800 GeV proton line at Fermilab has performed a compositeness search.
Date: May 11, 2000
Creator: Green, J. Andrew
Partner: UNT Libraries Government Documents Department

Transition from hadronic to partonic interactions for a composite spin-1/2 model of a nucleon

Description: A simple model of a composite nucleon is developed in which a fermion and a boson, representing quark and diquark constituents of the nucleon, form a bound state owing to a contact interaction. Photon and pion couplings to the quark provide vertex functions for the photon and pion interactions with the composite nucleon. By a suitable choice of cutoff parameters of the model, realistic electromagnetic form factors are obtained. When a pseudoscalar pion-quark coupling is used, the pion-nucleon coupling is predominantly pseudovector. A virtual photopion amplitude is considered in which there are two types of contributions: hadronic contributions where the photon and pion interactions have an intervening propagator of the nucleon or its excited states, and contact-like contributions where the photon and pion interactions occur within a single vertex. At large Q, the contact-like contributions are dominant. The model nucleon exhibits scaling behavior in deep-inelastic scattering and the normalization of the parton distribution provides a rough normalization of the contact-like contributions. Calculations for the virtual photopion amplitude are performed using kinematics appropriate to its occurrence as a meson-exchange current in electron-deuteron scattering. The results show that the contact-like terms can dominate the meson-exchange current for Q > 1 GeV/c. There is a direct connection of the contact-like terms to the off-forward parton distributions of the model nucleon.
Date: February 1, 2000
Creator: Tjon, J.A. & Wallace, S.J.
Partner: UNT Libraries Government Documents Department

A search for charge 1/3 third generation leptoquarks in muon channels

Description: Leptoquarks are exotic particles that have color, electric charge, and lepton number and appear in extended gauge theories and composite models. Current theory suggests that leptoquarks would come in three different generations corresponding to the three quark and lepton generations. We are searching for charge 1/3 third generation leptoquarks produced in p{bar p} collisions at {radical}s = 1.96 TeV using data collected by the D0 detector. Such leptoquarks would decay into either a tau-neutrino plus a b-quark or, if heavy enough, to a tau-lepton plus a t-quark. We present preliminary results on an analysis where both leptoquarks decay into neutrinos giving a final state with missing energy and two b-quarks using 367 pb{sup -1} of Run II D0 data taken between August 2002 and September 2004. We place upper limits on {sigma}(p{bar p} {yields} LQ{ovr LQ})B{sup 2} as a function of the leptoquark mass M{sub LQ}. Assuming B = 1, we exclude at the 95% confidence level third generation leptoquarks with M{sub LQ} < 197 GeV/c{sup 2}.
Date: August 1, 2006
Creator: Uzunyan, Sergey A. & U., /Northern Illinois
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

Sensitivity to quark and lepton compositeness at the Tevatron

Description: We present a study of the sensitivity of CDF to quark and lepton compositeness assuming 2 fb{sup -1} (Run II) and 30 fb{sup -1} (TeV33) of integrated luminosity for future Tevatron collider runs. We calculate the expected number of Drell-Yan dielectron events in the standard model, and compare it to the predicted number of events from a {ital q{anti q}} {r_arrow} {ital e{anti e}} left-handed contact interaction, as a function of dielectron invariant mass, for various values of the compositeness scale, {Lambda}. Preliminary CDF limits on a {ital q{anti q}} {r_arrow} {ital l{anti l}} contact interaction scale using 110 pb{sup -1} of Run I data are between 3 and 4 TeV, depending on the channel and theoretical model. With 2 fb{sup -1} of integrated luminosity in Run II, the Tevatron will be sensitive to a compositeness scale of {Lambda}{sup +} {<=} 6.5 TeV and {Lambda}{sup -} {<=} 10 TeV. Assuming present detector performance, with 30 fb{sup -1} of integrated luminosity from TeV33, the Tevatron will be sensitive to a compositeness scale of {Lambda}{sup +} {<=} 14 TeV and {Lambda}{sup -} {<=} 20 TeV, in the {ital ee} channel.
Date: October 1, 1996
Creator: de Barbaro, P.; Bodek, A.; Kim, B.J.; Fan, Q. & Harris, R.
Partner: UNT Libraries Government Documents Department

