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The Feynman-Schwinger (World Line) Representation in Perturbative QCD

Description: The proper time path integral representation is derived explicitly for an arbitrary $n$-point amplitude in QCD. In the standard perturbation theory the formalism allows to sum up the leading subseries, e.g. yielding double-logarithm Sudakov asymptotics for form factors. Correspondence with the standard perturbation theory is established and connection to the Bern-Kosower-Strassler method is illustrated.
Date: December 1, 2001
Creator: Simonov, Yu A. & Tjon, J.A.
Partner: UNT Libraries Government Documents Department

Applications of magnetized plasma to particle acceleration

Description: Magnetized plasma can be used as an accelerating structure capable of supporting large amplitude longitudinal fields which are externally driven by a high-frequency microwave source. Such structures can be used at very high frequencies (hundreds of gigahertz), placing them in the intermediate region between conventional (metallic) accelerators, and laser-driven plasma accelerators. They review two magnetic field configurations with respect to the direction of the particle beam propagation: (1) parallel magnetic field plus a helical undulator, and (2) perpendicular magnetic field. In the first configuration, plasma exhibits electromagnetically induced transparency (EIT) at the cyclotron frequency if the plasma frequency is equal to the electron cyclotron frequency. The second configuration corresponds to the inverse Cherenkov effect in magnetized plasma. In both cases, the group velocity of the accelerating plasma wave can be made very small, so that the incident electromagnetic wave is strongly compressed, resulting in the high accelerating gradient.
Date: December 12, 2002
Creator: Shvets, Gennady; Wurtele, Jonathan S. & Hur, Min-Sup
Partner: UNT Libraries Government Documents Department

Resonance Contributions to {eta} Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model

Description: The contributions of the resonances D{sub 13}(1520), S{sub 11}(1535), S{sub 11}(1650), D{sub 15}(1675), F{sub 15}(1680), D{sub 13}(1700), P{sub 11}(1710), P{sub 13}(1720) to {gamma}p {yields} {eta}p are found from the data on cross sections, beam and target asymmetries using two approaches: fixed-t dispersion relations and an isobar model. Utilization of the two approaches and comparison of the results obtained with different parametrizations of the resonance contributions allowed us to make conclusions about the model-dependence of these contributions. We conclude that the results for the contributions of the resonances D{sub 13}(1520), S{sub 11}(1535), F{sub 15}(1680) to corresponding multipole amplitudes are stable. With this the results for D{sub 13}(1520) and F{sub 15}(1680), combined with their PDG photoexcitation helicity amplitudes, allowed us to find the branching ratios Br (D{sub 13}(1520) {yields} {eta}N) = 0.05 {+-} 0.02%, Br (F{sub 15}(1680) {yields} {eta} N) = 0.16 {+-} 0.04% which have significantly better accuracy than the PDG data. The total Breit-Wigner width of the S{sub 11}(1535) is model-dependent, we have obtained {Gamma} (S{sub 11}(1520)) = 142 MeV and 195 MeV using dispersion relations and the isobar model, respectively. The results for the S{sub 11}(1650), D{sub 15}(1675), P{sub 11}(1710), P{sub 13}(1720) are model dependent, only the signs and orders of magnitude of their contributions to multipole amplitudes are determined. The results for the D{sub 13}(1700) are strongly model-dependent.
Date: December 1, 2003
Creator: Aznauryan, Inna
Partner: UNT Libraries Government Documents Department

Quantum non-locality in a two-slit interferometer for short-lived particles

Description: We describe a new test of quantum nonlocality, using an interferometer for short-lived particles. The separation is large compared with the particle lifetimes. This interferometer is realized by vector meson production in distant heavy ion collisions. The mesons decay before waves from the two sources (ions) can overlap, so interference is only possible among the decay products. The post-decay wave function must retain amplitudes for all possible decays. The decay products are spatially separated, necessitating a non-local wave function. The interference is measurable by summing the product momenta. Alternately, the products positions could be observed, allowing new tests of the EPR paradox.
Date: December 1, 2001
Creator: Klein, Spencer R. & Nystrand, Joakim
Partner: UNT Libraries Government Documents Department

