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A Measurement of the Semileptonic Branching Fraction of the B_s Meson

Description: We report a measurement of the inclusive semileptonic branching fraction of the B{sub s} meson using data collected with the BABAR detector in the center-of-mass energy region above the {gamma}(4S) resonance. We use the inclusive yield of {phi} mesons and the {phi} yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B{sub s} mesons relative to all B mesons as a function of center-of-mass energy. The inclusive semileptonic branching fraction of the B{sub s} meson is determined to be {Beta}(B{sub s} {yields} {ell}{nu}X) = 9.5{sub -2.0}{sup +2.5}(stat){sub -1.9}{sup +1.1}(syst)%, where {ell} indicates the average of e and {mu}.
Date: June 12, 2012
Creator: Lees, J.P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M. et al.
Partner: UNT Libraries Government Documents Department

Better HMC integrators for dynamical simulations

Description: We show how to improve the molecular dynamics step of Hybrid Monte Carlo, both by tuning the integrator using Poisson brackets measurements and by the use of force gradient integrators. We present results for moderate lattice sizes.
Date: June 1, 2010
Creator: M.A. Clark, Balint Joo, A.D. Kennedy, P.J. Silva
Partner: UNT Libraries Government Documents Department

Measurement of Single Spin Asymmetries in Semi-Inclusive Deep Inelastic Scattering Reaction n↑ ( e,e' pi{sup +}) X at Jefferson Lab

Description: What constitutes the spin of the nucleon? The answer to this question is still not completely understood. Although we know the longitudinal quark spin content very well, the data on the transverse quark spin content of the nucleon is still very sparse. Semi-inclusive Deep Inelastic Scattering (SIDIS) using transversely polarized targets provide crucial information on this aspect. The data that is currently available was taken with proton and deuteron targets. The E06-010 experiment was performed at Jefferson Lab in Hall-A to measure the single spin asymmetries in the SIDIS reaction n↑(e, e′π{sup ±}/K{sup ±})X using transversely polarized {sup 3}He target. The experiment used the continuous electron beam provided by the CEBAF accelerator with a beam energy of 5.9 GeV. Hadrons were detected in a high-resolution spectrometer in coincidence with the scattered electrons detected by the BigBite spectrometer. The kinematic coverage focuses on the valence quark region, x = 0.19 to 0.34, at Q{sup 2} = 1.77 to 2.73 (GeV/c){sup 2}. This is the first measurement on a neutron target. The data from this experiment, when combined with the world data on the proton and the deuteron, will provide constraints on the transversity and Sivers distribution functions on both the u and d-quarks in the valence region. In this work we report on the single spin asymmetries in the SIDIS n↑(e, e′π{sup +})X reaction.
Date: June 1, 2010
Creator: Allada, Kalyan
Partner: UNT Libraries Government Documents Department

How well do we know the neutron structure function?

Description: We present a detailed analysis of the uncertainty in the neutron F{sub 2}n structure function extracted from inclusive deuteron and proton deep-inelastic scattering data. The analysis includes experimental uncertainties as well as uncertainties associated with the deuteron wave function, nuclear smearing, and nucleon off-shell corrections. Consistently accounting for the Q{sup 2} dependence of the data and calculations, and restricting the nuclear corrections to microscopic models of the deuteron, we find significantly smaller uncertainty in the extracted F{sub 2}n/F{sub 2}p ratio than in previous analyses. In addition to yielding an improved extraction of the neutron structure function, this analysis also provides an important baseline that will allow future, model-independent extractions of neutron structure to be used to examine nuclear medium effects in the the deuteron.
Date: June 1, 2012
Creator: J. Arrington, J. G. Rubin, W. Melnitchouk
Partner: UNT Libraries Government Documents Department

The Electromagnetic Self-Energy Contribution to M_p - M_n and the Isovector Nucleon Magnetic Polarizability

Description: We update the determination of the isovector nucleon electromagnetic self-energy, valid to leading order in QED. A technical oversight in the literature concerning the elastic contribution to Cottingham's formula is corrected and modern knowledge of the structure functions is used to precisely determine the inelastic contribution. We find {delta}M{sub p-n}{sup {gamma}} = 1.30(03)(47) MeV. The largest uncertainty arises from a subtraction term required in the dispersive analysis, which can be related to the isovector magnetic polarizability. With plausible model assumptions, we can combine our calculation with additional input from lattice QCD to constrain this polarizability as: {beta}{sub p-n} = -0.87(85) x 10{sup -4} fm{sup 3}.
Date: June 1, 2012
Creator: Andre Walker-Loud, Carl E. Carlson, Gerald A. Miller
Partner: UNT Libraries Government Documents Department

