Physical Sciences and Mathematics Commons^™

Target And Beam Target Spin Asymmetries In Exclusive Π+ And Π- Electroproduction With 1.6 To 5.7 Gev Electrons, P. E. Bosted, S. Careccia, G. Dodge, S. E. Kuhn, Y. Prok, M. J. Amaryan, B. Torayev, L. B. Weinstein, Z. W. Zhao, Clas Collaboration

Physics Faculty Publications

Beam-target double-spin asymmetries and target single-spin asymmetries in exclusive π⁺ and quasiexclusive π^- electroproduction were obtained from scattering of 1.6- to 5.7-GeV longitudinally polarized electrons from longitudinally polarized protons (for π⁺) and deuterons (for π^-) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic range covered is 1.1 < W < 2.6 GeV and 0.05 < Q² < 5 GeV², with good angular coverage in the forward hemisphere. The asymmetry results were divided into approximately 40 000 kinematic bins for π⁺ from free protons and 15 000 bins for π^- production from bound nucleons in the deuteron. The …

Combining Harmonic Generation And Laser Chirping To Achieve High Spectral Density In Compton Sources, Balša Terzić, Cody Reeves, Geoffrey A. Krafft

Physics Faculty Publications

Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. As a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped) and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results to demonstrate …

Comment On "Controlling The Spectral Shape Of Nonlinear Thomson Scattering With Proper Laser Chirping", Balša Terzić, Geoffrey A. Krafft

Physics Faculty Publications

Rykovanov, Geddes, Schroeder, Esarey and Leemans [Phys. Rev. Accel. Beams 19, 030701 (2016); hereafter RGSEL] have recently reported on the analytic derivation for the laser pulse frequency modulation (chirping) which controls spectrum broadening for high laser pulse intensities. We demonstrate here that their results are the same as the exact solutions reported in Terzic, Deitrick, Hofler and Krafft [Phys. Rev. Lett. 112, 074801 (2014); hereafter TDHK]. While the two papers deal with circularly and linearly polarized laser pulses, respectively, the difference in expressions for the two is just the usual factor of 1/2 present from going from circular to linear …

Ab Initio Calculation Of The Electromagnetic And Neutral Weak Response Functions Of 4He And 12C, A. Lovato, O. Benhar, J. Carlson, S. Gandolfi, Steven C. Pieper, N. Rocco, R. Schiavilla

Physics Faculty Publications

Precise measurement of neutrino oscillations, and hence the determination of their masses demands a quantitative understanding of neutrino-nucleus interactions. To this aim, two-body meson-exchange currents have to be accounted for along within realistic models of nuclear dynamics. We summarize our progresses towards the construction of a consistent framework, based on quantum Monte Carlo methods and on the spectral function approach, that can be exploited to accurately describe neutrino interactions with atomic nuclei over the broad kinematical region covered by neutrino experiments.

Connecting Physical Resonant Amplitudes And Lattice Qcd, Daniel R. Bolton, Raúl A. Briceño, David J. Wilson

Physics Faculty Publications

We present a determination of the isovector, P-wave π π scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using m_{π =} 236 MeV. The finite volume spectra are described using extensions of Ltischer's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at m_π = 140 MeV. The scattering phase shift is found to agree with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude …

First Measurement Of The Helicity Asymmetry E In Ƞ Photoproduction On The Proton, I. Senderovich, B.T. Morrison, M. Dugger, B.G. Ritchie, E. Pasyuk, R. Tucker, J. Brock, C. Carlin, C.D. Keith, D. G. Meekins, Y. Prok

Physics Faculty Publications

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the ƞ photoproduction reaction ɣp -> ηp. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich-Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the …

Hadron Resonaces From Qcd, Jozef J. Dudek

Physics Faculty Publications

I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study ππ elastic scattering, including the ρ resonance, as well as coupled-channel πK, ηK scattering. The very recent extension to the case where an external current acts is also presented, considering the reaction πγ^* → ππ, from which the unstable ρ …

Structure Constant Of Twist-2 Light Ray Operators In The Regge Limit, Ian Balitsky, Vladimir Kazakov, Evgeny Sobko

Physics Faculty Publications

We compute the normalized structure constant of three twist-2 operators in N =4 SYM in the leading Balitsky-Fadin-Kuraev-Lipatov (BFKL) approximation at any N_c . The result is applicable to other gauge theories including QCD.