The photon polarization in b -> X gamma in the standard model

Description: The standard model prediction for the {bar B}{sup 0} {yields} X{sub s,d}{gamma} decay amplitude with a right-handed photon is believed to be tiny, suppressed by m{sub s,d}/m{sub b}, compared to the amplitude with a left-handed photon. We show that this suppression is fictitious: in inclusive decays, the ratio of these two amplitudes is only suppressed by g{sub s}/(4{pi}), and in exclusive decays by {Lambda}{sub QCD}/m{sub b}. The suppression is not stronger in {bar B}{sup 0} {yields} X{sub d}{gamma} decays than it is in {bar B}{sup 0} {yields} X{sub s}{gamma}. We estimate that the time dependent CP asymmetries in B {yields} K*{gamma}, {rho}{gamma}, K{sub S}{pi}{sup 0}{gamma}, and {pi}{sup +}{pi}{sup -} {gamma} are of order 0.1 and that they have significant uncertainties.
Date: December 8, 2004
Creator: Grinstein, Benjamin; Grossman, Yuval; Ligeti, Zoltan & Pirjol, Dan
Partner: UNT Libraries Government Documents Department

Upper limits on the strength of periodic gravitational waves from PSR J1939+2134

Description: The first science run of the LIGO and GEO gravitational wave detectors presented the opportunity to test methods of searching for gravitational waves from known pulsars. Here we present new direct upper limits on the strength of waves from the pulsar PSR J1939+2134 using two independent analysis methods, one in the frequency domain using frequentist statistics and one in the time domain using Bayesian inference. Both methods show that the strain amplitude at Earth from this pulsar is less than a few times 10{sup -22}.
Date: December 11, 2003
Creator: al., B. Allen et
Partner: UNT Libraries Government Documents Department

Synchrotron radiation from electron beams in plasma focusing channels

Description: Spontaneous radiation emitted from relativistic electrons undergoing betatron motion in a plasma focusing channel is analyzed and application to plasma wakefield accelerator experiments and to the ion channel laser (ICL) are discussed. Important similarities and differences between a free electron laser (FEL) and an ICL are delineated. It is shown that the frequency of spontaneous radiation is a strong function of the betatron strength parameter alpha-beta, which plays a similar role to that of the wiggler strength parameter in a conventional FEL. For alpha-beta > 1, radiation is emitted in numerous harmonics. Furthermore, alpha-beta is proportional to the amplitude of the betatron orbit, which varies for every electron in the beam. The radiation spectrum emitted from an electron beam is calculated by averaging the single electron spectrum over the electron distribution. This leads to a frequency broadening of the radiation spectrum, which places serious limits on the possibility of realizing an ICL.
Date: December 6, 2001
Creator: Esarey, E.; Shadwick, B.A.; Catravas, P. & Leemans, W.P.
Partner: UNT Libraries Government Documents Department

Measurement of Beam-Spin Asymmetries for Deep Inelastic pi{sup +} Electroproduction

Description: We report the first evidence for a non-zero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic region. Data have been obtained using a polarized electron beam of 4.3 GeV and with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). The amplitude of the sin phi modulation increases with the momentum of the pion relative to the virtual photon, z, with an average amplitude of 0.038+/-0.005+/-0.003 for 0.5<z<0.8 range.
Date: December 1, 2002
Creator: Avakian, H.; Burkert, Volker D.; Elouadrhiri, Latifa & al., et.
Partner: UNT Libraries Government Documents Department

Measurement of CP-Violating Asymmetries In Neutral B Meson Decays Into Three Kaons