Electroproduction de pions neutres dans le Hall A au Jefferson Laboratory

Description: The past decade has seen a strong evolution of the study of the hadron structure through exclusive processes, allowing to access to a more complete description of this structure. Exclusive processes include DVCS (Deeply Virtual Compton Scattering) as well as hard exclusive meson production. This document is particularly focussed on the latter, and more particularly on exclusive neutral pion production. In this thesis is described the analysis of triple coincidence events H(e, e'{gamma}{gamma})X, which were a consequent by-product of the DVCS experiment which occured during Fall 2004 at Jefferson Lab Hall A, to extract the ep {yields} ep{pi}{sup 0} cross section. This cross section has been measured at two values of four-momentum transfer Q{sup 2} = 1.9 GeV{sup 2} and Q{sup 2} = 2.3 GeV{sup 2}. The statistical precision for these measurements is achieved at better than 5 %. The kinematic range allows to study the evolution of the extracted cross section as a function of Q{sup 2} and W. Results are be confronted with Regge inspired calculations and Generalized (GPD) predictions. An intepretation of our data within the framework of semi-inclusive deep inelastic scattering is also discussed.
Date: June 1, 2010
Creator: Fuchey, Eric
Partner: UNT Libraries Government Documents Department

Contributions From yZ Box Diagrams to Parity Violating Elastic e-p Scattering

Description: Parity-violating (PV) elastic electron-proton scattering measures Q-weak for the proton, Q{sub W}{sup p}. To extract Q{sub W}{sup p} from data, all radiative corrections must be well-known. Recently, disagreement on the {gamma}Z box contribution to Q{sub W}{sup p} has prompted the need for further analysis of this term. Here, we support one choice of a debated factor, go beyond the previously assumed equality of electromagnetic and {gamma}Z structure functions, and find an analytic result for one of the {gamma}Z box integrals. Our numerical evaluation of the {gamma}Z box is in agreement within errors with previous reports, albeit somewhat larger in central value, and is within the uncertainty requirements of current experiments.
Date: June 1, 2011
Creator: Benjamin Rislow, Carl Carlson
Partner: UNT Libraries Government Documents Department

Calculation of the heavy-hadron axial couplings g1, g2, and g3 using lattice QCD

Description: In a recent paper [arXiv:1109.2480] we have reported on a lattice QCD calculation of the heavy-hadron axial couplings g{sub 1}, g{sub 2}, and g{sub 3}. These quantities are low-energy constants of heavy-hadron chiral perturbation theory (HH{chi}PT) and are related to the B*B{pi}, {Sigma}{sub b}*{Sigma}{sub b}{pi}, and {Sigma}{sub b}{sup (*)}{Lambda}{sub b}{pi} couplings. In the following, we discuss important details of the calculation and give further results. To determine the axial couplings, we explicitly match the matrix elements of the axial current in QCD with the corresponding matrix elements in HH{chi}PT. We construct the ratios of correlation functions used to calculate the matrix elements in lattice QCD, and study the contributions from excited states. We present the complete numerical results and discuss the data analysis in depth. In particular, we demonstrate the convergence of SU(4|2) HH{chi}PT for the axial current matrix elements at pion masses up to about 400 MeV and show the impact of the nonanalytic loop contributions. Finally, we present additional predictions for strong and radiative decay widths of charm and bottom baryons.
Date: June 1, 2012
Creator: Will Detmold, David Lin, Stefan Meinel
Partner: UNT Libraries Government Documents Department

Final Year Project Report

Description: In the last years of this eighteen-year grant project, the research efforts have focused mostly on the study of off-shell representations of supersymmetry, both on the worldline and on the world- sheet, i.e., both in supersymmetric quantum mechanics and in supersymmetric field theory in 1+1-dimensional spacetime.
Date: June 20, 2013
Creator: Hubsch, Tristan
Partner: UNT Libraries Government Documents Department

