Download or read book A Measurement of Unpolarized Cross Sections and Polarized Cross Section Differences of Deeply Virtual Compton Scattering on the Proton at Jefferson Laboratory Using CLAS e1 dvcs2 written by Nicholas A. N. Hirlinger Saylor and published by . This book was released on 2013 with total page 624 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A measurement of unpolarized cross sections and polarized cross section differences of deeply virtual compton scattering on the proton at Jefferson Laboratory using Clas written by Nicholas Hirlinger-Saylor and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cette thèse a pour sujet l'étude de la réaction de la Diffusion Compton Profondément Virtuelle (DVCS) sur le proton e + p -> e' + p' + gamma (DVCS). Cette réaction est mesurée en analysant l'expérience e1-dvcs2 qui a eu lieu dans le Hall B du Jefferson Laboratory avec CLAS. La prise de données s'est déroulée du 22 octobre 2008 jusqu'au 23 janvier 2009. Cette analyse a pour but la détermination des sections efficaces non polarisées et les différences de sections efficaces polarisées du DVCS, dans divers bins en xB, Q^2, t et phi. Cette analyse compare les sections efficaces avec plusieurs mesures existantes du DVCS: une analyse parallèle de e1-dvcs2 et une analyse de e1-dvcs1. En factorisant l'élément de matrice qui correspond au DVCS en deux parties, calculables en QCD perturbative et non perturbative, on peut accéder aux Distributions de Partons Généralisées (GPDs) du proton, et ainsi obtenir une vue en 3D des distributions spatiales et en impulsion des quarks et des gluons dans le proton.
Download or read book Discussion on the Recent Proton DVCS Results of Jefferson Lab written by and published by . This book was released on 2008 with total page 45204 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the recent data issued from the Halls A and B of Jefferson Laboratory for the Deep Virtual Compton Scattering Process on the proton. An important set of data for beam spin asymmetries, unpolarized cross sections and differences of polarized cross sections have been obtained. We modestly attempt a first "global" analysis of these three observables at a single $x_B$, $Q^2$ and $-t$ kinematic point. We find that it is extremely challenging to describe simultaneously these data in the framework of a few Generalized Parton Distributions models.
Download or read book Deeply Virtual Compton Scattering Cross Section Measured with CLAS written by and published by . This book was released on 2014 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Generalized Parton Distributions (GPDs) provide a new description of nucleon structure in terms of its elementary constituents, the quarks and the gluons. Including and extending the information provided by the form factors and the parton distribution functions, they describe the correlation between the transverse position and the longitudinal momentum fraction of the partons in the nucleon. Deeply Virtual Compton Scattering (DVCS), the electroproduction of a real photon on a single quark in the nucleon eN --> e'N'g, is the exclusive process most directly interpretable in terms of GPDs. A dedicated experiment to study DVCS with the CLAS detector at Jefferson Lab has been carried out using a 5.9-GeV polarized electron beam and an unpolarized hydrogen target, allowing us to collect DVCS events in the widest kinematic range ever explored in the valence region : 1.0
Download or read book Deeply Virtual Compton Scattering at JLab Hall A written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e, e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.
Download or read book Deeply Virtual Compton Scattering on Longitudinally Polarized Protons and Neutrons at CLAS written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper focuses on a measurement of deeply virtual Compton scattering (DVCS) performed at Jefferson Lab using a nearly-6-GeV polarized electron beam, two longitudinally polarized (via DNP) solid targets of protons (NH3) and deuterons (ND3) and the CEBAF Large Acceptance Spectrometer. Here, preliminary results for target-spin asymmetries and double (beam-target) asymmetries for proton DVCS, as well as a very preliminary extraction of beam-spin asymmetry for neutron DVCS, are presented and linked to Generalized Parton Distributions.
Download or read book E00 110 Experiment at Jefferson Lab Hall A written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present final results on the photon electroproduction ($\vec{e}p\rightarrow ep\gamma$) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed resulting in photon electroproduction cross sections at new kinematic settings, for a total of 588 experimental bins. Results of the $Q^2$- and $x_B$-dependences of both the helicity-dependent and helicity-independent cross sections are discussed. The $Q^2$-dependence illustrates the dominance of the twist-2 handbag amplitude in the kinematics of the experiment, as previously noted. Thanks to the excellent accuracy of this high luminosity experiment, it becomes clear that the unpolarized cross section shows a significant deviation from the Bethe-Heitler process in our kinematics, compatible with a large contribution from the leading twist-2 DVCS$^2$ term to the photon electroproduction cross section. The necessity to include higher-twist corrections in order to fully reproduce the shape of the data is also discussed. The DVCS cross sections in this study represent the final set of experimental results from E00-110, superseding the previous publication.
