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4,170 Matching Results
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Measurement of the cross section for t anti-t production in p anti-p collisions using the kinematics of lepton + jets events
The authors present a measurement of the top pair production cross section in p{bar p} collisions at {radical}s = 1.96 TeV. We collect a data sample with an integrated luminosity of 194 {+-} 11 pb{sup -1} with the CDF II detector at the Fermilab Tevatron. We use an artificial neural network technique to discriminate between top pair production and background processes in a sample of 519 lepton + jets events, which have one isolated energetic charged lepton, large missing transverse energy and at least three energetic jets. We measure the top pair production cross section to be {sigma}{sub t{bar t}} = 6.6 {+-} 1.1 {+-} 1.5 pb, where the first uncertainty is statistical and the second is systematic.
Date:
April 1, 2005
Creator:
Acosta, D.; Adelman, J.; Affolder, Anthony A.; Akimoto, T.; Albrow, M. G.; Ambrose, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the moments of the hadronic invariant mass distribution in semileptonic B decays
None
Date:
February 1, 2005
Creator:
Acosta, D.; Adelman, J.; Affolder, Anthony A.; Akimoto, T.; Albrow, M. G.; Ambrose, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the forward-backward charge asymmetry from W ---> e nu production in p anti-p collisions at s**(1/2) = 1.96 TeV
None
Date:
January 1, 2005
Creator:
Acosta, D.; Adelman, J.; Affolder, T.; Akimoto, T.; Albrow, M. G.; Ambrose, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the W+ W- production cross section in p anti-p collisions at s**(1/2) =1.96-TeV using dilepton events
We present a measurement of the W{sup +}W{sup -} production cross section using 184 pb{sup -1} of p{bar p} collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W{sup +}W{sup -} {yields} {ell}{sup +}{nu}{ell}{sup -}{ovr {nu}}, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0{sub -0.8}{sup +2.2} events. The resulting W{sup +}W{sup -} production cross section measurement of {sigma}(p{bar p} {yields} W{sup +}W{sup -}) = 14.6{sub -5.1}{sup +5.8}(stat){sub -3.0}{sup +1.8}(syst) {+-} 0.9(lum) pb agrees well with the Standard Model expectation.
Date:
January 1, 2005
Creator:
Acosta, D.; Adelman, J.; Affolder, T.; Akimoto, T.; Albrow, M. G.; Ambrose, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for ZZ and ZW production in p anti-p collisions at s**(1/2) = 1.96-TeV
None
Date:
January 1, 2005
Creator:
Acosta, D.; Adelman, J.; Affolder, T.; Akimoto, T.; Albrow, M. G.; Ambrose, D. et al.
Object Type:
Article
System:
The UNT Digital Library
K0(s) and Lambda0 production studies in p anti-p collisions at s**(1/2) = 1800 and 630-GeV
The authors present a study of the production of K{sub s}{sup 0} and {Lambda}{sup 0} in inelastic p{bar p} collisions at {radical}s = 1800 and 630 GeV using data collected by the CDF experiment at the Fermilab Tevatron. Analyses of K{sub s}{sup 0} and {Lambda}{sup 0} multiplicity and transverse momentum distributions, as well as of the dependencies of the average number and (p{sub T}) of K{sub s}{sup 0} and {Lambda}{sup 0} on charged particle multiplicity are reported. Systematic comparisons are performed for the full sample of inelastic collisions, and for the low and high momentum transfer subsamples, at the two energies. The p{sub T} distributions extend above 8 GeV/c, showing a (p{sub T}) higher than previous measurements. The dependence of the mean K{sub s}{sup 0}({Lambda}{sup 0}) p{sub T} on the charged particle multiplicity for the three samples shows a behavior analogous to that of charged primary tracks.