Lattice QCD in Background Fields

Description: Electromagnetic properties of hadrons can be computed by lattice simulations of QCD in background fields. We demonstrate new techniques for the investigation of charged hadron properties in electric fields. Our current calculations employ large electric fields, motivating us to analyze chiral dynamics in strong QED backgrounds, and subsequently uncover surprising non-perturbative effects present at finite volume.
Date: June 1, 2009
Creator: William Detmold, Brian Tiburzi, Andre Walker-Loud
Partner: UNT Libraries Government Documents Department

Leading order hadronic contribution to g-2 from twisted mass QCD

Description: We calculate the leading order hadronic contribution to the muon anomalous magnetic moment using twisted mass lattice QCD. The pion masses range from 330 MeV to 650 MeV. We use two lattice spacings, a=0.079 fm and 0.063 fm, to study lattice artifacts. Finite-size effects are studied for two values of the pion mass, and we calculate the disconnected contributions for four ensembles. Particular attention is paid to the dominant contributions of the vector mesons, both phenomenologically and from our lattice calculation.
Date: June 1, 2010
Creator: Dru B Renner, Xu Feng, Karl Jansen, Marcus Petschlies
Partner: UNT Libraries Government Documents Department

Excited-state spectroscopy of triply-bottom baryons from lattice QCD

Description: The spectrum of baryons containing three b quarks is calculated in nonperturbative QCD, using the lattice regularization. The energies of ten excited bbb states with J{sup P} = 1/2{sup +}, 3/2{sup +}, 5/2{sup +}, 7/2{sup +}, 1/2{sup -}, and 3/2{sup -} are determined with high precision. A domain-wall action is used for the up-, down- and strange quarks, and the bottom quarks are implemented with NRQCD. The computations are done at lattice spacings of a {approx} 0.11 fm and a {approx} 0.08 fm, and the results demonstrate the improvement of rotational symmetry as a is reduced. A large lattice volume of (2.7 fm){sup 3} is used, and extrapolations of the bbb spectrum to realistic values of the light sea-quark masses are performed. All spin-dependent energy splittings are resolved with total uncertainties of order 1 MeV, and the dependence of these splittings on the couplings in the NRQCD action is analyzed.
Date: June 1, 2012
Creator: Meinel, Stefan
Partner: UNT Libraries Government Documents Department

Nucleon Magnetic Moments and Electric Polarizabilities

Description: Electromagnetic properties of the nucleon are explored with lattice QCD using a novel technique. Focusing on background electric fields, we show how the electric polarizability can be extracted from nucleon correlation functions. A crucial step concerns addressing contributions from the magnetic moment, which affects the relativistic propagation of nucleons in electric fields. By properly handing these contributions, we can determine both magnetic moments and electric po larizabilities. Lattice results from anisotropic clover lattices are presented. Our method is not limited to the neutron; we show results for the proton as well.
Date: June 1, 2010
Creator: Detmold, W. & Walker-Loud, A.
Partner: UNT Libraries Government Documents Department

Nucleon matrix elements with Nf=2+1+1 maximally twisted fermions

Description: We present the first lattice calculation of nucleon matrix elements using four dynamical flavors. We use the Nf=2+1+1 maximally twisted mass formulation. The renormalization is performed non-perturbatively in the RI'-MOM scheme and results are given for the vector and axial vector operators with up to one-derivative. Our calculation of the average momentum of the unpolarized non-singlet parton distribution is presented and compared to our previous results obtained from the Nf=2 case.
Date: June 1, 2010
Creator: Simon Dinter, Constantia Alexandrou, Martha Constantinou, Vincent Drach, Karl Jansen, Dru Renner
Partner: UNT Libraries Government Documents Department