Description: The Standard Model (SM) of particle physics successfully describes all of the observed interactions of the fundamental particles (with the exception of non-zero neutrino mass). Despite this enormous success, the SM is widely viewed as an incomplete theory. For example, the size of the asymmetry between matter and antimatter is not nearly large enough to account for the abundance of matter observed throughout the universe. It is thus believed that as-yet-unknown physical phenomena must exist that introduce new asymmetries between matter and antimatter. In this thesis, by studying decays that happen only rarely in the SM, we make measurements of asymmetries between matter and antimatter that are potentially sensitive to the existence of processes beyond the SM. At the PEP-II asymmetric-energy B Factory at SLAC, electrons and positrons are collided at the {Upsilon}(4S) resonance to create pairs of B mesons. The BABAR detector is used to measure the subsequent decay products. Using 383 million {Upsilon}(4S) {yields} B{bar B} decays, we study the decay B{sup 0} {yields} K{sup +}K{sup -}K{sup 0}. In the SM, this decay is dominated by loop amplitudes. Asymmetries between matter and antimatter (CP asymmetries) are extracted by measuring the time-dependence of the complex amplitudes describing the B{sup 0} and {bar B}{sup 0} decays as functions of their kinematics. The interference between decays with and without the mixing of neutral B mesons allows for the measurement of the angle {beta}{sub eff}, which is a measure of CP violation. We also measure the direct CP asymmetry A{sub CP}. Data samples reconstructed from three K{sup 0} modes (K{sub S}{sup 0} {yields} {pi}{sup +}{pi}{sup -}, K{sub S}{sup 0} {yields} {pi}{sup 0}{pi}{sup 0}, and K{sub L}{sup 0}) are fit simultaneously. They find A{sub CP} = -0.015 {+-} 0.077 {+-} 0.053 and {beta}{sub eff} = 0.352 {+-} 0.076 {+-} 0.026 rad, corresponding to ...
Date: December 1, 2008
Creator: Thompson, Joshua M.
Partner: UNT Libraries Government Documents Department

Twistor String Theory and QCD

Description: The author reviews recent progress in using twistor-inspired methods to compute perturbative scattering amplitudes in gauge theory, for application to collider physics.
Date: December 8, 2005
Creator: Dixon, Lance J.
Partner: UNT Libraries Government Documents Department

Photon-Photon Collisions -- Past and Future

Description: I give a brief review of the history of photon-photon physics and a survey of its potential at future electron-positron colliders. Exclusive hadron production processes in photon-photon and electron-photon collisions provide important tests of QCD at the amplitude level, particularly as measures of hadron distribution amplitudes. There are also important high energy {gamma}{gamma} and e{gamma} tests of quantum chromodynamics, including the production of jets in photon-photon collisions, deeply virtual Compton scattering on a photon target, and leading-twist single-spin asymmetries for a photon polarized normal to a production plane. Since photons couple directly to all fundamental fields carrying the electromagnetic current including leptons, quarks, W's and supersymmetric particles, high energy {gamma}{gamma} collisions will provide a comprehensive laboratory for Higgs production and exploring virtually every aspect of the Standard Model and its extensions. High energy back-scattered laser beams will thus greatly extend the range of physics of the International Linear Collider.
Date: December 2, 2005
Creator: Brodsky, Stanley J.
Partner: UNT Libraries Government Documents Department

Measurements of the CKM Angle beta

Description: In this article I report on new and updated measurements of the CP-violating parameter {beta}({phi}{sub 1}), which is related to the phase of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix of the electroweak interaction. Over the past few years, {beta} has become the most precisely known parameter of the CKM unitarity triangle that governs the B system. The results presented here were produced by the two B Factories, BABAR and Belle, based on their most recent datasets of over 600 million B{bar B} events combined. The new world average for sin2{beta}, measured in the theoretically and experimentally cleanest charmonium modes, such as B{sup 0} {yields} J/{Psi}K{sub S}{sup 0}, is sin 2{beta} = 0.685 {+-} 0.032. In addition to these tree-level dominated decays, independent measurements of sin2{beta} are obtained from gluonic b {yields} s penguin decays, including B{sup 0} {yields} {phi}K{sub S}{sup 0}, B{sup 0} {yields} {eta}'K{sub S}{sup 0} and others. There are hints, albeit somewhat weaker than earlier this year, that these measurements tend to come out low compared to the charmonium average, giving rise to the tantalizing possibility that New Physics amplitudes could be contributing to the corresponding loop diagrams. Clearly, more data from both experiments are needed to elucidate these intriguing differences.
Date: December 14, 2005
Creator: Bartoldus, Rainer
Partner: UNT Libraries Government Documents Department