Probing contact interactions at high energy lepton colliders

Description: Fermion compositeness and other new physics can be signaled by the presence of a strong four-fermion contact interaction. Here the authors present a study of {ell}{ell}qq and {ell}{ell}{ell}{prime}{ell}{prime} contact interactions using the reactions: {ell}{sup +}{ell}{sup {minus}} {r_arrow} {ell}{prime}{sup +} {ell}{prime}{sup {minus}}, b{anti b}, c{anti c} at future e{sup +}e{sup {minus}} linear colliders with {radical}s = 0.5--5 TeV and {mu}{sup +}{mu}{sup {minus}} colliders with {radical}s = 0.5, 4 TeV. They find that very large compositeness scales can be probed at these machines and that the use of polarized beams can unravel their underlying helicity structure.
Date: December 1, 1996
Creator: Cheung, K.; Godfrey, S. & Hewett, J.A.
Partner: UNT Libraries Government Documents Department

Searches for exotics at the Tevatron

Description: The Fermilab Tevatron collider experiments CDF and D0 collected more than 100 pb{sup -1} of data at {radical}(s) = 1.8 TeV during Run I (1992-1995). Results of searches for new phenomena (exotics) are presented, covering supersymmetry, leptoquarks, technicolor, and quark compositeness. In each case, no discrepancy with the Standard Model is observed, and stringent limits on new physics predicted by these models are extracted. Parameters for Run II of the Tevatron are given along with projections of search reaches for this upcoming run.
Date: June 22, 2000
Creator: Chertok, Maxwell
Partner: UNT Libraries Government Documents Department

Run II jet physics: Proceedings of the Run II QCD and weak boson physics workshop

Description: The Run II jet physics group includes the Jet Algorithms, Jet Shape/Energy Flow, and Jet Measurements/Correlations subgroups. The main goal of the jet algorithm subgroup was to explore and define standard Run II jet finding procedures for CDF and D0. The focus of the jet shape/energy flow group was the study of jets as objects and the energy flows around these objects. The jet measurements/correlations subgroup discussed measurements at different beam energies; {alpha}{sub S} measurements; and LO, NLO, NNLO, and threshold jet calculations. As a practical matter the algorithm and shape/energy flow groups merged to concentrate on the development of Run II jet algorithms that are both free of theoretical and experimental difficulties and able to reproduce Run I measurements. Starting from a review of the experience gained during Run I, the group considered a variety of cone algorithms, and K{sub T} algorithms. The current understanding of both types of algorithms, including calibration issues, are discussed in this report along with some preliminary experimental results. The jet algorithms group recommends that CDF and D0 employ the same version of both a cone algorithm and a K{sub T} algorithm during Run II. Proposed versions of each type of algorithm are discussed. The group also recommends the use of full 4-vector kinematic variables whenever possible. The recommended algorithms attempt to minimize the impact of seeds in the case of the cone algorithm and preclustering in the case of the K{sub T} algorithm. Issues regarding precluster definitions and merge/split criteria require further study.
Date: May 11, 2000
Creator: al., Gerald C. Blazey et
Partner: UNT Libraries Government Documents Department

Modeling Three-Dimensional Groundwater Flow and Advective Contaminant Transport at a Heterogeneous Mountainous Site in Support of Remediation Strategy

Description: A calibrated groundwater flow model for a contaminated site can provide substantial information for assessing and improving hydraulic measures implemented for remediation. A three-dimensional transient groundwater flow model was developed for a contaminated mountainous site, at which interim corrective measures were initiated to limit further spreading of contaminants. This flow model accounts for complex geologic units that vary considerably in thickness, slope, and hydrogeologic properties, as well as large seasonal fluctuations of the groundwater table and flow rates. Other significant factors are local recharge from leaking underground storm drains and recharge from steep uphill areas. The zonation method was employed to account for the clustering of high and low hydraulic conductivities measured in a geologic unit. A composite model was used to represent the bulk effect of thin layers of relatively high hydraulic conductivity found within bedrock of otherwise low conductivity. The inverse simulator ITOUGH2 was used to calibrate the model for the distribution of rock properties. The model was initially calibrated using data collected between 1994 and 1996. To check the validity of the model, it was subsequently applied to predicting groundwater level fluctuation and groundwater flux between 1996 and 1998. Comparison of simulated and measured data demonstrated that the model is capable of predicting the complex flow reasonably well. Advective transport was approximated using pathways of particles originating from source areas of the plumes. The advective transport approximation was in good agreement with the trend of contaminant plumes observed over the years. The validated model was then refined to focus on a subsection of the large system. The refined model was subsequently used to assess the efficiency of hydraulic measures implemented for remediation.
Date: January 14, 2004
Creator: Zhou, Quanlin; Birkholzer, Jens T.; Javandel, Iraj & Jordan, Preston D.
Partner: UNT Libraries Government Documents Department

Pursuing the origin of electroweak symmetry breaking: a 'Bayesian Physics' argument for sqrt(s) <~; 600 GeV e+e- collider