Nuclear physics with a medium-energy Electron-Ion Collider

Description: A polarized ep/eA collider (Electron-Ion Collider, or EIC) with variable center-of-mass energy {radical}s {approx} 20-70 GeV and a luminosity {approx}10{sup 34} cm{sup -2} s{sup -1} would be uniquely suited to address several outstanding questions of Quantum Chromodynamics (QCD) and the microscopic structure of hadrons and nuclei: (i) the three-dimensional structure of the nucleon in QCD (sea quark and gluon spatial distributions, orbital motion, polarization, correlations); (ii) the fundamental color fields in nuclei (nuclear parton densities, shadowing, coherence effects, color transparency); (iii) the conversion of color charge to hadrons (fragmentation, parton propagation through matter, in-medium jets). We briefly review the conceptual aspects of these questions and the measurements that would address them, emphasizing the qualitatively new information that could be obtained with the collider. Such a medium-energy EIC could be realized at Jefferson Lab after the 12 GeV Upgrade (MEIC), or at Brookhaven National Lab as the low-energy stage of eRHIC.
Date: June 1, 2012
Creator: A. Accardi, V. Guzey, A. Prokudin, C. Weiss
Partner: UNT Libraries Government Documents Department

Nucleon, Delta and Omega excited state spectra at three pion mass values

Description: The energies of the excited states of the Nucleon, Delta and Omega are computed in lattice QCD, using two light quarks and one strange quark on anisotropic lattices. The calculations are performed at three values of the pion mass: 392(4), 438(3) and 521(3) MeV. We employ the variational method with a basis of about ten interpolating operators enabling six energies to be distinguished clearly in each irreducible representation of the octahedral group. We compare our calculations of nucleon excited states with the low-lying experimental spectrum. There is reasonable agreement for the pattern of states.
Date: June 1, 2010
Creator: John Bulava, Robert G. Edwards, Balint Joo, David G. Richards, Eric Engelson, Huey-Wen Lin, Colin Morningstar, Stephen J. Wallace
Partner: UNT Libraries Government Documents Department

Calculation of TMD Evolution for Transverse Single Spin Asymmetry Measurements

Description: In this letter, we show that it is necessary to include the full treatment of QCD evolution of Transverse Momentum Dependent parton densities to explain discrepancies between HERMES data and recent COMPASS data on a proton target for the Sivers transverse single spin asymmetry in Semi-Inclusive Deep Inelastic Scattering (SIDIS). Calculations based on existing fits to TMDs in SIDIS, and including evolution within the Collins-Soper-Sterman with properly defined TMD PDFs are shown to provide a good explanation for the discrepancy. The non-perturbative input needed for the implementation of evolution is taken from earlier analyses of unpolarized Drell-Yan (DY) scattering at high energy. Its success in describing the Sivers function in SIDIS data at much lower energies is strong evidence in support of the unifying aspect of the QCD TMD-factorization formalism.
Date: June 1, 2012
Creator: Mert Aybat, Ted Rogers, Alexey Prokudin
Partner: UNT Libraries Government Documents Department

Naive time-reversal odd phenomena in semi-inclusive deep-inelastic scattering from light-cone constituent quark models

Description: We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naively time-reversal odd transverse-momentum dependent parton distribution functions from the light-cone constituent quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.
Date: June 1, 2011
Creator: Barbara Pasquini, Peter Schweitzer
Partner: UNT Libraries Government Documents Department

KINETICS OF PARTICLE GROWTH IN A FLUIDIZED CALCINER

Description: Fluidized calcination involves the injection of an atomized feed solution containing dissolved solids into a bed of fluidized partioles at elevated temperatures suitable for drying and calcining. The study was conducted in a threeinch diameter fluidized column using aluminum oxide as bed material and aqueous aluminum nitrate solution as feed. Products were removed at regular intervals to maintain a constant bed weight. Particle growth was traced by adding radioactive aluminum oxide seeds of a given size to the starting bed and following their progress as they grew into successively larger sieve fractions. The effects on the growth rate of operating variables and physical properties of the feed were studied, including fluidizing air velocity, atomizing air rate, column temperature, feed concentration, feed rate, and viscosity and surface tension of the feed. For each product using screen analysis and gammacounting data a volume-surface mean diameter of the seedcontaining particles was calculated. Upon statistical analysis a linear relationship between the mean diameter of seed-containing particles and time exhibited very strong correlation, substantiating the hypothesis that particle growth was proportional to its surface area. From this linear relationship the over-all growth constant, equal to the slope, was obtained. Attrition effect of the atomizing air was found statistically to be non-significant. Normal growth far outweighed attrition and for steady-state operation other methods to produce seeds, such as jet or target attrition must be employed to balance normal growth. (auth)
Date: June 1, 1960
Creator: Lee, B. S.
Partner: UNT Libraries Government Documents Department