High-Fidelity Simulations Of Long-Term Beam-Beam Dynamics On Gpus, B. Terzić, K. Arumugam, M. Aturban, C. Cotnoir, A. Godunov, D. Ranjan, M. Stefani, M. Zubair, F. Lin, V. Morozov, Y. Roblin, H. Zhang

Physics Faculty Publications

Future machines such as the Electron Ion Collider (MEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations typically requiring millions of turns. Until recently, most of the methods have involved using linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order. …

Analyses Of 476 Mhz And 952 Mhz Crab Cavities For Jlab Electron Ion Collider, Hyekyoung Park, A. Castilla, J. R. Delayen, S. U. De Silva, V. Morozov

Physics Faculty Publications

Center for Accelerator Science at ODU has designed, fabricated and successfully tested a crab cavity for MEIC at Jefferson Lab*. This proof of principle cavity was based on the earlier MEIC design which used 748.5 MHz RF system. The updated MEIC design** utilizes the components from PEP-II. It results in the change on the bunch repetition rate of stored beam to 476.3 MHz. The ion ring collider will eventually require 952.6 MHz crab cavity. This paper will present the analyses of crab cavities of both 476 MHz and 952 MHz options. It compares advantages and disadvantages of the options which …

First Results Of Magnetic Field Penetration Measurements Of Multilayer Sis Structures, O. B. Malyshev, L. Gurran, R. Valizadeh, S. Pattalwar, N. Pattalwar, K. D. Dumbell, A. Gurevich

Physics Faculty Publications

The performance of superconducting RF cavities made of bulk Nb is limited by a breakdown field of B_p ≈200 mT, close to the superheating field for Nb. A potentially promising solution to enhance the breakdown field of the SRF cavities beyond the intrinsic limits of Nb is a multilayer coating suggested in [1]. In the simplest case, such a multilayer may be a superconductor-insulator-superconductor (S-I-S) coating, for example, bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of another superconductor (S) which could be e.g. dirty niobium [2]. Here we report the …

"Hammer" Events, Neutrino Energies, And Nucleon-Nucleon Correlations, L. B. Weinstein, O. Hen, Eli Piasetzky

Physics Faculty Publications

Background: Accelerator-based neutrino oscillation measurements depend on observing a difference between the expected and measured rate of neutrino-nucleus interactions at different neutrino energies or different distances from the neutrino source. Neutrino-nucleus scattering cross sections are complicated and depend on the neutrino beam energy, the neutrino-nucleus interaction, and the structure of the nucleus. Knowledge of the incident neutrino energy spectrum and neutrino-detector interactions are crucial for analyzing neutrino oscillation experiments. The ArgoNeut liquid argon time projection chamber (lArTPC) observed charged-current neutrino-argon scattering events with two protons back-to-back in the final state ("hammer" events) which they associated with short-range correlated (SRC) nucleon-nucleon …

Harmonically Resonant Cavity As A Bunch-Length Monitor, B. Roberts, F. Hannon, M. M. Ali, E. Forman, J. Grames, R. Kazimi

Physics Faculty Publications

A compact, harmonically resonant cavity with fundamental resonant frequency 1497 MHz was used to evaluate the temporal characteristics of electron bunches produced by a 130 kV dc high voltage spin-polarized photoelectron source at the Continuous Electron Beam Accelerator Facility (CEBAF) photoinjector, delivered at 249.5 and 499 MHz repetition rates and ranging in width from 45 to 150 picoseconds (FWHM). A cavity antenna attached directly to a sampling oscilloscope detected the electron bunches as they passed through the cavity bore with a sensitivity of ∼1  mV/μA . The oscilloscope waveforms are a superposition of the harmonic modes excited by the beam, …