Description: High-energy data has been accumulating over the last ten years, and it should not be ignored when making decisions about the future experimental program. In particular, we argue that the electroweak data collected at LEP, SLC and Tevatron indicate a light scalar particle with mass less than 500 GeV. This result is based on considering a wide variety of theories including the Standard Model, supersymmetry, large extra dimensions, and composite models. We argue that a high luminosity, 600 GeV e{sup +}e{sup -} collider would then be the natural choice to feel confident about finding and studying states connected to electroweak symmetry breaking. We also argue from the data that worrying about resonances at multi-TeV energies as the only signal for electroweak symmetry breaking is not as important a discovery issue for the next generation of colliders. Such concerns should perhaps be replaced with more relevant discovery issues such as a Higgs boson that decays invisibly, and ''new physics'' that could conspire with a heavier Higgs boson to accommodate precision electroweak data. An e{sup +}e{sup -} collider with {radical}s {approx}&lt; 600 GeV is ideally suited to cover these possibilities.
Date: August 9, 2000
Creator: Kane, G.L. & Wells, James D.
Partner: UNT Libraries Government Documents Department

Confinement at large-N. [N = number of colors]

Description: Recent numerical results indicate that QCD in the limit of an infinite number (N) of colors also has confinement and moreover that it looks rather similar to normal QCD with N = 3 colors. This imposes severe restrictions on what the mechanism of confinement can be.
Date: June 1, 1985
Creator: Klinkhamer, F.R.
Partner: UNT Libraries Government Documents Department

Small scale structure on cosmic strings

Description: I discuss our current understanding of cosmic string evolution, and focus on the question of small scale structure on strings, where most of the disagreements lie. I present a physical picture designed to put the role of the small scale structure into more intuitive terms. In this picture one can see how the small scale structure can feed back in a major way on the overall scaling solution. I also argue that it is easy for small scale numerical errors to feed back in just such a way. The intuitive discussion presented here may form the basis for an analytic treatment of the small structure, which I argue in any case would be extremely valuable in filling the gaps in our resent understanding of cosmic string evolution. 24 refs., 8 figs.
Date: October 30, 1989
Creator: Albrecht, A.
Partner: UNT Libraries Government Documents Department

Evolution of cosmic string networks

Description: We summarize our new results on cosmic strings. These results include: the application of non-equilibrium statistical mechanics to cosmic string evolution, a simple ''one scale'' model for the long strings which has a great deal of predictive power, results from large scale numerical simulations, and a discussion of the observational consequences of our results. An upper bond on G/mu/ of approximately 10/sup /minus/7/ emerges from the millisecond pulsar gravity wave bound. We discuss how numerical uncertainties affect this. Any changes which weaken the bound would probably also give the long strings the dominant role in producing observational consequences. 22 refs.
Date: June 1, 1989
Creator: Albrecht, A. & Turok, N.
Partner: UNT Libraries Government Documents Department

Phenomenological implications of the blown-up orbifolds

Description: We discuss the structure of the effective Lagrangian for the (2,2) Z/sub N/ orbifolds and the corresponding Calabi-Yau manifolds which are obtained by ''blowing-up'' the orbifold singularities. The method to ''blow-up'' such singularities is reviewed. Results are exact at the string tree-level. In particular, the question of generating an intermediate scale M/sub I/ in such models is addressed. It is shown that for Z/sub N/ orbifolds (except one) and the corresponding blown-up orbifolds which are compactified on any six-torus T/sup 6/ which can be obtained by continuously deforming T/sup 4/ circle times T/sup 2/, all the terms of the type (2727)/sup K/ are absent from the effective superpotential, thus questioning the mechanism for generating a large intermediate scale for such compactifications.
Date: May 1, 1987
Creator: Cvetic, M.
Partner: UNT Libraries Government Documents Department

Report of the 2005 Snowmass Top/QCD Working Group

Description: This report discusses several topics in both top quark physics and QCD at an International Linear Collider (ILC). Issues such as measurements at the t tbar threshold, including both theoretical and machine requirements, and the determination of electroweak top quark couplings are reviewed. New results concerning the potential of a 500 GeV e+e collider for measuring Wtb couplings and the top quark Yukawa coupling are presented. The status of higher order QCD corrections to jet production cross sections, heavy quark form factors, and longitudinal gauge boson scattering, needed for percent-level studies at the ILC, are reviewed. A new study of the measurement of the hadronic structure of the photon at a gamma gamma collider is presented. The effects on top quark properties from several models of new physics, including composite models, Little Higgs theories, and CPT violation, are studied.
Date: January 17, 2006
Creator: Juste, A.; Kiyo, Y.; Petriello, F.; Teubner, T.; Agashe, K.; Batra, P. et al.
Partner: UNT Libraries Government Documents Department