Study of Quasielastic 1p-shell proton Knockout in the {sup 16}O (e,e'p) reaction at Q{sup 2}=0.8 (GeV/c){sup 2}

Description: Coincidence cross sections and the structure functions R{sub L+TT},#2; R{sub T} and R{sub LT} have been obtained for the quasielastic #2;#3;{sup 16}O(#7;e,#2; e'p)#8; reaction with the proton knocked out from the #2;1p{sub 1/2}#2;#2;#4; and #2;1p{sub 3/2}#5;#2;#4; states in perpendicular kinematics. The nominal energy transfer #3;{omega} was 439#11; MeV#4; the nominal Q{sup 2}#4; was 0.8 (#7;GeV/#14;c){sup 2}#8;#4; and the kinetic energy of knocked-#15;out proton was 427#3;#16; MeV. The data was taken in Hall A#4; Je#17;erson Laboratory#4; using two high resolution spectrometers to detect electrons and protons respectively. Nominal beam energies 845#18; MeV#4;, #2;#19;1645#18; MeV#4; and #3;2445#18; MeV were employed. For each beam energy,#4; the momentum and angle of electron arm were #6;fixed,#4; while the angle between the proton momentum and the momentum transfer {vector #4;q} was varied to map out the missing momentum. R{sub LT} was separated out to ~350 MeV#14;/c in missing momentum. R{sub L+TT} and R{sub T} were separated out to #2;#3;~280 MeV/#14;c in missing momentum. R{sub L} and R{sub T} were separated at a missing momentum of #18;#3;52.5#18; MeV/#14;c for the data taken with hadron arm along #4;{vector q}. The measured cross sections and response functions agree with both relativistic and non#15;relativistic DWIA calculations employing spectroscopic factors between #19;60-75% for 1#2;p{sub 1/2}#2;#2;#4; and 1#2;p{sub 3/2}#5;#2;#4; states. The left-#15;right asymmetry does not support the non#15;-relativistic DWIA calculation using the Weyl gauge. Also#4; the left-#15;right asymmetry measurement favors the relativistic calculation. This thesis describes the details of the experimental setup#4;, the calibration of the spectrometers,#4; the techniques used in the data analysis to derive the fi#6;nal cross sec#15;tions as well as the response functions#4; and the comparison of the results with the theoretical calculations.
Date: June 1, 1999
Creator: Gao, Juncai
Partner: UNT Libraries Government Documents Department

Baryon number and strangeness: signals of a deconfinedantecedent

Description: The correlation between baryon number and strangeness is used to discern the nature of the deconfined matter produced at vanishing chemical potential in high-energy nuclear collisions at the BNL RHIC. Comparisons of results of various phenomenological models with correlations extracted from lattice QCD calculations suggest that a quasi-particle picture applies. At finite baryon densities, such as those encountered at the CERN SPS, it is demonstrated that the presence of a first-order phase transition and the accompanying development of spinodal decomposition would significantly enhance the number of strangeness carriers and the associated fluctuations.
Date: June 29, 2005
Creator: Majumder, A.; Koch, V. & Randrup, J.
Partner: UNT Libraries Government Documents Department

Analytical Modeling of Wave Generation by the Borehole OrbitalVibrator Source

Description: The orbital vibrator source (a fluid-coupled shear wave source) has many unique properties that are useful for cross-well, single-well, and borehole-to-surface imaging of both P- (compressional)and S-(shear) wave velocities of reservoir rocks. To this day, however, no standard models for this source have been established, and the mechanism of wave generation and the characteristics of wave field around the source are not well understood yet. In this article, we develop both two and three-dimensional analytical models of the orbital vibrator source, which allow us to examine the source characteristics such as radiation patterns, frequency-dependence of the wave energy, and guided-wave generation. These models are developed in the frequency-wave number domain using the partial wave expansion of the wavefield within and outside the borehole. The results show that the developed models successfully reproduce many characteristics of orbital vibrator source that have been observed in the field, including formation property-dependent vibrator amplitudes, uniform isotropic shear wave radiation pattern, and small tube-wave generation.
Date: June 28, 2004
Creator: Nakagawa, Seiji & Daley, Thomas M.
Partner: UNT Libraries Government Documents Department