Rosenbluth Separation Of The Πᵒ Electroproduction Cross Section, M. Defurne, M. Canan, C. E. Hyde, S. Koirala, M.N.H. Rashad, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We present deeply virtual πᵒ electroproduction cross-section measurements at x_B = 0.36 and three different Q² values ranging from 1.5 to 2 GeV2, obtained from Jefferson Lab Hall A experiment E07-007. The Rosenbluth technique is used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component and, thus, is far from the asymptotic limit predicted by perturbative quantum chromodynamics. Nonetheless, an indication of a nonzero longitudinal contribution is provided by the measured interference term σ_LT. Results are compared with several models based on the leading-twist approach of …

Issues And Opportunities In Exotic Hadrons, R.A. Briceño, T. D. Cohen, S. Coito, J. J. Dudek, E. Eichten, R. E. Mitchell

Physics Faculty Publications

The last few years have been witness to a proliferation of new results concerning heavy exotic hadrons. Experimentally, many new signals have been discovered that could be pointing towards the existence of tetraquarks, pentaquarks, and other exotic configurations of quarks and gluons. Theoretically, advances in lattice field theory techniques place us at the cusp of understanding complex coupled-channel phenomena, modelling grows more sophisticated, and effective field theories are being applied to an ever greater range of situations. It is thus an opportune time to evaluate the status of the field. In the following, a series of high priority experimental and …

Photoproduction Of Λ And Σº Hyperons Using Linearly Polarized Photons, C. A. Paterson, D. G. Ireland, K. Livingston, B. Mckinnon, D. Adikaram, M. Amaryan, Y. Prok, B. Torayev

Physics Faculty Publications

Background: Measurements of polarization observables for the reactions ^→ᵧp→K+ Λ and ^→ᵧp→ K+Σ⁰ have been performed. This is part of a program of measurements designed to study the spectrum of baryon resonances in particular, and nonperturbative QCD in general.

Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits, which allow the study of strangeness in nucleon and nuclear systems. Beam-recoil observables for the ^→ᵧp→ K+Σ⁰ reaction have not been reported before now.

Method: Themeasurements were carried out using linearly polarized photon beams incident on a liquid hydrogen target, and the …

Laser Pulsing In Linear Compton Scattering, G. A. Krafft, E. Johnson, K. Deitrick, B. Terzić, R. Kelmar, T. Hodges, J. R. Delayen

Physics Faculty Publications

Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such an …

Measurements Of Dⁿ² And Aⁿ¹: Probing The Neutron Spin Structure, D. Flay, M. Posik, D. S. Parno, K. Allada, M. Canan, C. Hyde, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d₂ of the neutron dⁿ₂ was conducted. The quantity dⁿ₂ represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the ³He spin structure functions, g₁ and g₂, after nuclear corrections had been applied to these …

Gluon Tmd In Particle Production From Low To Moderate X, I. Balitsky, A. Tarasov

Physics Faculty Publications

We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.

Measurement Of Target And Double-Spin Asymmetries For The Ep → Eπ+(N) Reaction In The Nucleon Resonance Region At Low Q², Clas Collaboration, K. P. Adhikari, S E. Kuhn, D. Adikaram, M. J. Amaryan, S. Bültmann, Gail Dodge, N. Guler, L. B. Weinstein

Physics Faculty Publications

We report measurements of target- and double-spin asymmetries for the exclusive channel ^→e^→p → eπ⁺(n) in the nucleon resonance region at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). These asymmetries were extracted from data obtained using a longitudinally polarized NH₃ target and a longitudinally polarized electron beam with energies 1.1, 1.3, 2.0, 2.3, and 3.0 GeV. The new results are consistent with previous CLAS publications but are extended to a low Q² range from 0.0065 to 0.35(GeV/c)². The Q² access was made possible by a custom-built Cherenkov detector …

Iterative Monte Carlo Analysis Of Spin-Dependent Parton Distributions, Nobuo Sato, W. Melnitchouk, S. E. Kuhn, J. J. Ethier, A. Accardi, Jefferson Lab Angular Momentum Collaboration

Physics Faculty Publications

We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳ 0.1 . The study also provides the first determination of the flavor-separated twist-3 PDFs …

