Download or read book Measurements of Polarization Transfers in Real Compton Scattering by a Proton Target at JLAB written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis work, results of the analysis of the polarization transfers measured in real Compton scattering (RCS) by the Collaboration E07-002 at the Je fferson Lab Hall-C are presented. The data were collected at large scattering angle (theta_cm = 70deg) and with a polarized incident photon beam at an average energy of 3.8 GeV. Such a kind of experiments allows one to understand more deeply the reaction mechanism, that involves a real photon, by extracting both Compton form factors and Generalized Parton Distributions (GPDs) (also relevant for possibly shedding light on the total angular momentum of the nucleon). The obtained results for the longitudinal and transverse polarization transfers K_LL and K_LT, are of crucial importance, since they confirm unambiguously the disagreement between experimental data and pQCD prediction, as it was found in E99-114 experiment, and favor the Handbag mechanism. The E99-114 and E07-002 results can contribute to attract new interest on the great yield of the Compton scattering by a nucleon target, as demonstrated by the recent approval of an experimental proposal submitted to the Jefferson Lab PAC 42 for a Wide-angle Compton Scattering experiment, at 8 and 10 GeV Photon Energies. The new experiments approved to run with the updated 12 GeV electron beam at JLab, are characterized by much higher luminosities, and a new GEM tracker is under development to tackle the challenging backgrounds. Within this context, we present a new multistep tracking algorithm, based on (i) a Neural Network (NN) designed for a fast and efficient association of the hits measured by the GEM detector which allows the track identification, and (ii) the application of both a Kalman filter and Rauch-Tung-Striebel smoother to further improve the track reconstruction. The full procedure, i.e. NN and filtering, appears very promising, with high performances in terms of both association effciency and reconstruction accuracy, and these preliminary results will be discussed in detail in the last chapters.
Download or read book Measurement of Deeply Virtual Compton Scattering with a Polarized Proton Target written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The longitudinal target-spin asymmetry A{sub UL} for the exclusive electroproduction of high energy photons was measured for the first time in p(e, e'p/gamma). The data have been accumulated at Jefferson Lab with the CLAS spectrometer using 5.7 GeV electrons and a longitudinally polarized NH3 target. A significant azimuthal angular dependence was observed, resulting from the interference of the Deeply Virtual Compton Scattering and Bethe-Heitler processes. The amplitude of the sin[phi] moment is 0.252 +/- 0.042(stat) +/- 0.020(sys). Theoretical calculations are in good agreement with the magnitude and the kinematic dependence of the target-spin asymmetry, which is sensitive to the generalized parton distributions H and H-tilde.
Download or read book Polarisation Transfer in Proton Compton Scattering at High Momentum Transfer written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Jefferson Lab Hall A experiment E99-114 comprised a series of measurements to explore proton Compton scattering at high momentum transfer. For the first time, the polarisation transfer observables in the p (~ 0 ~ p) reaction were measured in the GeV energy range, where it is believed that quark-gluon degrees of freedom begin to dominate. The experiment utilised a circularly polarised photon beam incident on a liquid hydrogen target, with the scattered photon and recoil proton detected in a lead-glass calorimeter and a magnetic spectrometer, respectively.
Download or read book Measurements of Compton Scattering on the Proton at 2 6 GeV written by and published by . This book was released on 2006 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Similar to elastic electron scattering, Compton Scattering on the proton at high momentum transfers(and high p⊥) can be an effective method to study its short-distance structure. An experiment has been carried out to measure the cross sections for Real Compton Scattering (RCS) on the proton for 2.3-5.7 GeV electron beam energies and a wide distribution of large scattering angles. The 25 kinematic settings sampled a domain of s = 5-11(GeV/c)2,-t = -7(GeV/c)2 and -u = 0.5-6.5(GeV/c)2. In addition, a measurement of longitudinal and transverse polarization transfer asymmetries was made at a 3.48 GeV beam energy and a scattering angle of ?cm = 120°. These measurements were performed to test the existing theoretical mechanisms for this process as well as to determine RCS form factors. At the heart of the scientific motivation is the desire to understand the manner in which a nucleon interacts with external excitations at the above listed energies, by comparing and contrasting the two existing models – Leading Twist Mechanism and Soft Overlap ?Handbag? Mechanism – and identify the dominant mechanism. Furthermore, the Handbag Mechanism allows one to calculate reaction observables in the framework of Generalized Parton Distributions (GPD), which have the function of bridging the wide gap between the exclusive(form factors) and inclusive(parton distribution functions) description of the proton. The experiment was conducted in Hall A of Thomas Jefferson National Accelerator Facility(Jefferson Lab). It used a polarized and unpolarized electron beam, a 6% copper radiator with the thickness of 6.1% radiation lengths (to produce a bremsstrahlung photon beam), the Hall A liquid hydrogen target, a high resolution spectrometer with a focal plane polarimeter, and a photon hodoscope calorimeter. Results of the differential cross sections are presented, and discussed in the general context of the scientific motivation.