Date:
April 1, 2005
Creator:
Acosta, D.; Affolder, Anthony A.; Albrow, M. G.; Ambrose, D.; Amidei, D.; Anikeev, K. et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the azimuthal angle distribution of leptons from W boson decays as a function of the W transverse momentum in p anti-p collisions at s**(1/2) = 1.8-TeV
We present the first measurement of the A{sub 2} and A{sub 3} angular coefficients of the W boson produced in proton-antiproton collisions. We study W {yields} ev{sub e} and W {yields} {mu}{nu}{sub {mu}} candidate events produced in association with at least one jet at CDF, during Run Ia and Run Ib of the Tevatron at {radical}s = 1.8 TeV. The corresponding integrated luminosity was 110 pb{sup -1}. The jet balances the transverse momentum of the W and introduces QCD effects in W boson production. The extraction of the angular coefficients is achieved through the direct measurement of the azimuthal angle of the charged lepton in the Collins-Soper rest-frame of the W boson. The angular coefficients are measured as a function of the transverse momentum of the W boson. The electron, muon, and combined results are in good agreement with the Standard Model prediction, up to order {alpha}{sub s}{sup 2} in QCD.
Date:
April 1, 2005
Creator:
Acosta, D.; Affolder, Anthony A.; Albrow, M. G.; Ambrose, D.; Amidei, D.; Anikeev, K. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for Higgs bosons decaying into b anti-b and produced in association with a vector boson in p anti-p collisions at 1.8-TeV
The authors present a new search for H{sup 0}V production, where H{sup 0} is a scalar Higgs boson decaying into b{bar b} with branching ratio {beta}, and V is a Z{sup 0} boson decaying into e{sup +}e{sup -}, {mu}{sup +}{mu}{sup -}, or {nu}{bar {nu}}. This search is then combined with previous searches for H{sup 0}V where V is a W{sup {+-}} boson or a hadronically decaying Z{sup 0}. The data sample consists of 106 {+-} 4 pb{sup -1} or p{bar p} collisions at {radical}s = 1.8 TeV accumulated by the Collider Detector at Fermilab. Observing no evidence of a signal, they set 95% Bayesian credibility level upper limits on {sigma}(p{bar p} {yields} H{sup 0}V) x {beta}. For H{sup 0} masses of 90, 110 and 130 GeV/c{sup 2}, the limits are 7.8, 7.2, and 6.6 pb respectively.
Date:
March 1, 2005
Creator:
Acosta, D.; Affolder, Anthony A.; Albrow, M. G.; Ambrose, D.; Amidei, D.; Anikeev, K. et al.
Object Type:
Article
System:
The UNT Digital Library
A Search for supersymmetric Higgs bosons in the di-tau decay mode in p anti-p collisions at s**(1/2) = 1.8-TeV
A search for direct production of Higgs bosons in the di-tau decay mode is performed with 86.3 {+-} 3.5 pb{sup -1} of data collected with the Collider Detector at Fermilab during the 1994-1995 data taking period of the Tevatron. We search for events where one tau decays to an electron plus neutrinos and the other tau decays hadronically. We perform a counting experiment and set limits on the cross section for supersymmetric Higgs boson production where tan {beta} is large and m{sub A} is small. For a benchmark parameter space point where m{sub A{sup 0}} = 100 GeV/c{sup 2} and tan {beta} = 50, we limit the production cross section multiplied by the branching ratio to be less than 77.9 pb at the 95% confidence level compared to theoretically predicted value of 11.0 pb. This is the first search for Higgs bosons decaying to tau pairs at a hadron collider.
Date:
June 1, 2005
Creator:
Acosta, D.; Affolder, Anthony A.; Albrow, M. G.; Ambrose, D.; Amidei, D.; Anikeev, K. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for W and Z bosons in the reaction anti-p p ---> 2 jets + gamma at s**(1/2) = 1.8-TeV
The authors present a study of the dijet invariant mass distribution for the reaction {bar p}p {yields} 2 jets+{gamma} + X, at a center of mass energy of 1.8 TeV, using data collected by the CDF experiment. They compare the data to predictions for the production of a photon with two jets, together with the resonant processes {bar p}p {yields} W/Z + {gamma} + X, in which the W and Z bosons decay hadronically. A fit is made to the dijet invariant mass distribution combining the non-resonant background and resonant processes. They use the result to establish a limit for the inclusive production cross section of W/Z + {gamma} with hadronic decay of the W and Z bosons.