A Search For The Lhcb Charmed "Pentaquark" Using Photoproduction Of J/Ψ At Threshold In Hall C At Jefferson Lab, A. Asaturyan, H. Mkrtchyan, T. Tadevosyan, S. Zhamkochyan, J. Arrington, W. Armstrong, K. Hafidi, M. Hattawy, Z. Ye, K. Aniol, H. Gao, Z. Zhao, T. Liu, X. Yan, C. Gu, C. Peng, X. Li, W. Xiong, P. Markowitz, K. Adhikari, H. Bhatt, D. Bhetuwal, J. Dunne, D. Dutta, L. El-Fassi, L. Ye, F. R. Wesselmann, X. Chen, Q. Fu, R. Wang, Y. Zhang, F. Zhao, R. Dupré, G. M. Huber, W. Li, A. Zafar, S. Bae, H. Choi, S. Choi, H. Go, J. Ha, H. Atac, B. Duran, S. Joosten, Z.-E. Meziani, M. Paolone, M. Rehfuss, N. Sparveris, J.-P. Chen, E. Chudakov, M. Diefenthaler, O. Hansen, D. Higinbotham, M. Jones, D. Meekins, L. Pentchev, E. Pooser, S. Wood

Physics Faculty Publications

We propose to measure the photo-production cross section of J/Ψ near threshold in search of the recently observed LHCb hidden charm resonances Pc(4380) and Pc(4450) consistent with "pentaquarks." The observation of these resonances in photo-production is important to differentiate the true resonance nature of the LHCb states from kinematics enhancements. The bremsstrahlung photon beam produced with an 11 GeV electron beam at CEBAF enables us to cover the energy range of J/Ψ production from the threshold photo-production energy of 8.2 GeV to an energy beyond the presumed Pc(4450) resonance production. The proposed experiment will be carried out in Hall C …

Production Of Highly Polarized Positrons Using Polarized Electrons At Mev Energier, D. Abbott, P. Adderley, A. Adeyemi, P. Aguilera, M. Ali, H. Areti, M. Baylac, J. Benesch, G. Bosson, B. Cade, A. Camsonne, L. S. Cardman, J. Clark, P. Cole, S. Covert, C. Cuevas, O. Dadoun, D. Dale, H. Dong, J. Dumas, E. Fanchini, T. Forest, E. Forman, A. Freyberger, E. Froidefond, S. Golge, J. Grames, P. Guèye, J. Hansknecht, P. Harrell, J. Hoskins, C. Hyde, B. Josey, R. Kazimi, Y. Kim, D. Machie, K. Mahoney, R. Mammei, M. Marton, J. Mccarter, M. Mccaughan, M. Mchugh, D. Mcnulty, K. E. Mesick, T. Michaelides, R. Michaels, B. Moffit, D. Moser, C. Muñoz-Camacho, J. -F. Muraz, A. Opper, M. Poelker, J. -S. Réal, L. Richardson, S. Setiniyaz, M. Stutzman, R. Suleiman, C. Tennant, C. Tsai, D. Turner, M. Ungaro, A. Variola, E. Voutier, Y. Wang, Y. Zhang

Physics Faculty Publications

The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-𝑍 target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19  MeV/c, limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

Circumstellar Dust Shells: Clues To The Evolution Of R Coronae Borealis Stars, Edward Joseph Montiel

LSU Doctoral Dissertations

The existence of extended, cold dust envelopes surrounding R Coronae Borealis (RCB) stars has been known about for over 30 years. RCB stars are an exotic group of extremely hydrogen-deficient, carbon-rich supergiants that are known for their spectacular declines in brightness (up to 8 mags) at irregular intervals. There are three possible origins of these envelopes: (1) they are fossil planetary nebulae (PNe), indicating that RCB stars formed via a final Helium-shell flash; (2) they are the remnant material from the merger of a CO and a He white dwarf binary, (3) they have been constructed from dust ejection events …

Study Of Condensed Matter Systems With Monte Carlo Simulation On Heterogeneous Computing Systems, Sheng Feng

LSU Doctoral Dissertations

We study the Edwards-Anderson model on a simple cubic lattice with a finite constant external field. We employ an indicator composed of a ratio of susceptibilities at finite momenta, which was recently proposed to avoid the difficulties of a zero momentum quantity, for capturing the spin glass phase transition. Unfortunately, this new indicator is fairly noisy, so a large pool of samples at low temperature and small external field are needed to generate results with a sufficiently small statistical error for analysis. We thus implement the Monte Carlo method using graphics processing units to drastically speed up the simulation. We …