Download or read book Measurements of Compton Scattering on the Proton at 2 6 GeV written by Areg Danagoulian and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Real Photon Scattering on the Proton written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The physics of real photon exclusive scattering on the proton and JLab experiment E99-114 is discussed. Data on Compton form factors at s up to 11 (GeV/c)2 and t up to 6.5 (GeV/c)2 have been obtained. The polarization transfer parameter K{sub LL} is found to be in fair agreement with the handbag diagram predictions. Possible additional polarization transfer measurements are outlined.
Download or read book First Measurement of Deeply Virtual Compton Scattering with Polarized Proton Target written by Shifeng Chen and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polarization Transfer in Wide angle Compton Scattering and Single pion Photoproduction from the Proton written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The WACS polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of [theta]Pcm = 70°. The longitudinal transfer KLL, measured to be 0.645 ± 0.059 ± 0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ~3 times larger than predicted by the GPD-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Download or read book Exclusive Processes at High Momentum Transfer written by A. V. Radyushkin and published by World Scientific. This book was released on 2002 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the physics of exclusive processes at high momentum transfer and their description in terms of generalized parton distributions, perturbative QCD, and relativistic quark models. It covers recent developments in the field, both theoretical and experimental. Contents: Perspectives on Exclusive Processes in QCD (S J Brodsky); High-t Meson Photo- and Electroproduction: A Window on Partonic Structure of Hadrons (J-M Laget); Nucleon Hologram with Exclusive Leptoproduction (A Belitsky & D Muller); QCD Factorization for the Pion Diffractive Dissociation into Two Jets (D Yu Ivanov); GPDs, Form Factors and Compton Scattering (P Kroll); Real Compton Scattering from the Proton (A Nathan); Resonance Exchange Contributions to Wide-Angle Compton Scattering: The D-Term (T Oppermann); Proton-Antiproton Annihilation into Two Photons at Large s (C Weiss); Quark--Hadron Duality Studies at Jefferson Lab; An Overview of New and Exisiting Results (C Keppel); Novel Hard Semiexclusive Processes and Color Singlet Clusters in Hadrons (M Strikman et al.); and other papers. Readership: Theoretical and experimental researchers in nuclear and elementary particle physics.
Download or read book Exclusive Compton Scattering on the Proton written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An experiment is proposed to measure the cross sections for Real Compton Scattering from the proton in the energy range 3-6 GeV and over a wide angular range; and to measure the longitudinal and transverse components of the polarization transfer to the recoil proton at a single kinematic point. Together; these measurements will test models of the reaction mechanism and determine new structure functions of the proton that are related to the same nonforward parton densities that determine the elastic electron scattering form factors and the parton densities. The experiment utilizes an untagged bremsstrahlung photon beam and the standard Hall A cryogenic targets. The scattered photon is detected in a photon spectrometer; currently under construction. The coincident recoil proton is detected in one of the Hall A magnetic spectrometers and its polarization components are measured in the existing Focal Plane Polarimeter. This proposal extends and supercedes E97-108 which was approved by PAC13.
Download or read book Deeply Virtual Compton Scattering at Jefferson Lab written by Frédéric Georges and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introduced in the mid 90's, Generalized Parton Distributions (GPDs) are now a key element in the study of the nucleon internal structure. GPDs are a generalization of Form Factors and Parton Distribution Functions. They encapsulate both spatial and momentum distributions of partons inside a nucleon, allowing to perform its three-dimensional tomography. Furthermore, they allow to derive the total orbital angular momentum of quarks through the Ji sum rule, which is a crucial point to unravel the nucleon spin structure. By providing a more complete description of hadrons in terms of quarks and gluons, a deeper understanding of Quantum Chromodynamics can be reached.GPDs are experimentally accessible through deeply exclusive electro-production processes, and one of the simplest channels available is Deeply Virtual Compton Scattering (DVCS). A worldwide experimental program was started in the early 2000's to extract these GPDs. The DVCS experiment E12-06-114 performed at Jefferson Laboratory Hall A (Virginia, USA) between 2014 and 2016, is encompassed in this program. The aim of this experiment is to extract with high precision the DVCS helicity-dependent cross sections as a function of the momentum transfer Q2, for fixed values of the Bjorken variable xBj, on a proton target. The recent upgrade of the accelerator facility to 12 GeV allows to cover a larger Q2 range than in previous measurements and probe yet unexplored kinematic regions, while the polarized electron beam allows the separation of the contributions from the real and imaginary parts of the DVCS amplitude to the total cross section. In this document, a brief summary of the worldwide experimental program for the study of GPDs will be provided, followed by a description of the E12-06-114 apparatus and data analysis. Finally, the results of the unpolarized and polarized cross-section measurements are presented and compared to a few selected models.