Date:
July 1, 2005
Creator:
Acosta, D.; Affolder, Anthony A.; Albrow, M. G.; Ambrose, D.; Amidei, D.; Anikeev, K. et al.
Object Type:
Article
System:
The UNT Digital Library
Rhombohedral AlPt films formed by self-propagating, high temperature synthesis.
High-purity AlPt thin films prepared by self-propagating, high temperature combustion synthesis show evidence for a new rhombohedral phase. Sputter deposited Al/Pt multilayers of various designs are reacted at different rates in air and in vacuum, and each form a new trigonal/hexagonal aluminide phase with unit cell parameters a = 15.571(8) {angstrom}, c = 5.304(1) {angstrom}, space group R-3 (148), and Z, the number of formula units within a unit cell, = 39. The lattice is isostructural to that of the AlPd R-3 lattice as reported by Matkovic and Schubert (Matkovic, 1977). Reacted films have a random in-plane crystallographic texture, a modest out-of-plane (001) texture, and equiaxed grains with dimensions on the order of film thickness.
Date:
November 1, 2005
Creator:
Adams, David Price; Rodriguez, Mark Andrew & Kotula, Paul Gabriel
Object Type:
Report
System:
The UNT Digital Library
First observations of separated atmospheric nu(mu) and anti-nu(mu) events in the MINOS detector
None
Date:
December 1, 2005
Creator:
Adamson, P.; Alexopoulos, T.; Allison, W. W. M.; Alner, G. J.; Anderson, K.; Andreopoulos, C. et al.
Object Type:
Article
System:
The UNT Digital Library
Operational performance of a bunch by bunch digital damper in the Fermilab Main Injector
We have implemented a transverse and longitudinal bunch by bunch digital damper system in the Fermilab Main Injector, using a single digital board for all 3 coordinates. The system has been commissioned over the last year, and is now operational in all MI cycles, damping beam bunched at both 53MHz and 2.5MHz. We describe the performance of this system both for collider operations and high-intensity running for the NuMI project, operating with a full ring and sometimes with only a few buckets populated.
Date:
May 1, 2005
Creator:
Adamson, P.; Ashmanskas, W. J.; Foster, G. W.; Hansen, S.; Marchionni, A.; Nicklaus, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Ensemble Atmospheric Modelingfor Emergency Response in Support of Federal Consequence Assessments
None
Date:
December 1, 2005
Creator:
Addis, Robert P. & Merrick, John L., Jr.
Object Type:
Article
System:
The UNT Digital Library
Performance and Reliability of a 1-kW Amorphous Silicon Photovoltaic Roofing System
The National Renewable Energy Laboratory (NREL) has been monitoring the performance of a 1- kWAC United Solar Systems Corporation (USSC) roofing system over the 6-year period from October 1998 to September 2004. This paper will investigate the performance and reliability of this system. The annual degradation and seasonal fluctuation of the system's power output are calculated using the PVUSA power rating regression model. The system performance is also examined using the additional performance parameters of yield, reference yield, and performance ratio, which allows for a somewhat less complicated data collection and analysis. The data indicate that the system has exhibited stable performance over time, with an overall degradation rate comparable to that found in crystalline silicon systems.
Date:
February 1, 2005
Creator:
Adelstein, J. & Sekulic, B.
Object Type:
Article
System:
The UNT Digital Library
Small PV Systems Performance Evaluation at NREL's Outdoor Test Facility Using the PVUSA Power Rating Method
The PV Systems Performance and Reliability R & D group currently has seven grid-tied 1-2 kilowatt PV systems deployed at NREL's Outdoor Test Facility (OTF) and two 6 kilowatt systems mounted on the roof of NREL's Solar Energy Research Facility (SERF). The systems, which employ several PV module technologies including crystalline silicon (c-Si), amorphous silicon (a-Si), cadmium telluride (CdTe), and copper indium diselenide (CIS), are being monitored to determine the long-term performance and reliability of the modules and arrays under actual field conditions. The length of observation ranges from 2 months for our newest system to 11 years for our oldest systems. The annual degradation and seasonal fluctuation of the systems' power output are calculated using the PV for Utility-Scale Applications (PVUSA) power rating regression model.