Exclusive Two-Photon Processes in QCD

Description: Hadron pair production from two-photon annihilation plays an important role in unraveling the perturbative and non-perturbative structure of QCD, first by testing the validity and empirical applicability of leading-twist factorization theorems, second by verifying the structure of the underlying perturbative QCD subprocesses, and third, through measurements of angular distributions and ratios which are sensitive to the shape of the distribution amplitudes. In effect, photon-photon collisions provide a microscope for testing fundamental scaling laws of PQCD and for measuring distribution amplitudes. The determination of the shape and normalization of the distribution amplitude is particularly important in view of their importance in the analysis of exclusive semi-leptonic and two-body hadronic B-decays. The data from the Belle and CLEO collaborations on single and double meson production are in excellent agreement with the QCD predictions. In contrast, the normalization of the nominal leading-order predictions of PQCD for proton pair production appears to be significantly below recent Belle measurements. I also review issues relating to renormalization scale setting.
Date: December 2, 2005
Creator: Brodsky, Stanley J.
Partner: UNT Libraries Government Documents Department

Non-Standard Physics in Leptonic and Semileptonic Decays of Charmed Mesons

Description: Recent measurements of the branching fraction for D{sub s} {yields} {ell}v disagree with the Standard Model expectation, which relies on calculations of f{sub D{sub s}} from lattice QCD. This paper uses recent preliminary measurements from CLEO and a new preliminary lattice-QCD result from this conference to update the significance of the discrepancy. The 'f{sub D{sub s}} puzzle' stands now at 3.5{sigma}, with {sigma} predominantly from the statistical uncertainty of the experiments. New physics scenarios that could solve the puzzle would also lead to non-Standard amplitudes mediating the semileptonic decays D {yields} K{ell}v. This paper shows where the new amplitudes enter the differential rate and outlines where lattice QCD calculations are needed to confront recent and forthcoming measurements.
Date: December 1, 2008
Creator: Kronfeld, Andreas S.
Partner: UNT Libraries Government Documents Department

Single-Spin Asymmetries and Transversity in QCD

Description: Initial- and final-state interactions from gluon exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, as well as nuclear shadowing and antishadowing-leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. The physics of such processes thus require the understanding of QCD at the amplitude level; in particular, the physics of spin requires an understanding of the phase structure of final-state and initial-state interactions, as well as the structure of the basic wavefunctions of hadrons themselves. I also discuss transversity in exclusive channels, including how one can use single-spin asymmetries to determine the relative phases of the timelike baryon form factors, as well as the anomalous physics of the normal-normal spin-spin correlation observed in large-angle proton-proton elastic scattering. As an illustration of the utility of light-front wavefunctions, the transversity distribution of a single electron is computed, as defined from its two-particle QED quantum fluctuations.
Date: December 14, 2005
Creator: Brodsky, S.J.
Partner: UNT Libraries Government Documents Department

Search for b to u transitions in B- to [K+pi-pi0]_D K-

Description: The authors search for decays of a B meson into a neutral D meson and a kaon, with the D meson decaying into K{sup +}{pi}{sup -}{pi}{sup 0}. This final state can be reached through the b {yields} c transition B{sup -} {yields} D{sup 0}K{sup -} followed by the doubly Cabibbo-suppressed D{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0}, or the b {yields} u transition B{sup -} {yields} {bar D}{sup 0}K{sup -} followed by the Cabibbo-favored {bar D}{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0}. The interference of these two amplitudes is sensitive to the angle {gamma} of the unitarity triangle. They present preliminated results based on 226 x 10{sup 6} e{sup +}e{sup -} {yields} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector at SLAC.
Date: December 6, 2006
Creator: Aubert, B.; Barate, R.; Bona, M.; Boutigny, D.; Couderc, F.; Karyotakis, Y. et al.
Partner: UNT Libraries Government Documents Department