Download or read book Target spin Asymmetry Measurements for Deeply Virtual Compton Scattering on Longitudinally Polarized Protons written by Erin E. Seder and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polarization in Proton Proton Scattering Using a Polarized TARGET Part I 0 330 to 0 740 GeV Part II 1 70 to 6 15 GeV written by and published by . This book was released on 1964 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using the Berkeley polarized-proton target, we have measured the polarization parameter P([theta]) for proton-proton (p-p) scattering. The measurements were obtained at beam kinetic energies of 0.330, 0.680, and 0.740 GeV at the 184-in. synchrocyclotron and 1.70, 2.85, 3.50, 4.00, 5.05, and 6.15 GeV at the Bevatron. The angular regions measured were from 20 to 100 degrees center of mass; the square of the four-momentum transfer ranged from 0.1 to 0.8 (GeV/c)2.
Download or read book Exclusive Reactions at High Momentum Transfer written by A. V. Radyushkin and published by World Scientific. This book was released on 2008 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exclusive reactions are becoming one of the major sources of information about the deep structure of nucleons and other hadrons. The 2007 International Workshop held at Jefferson Lab in Newport News, Virginia, USA - the world's leading facility performing research on nuclear, hadronic and quark-gluon structure of matter - focused on the application of a variety of exclusive reactions at high momentum transfer, utilizing unpolarized and polarized beams and targets, to obtain information about nucleon ground-state and excited-state structure at short distances. This is a subject which is central to the programs of current accelerators and especially planned future facilities. This proceedings volume contains, in concentrated form, information about the newest developments, both theoretical and experimental, in the study of hard exclusive reactions.
Download or read book Exclusive Reactions At High Momentum Transfer Proceedings Of The International Workshop written by Anatoly Radyushkin and published by World Scientific. This book was released on 2008-03-13 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exclusive reactions are becoming one of the major sources of information about the deep structure of nucleons and other hadrons. The 2007 International Workshop held at Jefferson Lab in Newport News, Virginia, USA — the world's leading facility performing research on nuclear, hadronic and quark-gluon structure of matter — focused on the application of a variety of exclusive reactions at high momentum transfer, utilizing unpolarized and polarized beams and targets, to obtain information about nucleon ground-state and excited-state structure at short distances. This is a subject which is central to the programs of current accelerators and especially planned future facilities.This proceedings volume contains, in concentrated form, information about the newest developments, both theoretical and experimental, in the study of hard exclusive reactions.
Download or read book Polarization Transfer in Proton Compton Scattering at High Momentum Transfer written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Compton scattering from the proton was investigated at s = 6.9 GeV2 and t = -4.0 TeV2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton and in disagreement with a prediction of pQCD based on a two-gluon exchange mechanism.
Download or read book Compton Scattering Polarimetry for the Determination of the Proton s Weak Charge Through Measurements of the Parity Violating Asymmetry of 1H e E p written by and published by . This book was released on 2016 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Standard Model has been a theory with the greatest success in describing the fundamental interactions of particles. As of the writing of this dissertation, the Standard Model has not been shown to make a false prediction. However, the limitations of the Standard Model have long been suspected by its lack of a description of gravity, nor dark matter. Its largest challenge to date, has been the observation of neutrino oscillations, and the implication that they may not be massless, as required by the Standard Model. The growing consensus is that the Standard Model is simply a lower energy effective field theory, and that new physics lies at much higher energies. The Qweak Experiment is testing the Electroweak theory of the Standard Model by making a precise determination of the weak charge of the proton (Qpw). Any signs of "new physics" will appear as a deviation to the Standard Model prediction. The weak charge is determined via a precise measurement of the parity-violating asymmetry of the electron-proton interaction via elastic scattering of a longitudinally polarized electron beam of an un-polarized proton target. The experiment required that the electron beam polarization be measured to an absolute uncertainty of 1%. At this level the electron beam polarization was projected to contribute the single largest experimental uncertainty to the parity-violating asymmetry measurement. This dissertation will detail the use of Compton scattering to determine the electron beam polarization via the detection of the scattered photon. I will conclude the remainder of the dissertation with an independent analysis of the blinded Qweak.