Date:
November 1, 2005
Creator:
Adelstein, J. & Sekulic, W.
Object Type:
Article
System:
The UNT Digital Library
Nanoscale Structural Engineering of Ferroelectric Polymers. Final Report for July 2001-June 2005
This final report describes the interaction between multilavered films of polymer ferroelectrics, in our case the copolymers of PVDF formed with TrFE. Langmuir Blodgett deposition of these films allows the deposition of thin, uniform, highly crystalline films. Two type of multilayer stacks are made and characterized. The first consists of multilayer stacks of the copolymer films with 2 different TrFE contents-50% and 20%. By varying the period of the multilayer stacks we see evidence of interaction at short length scales, evidenced in the thermodynamic transition temperatures of the multilayer films. The second set consists of a P(VDF - TrFE) film sandwiched between two Cobalt electrodes. In these we see evidence of a large magnetoelectric coupling.
Date:
December 1, 2005
Creator:
Adenwalla, S.
Object Type:
Report
System:
The UNT Digital Library
Calibration of the surface array of the Pierre Auger Observatory
The ground array of the Pierre Auger Observatory consists of 1600 water Cherenkov detectors, deployed over 3000 km{sup 2}. The remoteness and large number of detectors required a simple, automatic remote calibration procedure. The primary physics calibration is based on the average charge deposited by a vertical and central throughgoing muon, determined with good precision at the detector via a novel rate-based technique and later with higher precision via charge histograms. This value is named the vertical-equivalent muon (VEM). The VEM and the other parameters needed to maintain this calibration over the full energy range and to assess the quality of the detector are measured every minute. This allows an accurate determination of the energy deposited in each detector when an atmospheric cosmic ray shower occurs.
Date:
August 1, 2005
Creator:
Aglietta, M.; Allison, P. S.; Arneodo, F.; Barnhill, D.; Bauleo, P.; Beatty, J. J. et al.
Object Type:
Article
System:
The UNT Digital Library
Response of the Pierre Auger Observatory water Cherenkov detectors to muons
Two test detectors similar to the Pierre Auger Observatory Water Cherenkov Detectors have been installed at the Observatory site and at the Institut de Physique Nucleaire d'Orsay. The signals from the tanks are read out using three 9'' photomultipliers and analyzed by both a digital oscilloscope with high sampling frequency and the Auger surface detector electronics. Additionally, the detectors are equipped with plastic scintillators serving as muon telescopes. The trigger is provided either by the muon telescope or by the coincidence of the three PMTs. The scintillators are movable allowing the study of the detector response to atmospheric muons arriving with different incident angles. In this paper, the results of measurements for vertical and inclined background muons are presented. These results are compared to simulations and important calibration parameters are extracted. The influence of the direct light detected by the PMTs, particularly important for inclined showers, is discussed.
Date:
July 1, 2005
Creator:
Aglietta, M.; Allison, P.; Andres, E. C.; Arneodo, F.; Bertou, Xavier; Bonifazi, C. et al.