Far Scrape-Off Layer and Near Wall Plasma Studies in DIII-D

Description: Far scrape-off layer (SOL) plasma parameters in DIII-D depend strongly on the discharge density and confinement regime. In L-mode, cross-field transport increases with the average discharge density and elevates the far SOL density, thus increasing plasma-wall contact. Far SOL density near the low field side (LFS) of the main chamber wall also increases with decreasing plasma current and with decreasing outer wall gap. In H-mode, between edge localized modes (ELMs), plasma-wall contact is weaker than in L-mode. During ELMs plasma fluxes to the LFS wall increase to, or above the L-mode levels. A large fraction of the net cross-field fluxes is convected through the SOL by large amplitude intermittent transport events. In high density L-mode and during ELMs in H-mode, intermittent events propagate all the way to the LFS wall and may cause sputtering.
Date: December 3, 2004
Creator: Rudakov, D; Boedo, J; Moyer, R; Brooks, N; Doerner, R; Evans, T et al.
Partner: UNT Libraries Government Documents Department

Picosecond resolution soft x-ray laser plasma interferometry

Description: We describe a soft x-ray laser interferometry technique that allows two-dimensional diagnosis of plasma electron density with picosecond time resolution. It consists of the combination of a robust high throughput amplitude division interferometer and a 14.7 nm transient inversion soft x-ray laser that produces {approx} 5 ps pulses. Due to its picosecond resolution and short wavelength scalability, this technique has potential for extending the high inherent precision of soft x-ray laser interferometry to the study of very dense plasmas of significant fundamental and practical interest, such as those investigated for inertial confined fusion. Results of its use in the diagnostics of dense large scale laser-created plasmas are presented.
Date: December 1, 2003
Creator: Moon, S; Nilsen, J; Ng, A; Shlyaptsev, V; Dunn, J; Hunter, J et al.
Partner: UNT Libraries Government Documents Department

Global paths of time-periodic solutions of the Benjamin-Ono equation connecting arbitrary traveling waves

Description: We classify all bifurcations from traveling waves to non-trivial time-periodic solutions of the Benjamin-Ono equation that are predicted by linearization. We use a spectrally accurate numerical continuation method to study several paths of non-trivial solutions beyond the realm of linear theory. These paths are found to either re-connect with a different traveling wave or to blow up. In the latter case, as the bifurcation parameter approaches a critical value, the amplitude of the initial condition grows without bound and the period approaches zero. We propose a conjecture that gives the mapping from one bifurcation to its counterpart on the other side of the path of non-trivial solutions. By experimentation with data fitting, we identify the form of the exact solutions on the path connecting two traveling waves, which represents the Fourier coefficients of the solution as power sums of a finite number of particle positions whose elementary symmetric functions execute simple orbits in the complex plane (circles or epicycles). We then solve a system of algebraic equations to express the unknown constants in the new representation in terms of the mean, a spatial phase, a temporal phase, four integers (enumerating the bifurcation at each end of the path) and one additional bifurcation parameter. We also find examples of interior bifurcations from these paths of already non-trivial solutions, but we do not attempt to analyze their algebraic structure.
Date: December 11, 2008
Creator: Ambrose, David M. & Wilkening, Jon
Partner: UNT Libraries Government Documents Department

Physical limits for high ion charge states in pulsed discharges in vacuum

Description: Short-pulse, high-current discharges in vacuum were investigated with the goal to maximize the ion charge state number. In a direct extension of previous work [Appl. Phys. Lett. 92, 041502 (2008)], the role of pulse length, rate of current rise, and current amplitude was studied. For all experimental conditions, the usable (extractable) mean ion charge state could not be pushed beyond 7+. Instead, a maximum of the mean ion charge state (about 6+ to 7+ for most cathode materials) was found for a power of 2-3 MW dissipated in the discharge gap. The maximum is the result of two opposing processes that occur when the power is increased: (i) the formation of higher ion charge states, and (ii) a greater production of neutrals (both metal and non-metal), which reduces the charge state via charge exchange collisions.
Date: December 23, 2008
Creator: Yushkov, Georgy & Anders, Andre
Partner: UNT Libraries Government Documents Department