Intracontinental Neotectonics: Case Studies From The Tian Shan Orogen And Kuqa Fold-Thrust Belt, Cindy M. Colón

LSU Doctoral Dissertations

This dissertation focuses on the kinematic properties of intracontinental deformation during short geologic time scales. Using three case studies this work characterizes active deformation at varying spatial scales within the continental interior of Eurasia. The far-field effect of the Cenozoic Indo-Asia collision is the driving force controlling deformation within the Eurasian continental interior. Active deformation across the intracontinental Tian Shan range challenges the plate tectonic model that proposes crustal deformation is concentrated along plate boundaries. This work further constrains the active kinematics of intracontinental motion that is necessary to understand the dynamics of the Eurasian intracontinental system. The two standing …

Interactions Between Local Magnetic Moments And Itinerant Charge Carriers In Fe-Based Systems, Yan Wu

LSU Doctoral Dissertations

The interactions between magnetic moments and electrons are essential in creating many of the unique properties of magnetic systems. In this thesis, I focused on two Fe-based systems employing multiple experimental techniques to investigate the coupling between localized magnetic moments and conducting charge carriers in two systems with tendencies to order into itinerant magnetic phases.\\ With systematic investigations of Fe$_{1-y}$Co$_y$Si, we discovered a field depended non-Fermi-Liquid (non-FL) behavior near its insulator-metal-transition (IMT) that appears to share the same mechanism as previously discovered in Mn doped FeSi - the underscreened Kondo effect.\\ A similar interaction of the charge carrier moments screening …

Tip-Enhanced Laser Ablation Sample Transfer For Mass Spectrometry, Chinthaka Aravinda Seneviratne

LSU Doctoral Dissertations

In this research, atomic force microscope tip-enhanced laser ablation mass spectrometry (AFM TELA-MS), an ambient sub-micrometer scale sampling method for offline MS was developed. AFM TELA was used to transfer molecules from thin films to a suspended silver wire for off-line mass spectrometry using laser desorption ionization (LDI) and matrix-assisted laser desorption ionization (MALDI). An AFM with a 30 nm radius gold-coated silicon tip was used to image the sample and to hold the tip 15 nm from the surface for material removal using a pulsed Nd:YAG laser, which provides output at wavelengths of 532 nm in the visible, 1064 …

Understanding Chemical Reactions In Novel Materials: From Metal Organic Frameworks To Oxyallyl Cations, Kiara Taylor-Edinbyrd

LSU Doctoral Dissertations

The work of this dissertation investigates the chemical processes of novel materials through quantum mechanical calculations and molecular dynamics simulations. The first section of this work focuses on probing copper based metal organic frameworks (MOFs) for their ability to catalytically release nitric oxide from s-nitrosothiol (RSNO) precursors in a slow, controlled and sustained manner and compares these findings to a free copper ion/ethanol solution. Through the use of electronic structure calculations and molecular dynamics simulations, studies are carried out to better understand how the barriers of RSNOs approach to the catalytic copper center changes with modifications to the R-group (of …

Total Synthesis Of Ht-13-A And Ht-13-B, Total Synthesis Of Aurantioclavine, Progress Towards The Synthesis Of Cycloclavine, Yilin Zhang

Graduate Theses, Dissertations, and Problem Reports (ETD)

Total synthesis of tetracyclic indole alkaloid ht-13-A and ht-13-B has been accomplished from commercially available (S)-4-amino-2-hydroxybutyric acid and trans4-hydroxy-L-proline respectively. The key synthetic steps include an acyliminium ion allylation, a Mitsunobu reaction, a palladium-catalyzed Stille-Kelly cross coupling reaction, and a carbon monoxide mediated palladium-catalyzed reductive Nheterocyclization. The total synthesis of aurantioclavine has been studied. The synthesis commenced with 2-amino-3-nitrophenol. Key synthetic steps include a Stille coupling reaction, a Heck reaction, a Lewis acid mediated cyclization and a carbon monoxide mediated palladium-catalyzed reductive N-heterocyclization. In addition, the first asymmetric total synthesis of (+)-cycloclavine has been studied. Key synthetic steps include a …