Object Type:
Article
System:
The UNT Digital Library
IMPROVED TUBULARS FOR BETTER ECONOMICS IN DEEP GAS WELL DRILLING USING MICROWAVE TECHNOLOGY
The main objective of the research program has been to improve the rate-of-penetration in deep hostile environments by improving the life cycle and performance of coiled-tubing, an important component of a deep well drilling system for oil and gas exploration, by utilizing the latest developments in the microwave materials technology. Originally, it was proposed to accomplish this by developing an efficient and economically viable continuous microwave process to sinter continuously formed/extruded steel powder for the manufacture of seamless coiled tubing and other tubular products. However, based on the results and faced with insurmountable difficulties in the extrusion and de-waxing processes, the approach of achieving the goals of the program has been slightly changed. In the continuation proposal an approach of microwave sintering combined with Cold Isostatic Press (CIP) and joining (by induction or microwave) is adopted. This process can be developed into a semi-continuous sintering process if the CIP can produce parts fast enough to match the microwave sintering rates. Originally, the entire program was spread over three phases with the following goals: Phase I: Demonstration of the feasibility concept of continuous microwave sintering process for tubular steel products. Phase II: Design, building and testing of a prototype microwave system …
Date:
March 1, 2005
Creator:
Agrawal, Dinesh; Gigl, Paul; Dennis, Mahlon & Stanley, Roderic
Object Type:
Report
System:
The UNT Digital Library
Candidate isolated neutron stars and other optically blank x-ray fields identified from the rosat all-sky and sloan digital sky surveys
Only seven radio-quiet isolated neutron stars (INSs) emitting thermal X rays are known, a sample that has yet to definitively address such fundamental issues as the equation of state of degenerate neutron matter. We describe a selection algorithm based on a cross-correlation of the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS) that identifies X-ray error circles devoid of plausible optical counterparts to the SDSS g {approx} 22 magnitudes limit. We quantitatively characterize these error circles as optically blank; they may host INSs or other similarly exotic X-ray sources such as radio-quiet BL Lacs, obscured AGN, etc. Our search is an order of magnitude more selective than previous searches for optically blank RASS error circles, and excludes the 99.9% of error circles that contain more common X-ray-emitting subclasses. We find 11 candidates, nine of which are new. While our search is designed to find the best INS candidates and not to produce a complete list of INSs in the RASS, it is reassuring that our number of candidates is consistent with predictions from INS population models. Further X-ray observations will obtain pinpoint positions and determine whether these sources are entirely optically blank at g {approx} 22, supporting …
Date:
November 1, 2005
Creator:
Agueros, Marcel A.; Anderson, Scott F.; Margon, Bruce; Haberl, Frank; Voges, Wolfgang; Annis, James et al.
Object Type:
Article
System:
The UNT Digital Library
Supersymmetry Parameter Analysis: SPA Convention and Project
None
Date:
November 1, 2005
Creator:
Aguilar-Saavedra, J. A.; Ali, A.; Allanach, B. C.; Arnowitt, R.; Baer, H. A.; Bagger, J. A. et al.
Object Type:
Article
System:
The UNT Digital Library
Fundamentals of Natural Gas and Species Flows from Hydrate Dissociation-Applications to Safety and Sea Floor Instability
Natural gas production from the dissociation of methane hydrate in a confined reservoir by a depressurizing down-hole well was studied. The case that the well pressure was kept constant was treated and two different linearization schemes in an axisymmetric configuration were used in the analysis. For different fixed well pressures and reservoir temperatures, approximate self-similar solutions were obtained. Distributions of temperature, pressure and gas velocity field across the reservoir were evaluated. The distance of the decomposition front from the well and the natural gas production rate as functions of time were also computed. Time evolutions of the resulting profiles were presented in graphical forms and their differences with the constant well output results were studied. It was shown that the gas production rate was a sensitive function of well pressure and reservoir temperature. The sensitivity of the results to the linearization scheme used was also studied.
Date:
September 1, 2005
Creator:
Ahmadi, Goodarz
Object Type:
Report
System:
The UNT Digital Library
Recombination Lifetimes Using the RCPCD Technique: Comparison with Other Methods
The theory and operation of the resonance-coupled photoconductive decay (RCPCD) technique is described. Examples are presented of data measured on a wide variety of sample types. The RCPCD technique has been applied to a variety of wafer and thin-film materials. Using this technique, we can measure recombination lifetime over at least three decades of injection level. We can also measure relative values of minority-carrier mobility and diffusion length. By scanning the excitation wavelength, we can measure spectral response and photoconductive excitation spectra. Deep-level impurities have been detected by several variations of RCPCD.
Date:
January 1, 2005
Creator:
Ahrenkiel, R. K.; Johnston, S. W. & Dashdorj, J.
Object Type:
Article
System:
The UNT Digital Library