Accuracy of Analog Fiber-Optic Links in Pulsed Radiation Environments

Description: Interferometric fiber-optic links used in pulsed-power experiments are evaluated for accuracy in the presence of radiation fields which alter fiber transmission. Amplitude-modulated format (e.g., Mach-Zehnder) and phase-modulated formats are compared. Historically, studies of radiation effects on optical fibers have focused on degradation and recovery of the fibers transmission properties; such work is either in the context of survivability of fibers in catastrophic conditions or suitability of fibers installed for command and control systems within an experimental facility [1], [2]. In this work, we consider links used to transmit realtime diagnostic data, and we analyze the error introduced by radiation effects during the drive pulse. The result is increased uncertainties in key parameters required to unfold the sinusoidal transfer function. Two types of modulation are considered: amplitude modulation typical of a Mach-Zehnder (M-Z) modulator [3], and phase modulation, which offers more flexible demodulation options but relies on the spatiotemporal coherence of the light in the fiber. The M-Z link is shown schematically in Fig. 1, and the phase-modulated link is shown in Fig. 2. We present data from two experimental environments: one with intense, controlled radiation fields to simulate conditions expected at the next generation of pulsed-power facilities, and the second with radiation effects below the noise level of the recording system. In the first case, we intentionally expose three types of single-mode fiber (SMF) to ionizing radiation and study the response by simultaneously monitoring phase and amplitude of the transmitted light. The phase and amplitude effects are evidently dominated by different physical phenomena, as their recovery dynamics are markedly different; both effects, though, show similar short-term behavior during exposure, integrating the dose at the dose levels studied, from 1 to 300 kRad, over the exposure times of 50 ps and 30 ns. In the second case, we present data using ...
Date: December 1, 2007
Creator: E. K. Miller, G. S. Macrum, I. J. McKenna, et al.
Partner: UNT Libraries Government Documents Department

The Injection Laser System on the National Ignition Facility

Description: The National Ignition Facility (NIF) is currently the largest and most energetic laser system in the world. The main amplifiers are driven by the Injection Laser System comprised of the master oscillators, optical preamplifiers, temporal pulse shaping and spatial beam formatting elements and injection diagnostics. Starting with two fiber oscillators separated by up to a few angstroms, the pulse is phase modulated to suppress SBS and enhance spatial smoothing, amplified, split into 48 individual fibers, and then temporally shaped by an arbitrary waveform generator. Residual amplitude modulation induced in the preamplifiers from the phase modulation is also precompensated in the fiber portion of the system before it is injected into the 48 pre-amplifier modules (PAMs). Each of the PAMs amplifies the light from the 1 nJ fiber injection up to the multi-joule level in two stages. Between the two stages the pre-pulse is suppressed by 60 dB and the beam is spatially formatted to a square aperture with precompensation for the nonuniform gain profile of the main laser. The input sensor package is used to align the output of each PAM to the main laser and acquire energy, power, and spatial profiles for all shots. The beam transport sections split the beam from each PAM into four main laser beams (with optical isolation) forming the 192 beams of the NIF. Optical, electrical, and mechanical design considerations for long term reliability and availability will be discussed.
Date: December 13, 2006
Creator: Bowers, M; Burkhart, S; Cohen, S; Erbert, G; Heebner, J; Hermann, M et al.
Partner: UNT Libraries Government Documents Department

Expected accuracy in a measurement of the CKM angle alpha using a Dalitz plot analysis of B0 ---> rho pi decays in the BTeV project

Description: A precise measurement of the angle {alpha} in the CKM triangle is very important for a complete test of Standard Model. A theoretically clean method to extract {alpha} is provided by B{sup 0} {yields} {rho}{pi} decays. Monte Carlo simulations to obtain the BTeV reconstruction efficiency and to estimate the signal to background ratio for these decays were performed. Finally the time-dependent Dalitz plot analysis, using the isospin amplitude formalism for tre and penguin contributions, was carried out. It was shown that in one year of data taking BTeV could achieve an accuracy on {alpha} better than 5{sup o}.
Date: December 1, 2005
Creator: Shestermanov, K.E.; Vasiliev, A.N; /Serpukhov, IHEP; Butler, J.; Derevschikov, A.A.; Kasper, P. et al.
Partner: UNT Libraries Government Documents Department