Download or read book Virtual Deep Compton Scattering from Hall A at Jefferson Laboratory Diffusion Compton Profondement Virtuelle Dans Le Hall A Au Jefferson Laboratory written by and published by . This book was released on 2005 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generalized Parton Distributions (GPDs), introduced in the late 90s, provide a universal description of hadrons in terms of the underlying degrees of freedom of Quantum Chromodynamics: quarks and gluons. GPDs appear in a wide variety of hard exclusive reactions and the advent of high luminosity accelerator facilities has made the study of GPDs accessible to experiment. Deeply Virtual Compton Scattering (DVCS) is the golden process involving GPDs. The first dedicated DVCS experiment ran in the Hall A of Jefferson Lab in Fall 2004. An electromagnetic calorimeter and a plastic scintillator detector were constructed for this experiment, together with specific electronics and acquisition system. The experiment preparation, data taking and analysis are described in this document. Results on the absolute cross section difference for opposite beam helicities provide the first measurement of a linear combination of GPDs as a function of the momentum transfer to the nucleon.
Download or read book Deeply Virtual Compton Scattering with CLAS12 written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview is given about the capabilities provided by the JLab 12 GeV Upgrade to measure deeply virtual exclusive processes with high statistics and covering a large kinematics range in the parameters that are needed to allow reconstruction of a spatial image of the nucleon's quark structure. The measurements planned with CLAS12 will cross section asymmetries with polarized beams and with longitudinally and transversely polarized proton targets in the constrained kinematics $x = \pm \xi$. In addition, unpolarized DVCS cross sections, and doubly polarized beam target asymmetries will be measured as well. In this talk only the beam and target asymmetries will be discussed.
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 Measurement of Differential Cross Sections and Cx and Cz for Gamma Photon proton Going to Kaon lambda Baryon and Gamma Photon proton Going to Kaon sigma Baryon Using CLAS at Jefferson Lab written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work presents several observables for the reactions [gamma] p → K+[Lambda] and [gamma] p → K+[Sigma]°. In addition to measuring differential cross sections, we have made first measurements of the double polarization observables Cx and Cz. Cx and C z characterize the transfer of polarization from the incident photon to the produced hyperons. Data were obtained at Jefferson Lab using a circularly polarized photon beam at endpoint energies of 2.4, 2.9, and 3.1 GeV. Events were detected with the CLAS spectrometer. In the [Lambda] channel, the cross sections support the recent observation of new resonant structure at W = 1900 MeV. Studies of the invariant cross section, dsdd show scaling behavior suggesting that the production mechanism becomes t-channel dominated near threshold at forward kaon angles. The double polarization observables show that the recoiling [Lambda] is almost maximally polarized along the direction of the incident photon from mid to forward kaon angles. While [Sigma]o differential cross sections are of the same magnitude as the [Lambda] differential cross sections, there is evidence of different physics dominating the production mechanism. The [Sigma]° invariant cross sections do not show the same t-scaling behavior present in the [Lambda] results. The double polarization observables indicate that the [Sigma]° is not polarized as strongly as the [Lambda]. They also fail to identify one preferred polarization axis. Complete interpretation of these results will rely on model calculations. Currently available isobar models obtain varying degrees of success while attempting to predict the double polarization observables. While the models are in better agreement with the differential cross sections, discrepancies with our cross sections indicate that they must be re-optimized in light of the new data. While the data suggest that a Regge model would provide a good description of K+[Lambda] over most of the range in W, the available Regge calculation overstates the strength of the cross section and does not predict Cx and Cz correctly.
Download or read book Polarization Observables in Virtual Compton Scattering written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Virtual Compton Scattering (VCS) is an important reaction for understanding nucleon structure at low energies. By studying this process, the generalized polarizabilities of the nucleon can be measured. These observables are a generalization of the already known polarizabilities and will permit theoretical models to be challenged on a new level. More specifically, there exist six generalized polarizabilities and in order to disentangle them all, a double polarization experiment must be performed. Within this work, the VCS reaction p(e, e p)gamma was measured at MAMI using the A1 Collaboration three spectrometer setup with Q2=0.33 (GeV/c)2. Using the highly polarized MAMI beam and a recoil proton polarimeter, it was possible to measure both the VCS cross section and the double polarization observables. Already in 2000, the unpolarized VCS cross section was measured at MAMI. In this new experiment, we could confirm the old data and furthermore the double polarization observables were measured for the first time. The data were taken in five periods between 2005 and 2006. In this work, the data were analyzed to extract the cross section and the proton polarization. For the analysis, a maximum likelihood algorithm was developed together with the full simulation of all the analysis steps. The experiment is limited by the low statistics due mainly to the focal plane proton polarimeter efficiency. To overcome this problem, a new determination and parameterization of the carbon analyzing power was performed. The main result of the experiment is the extraction of a new combination of the generalized polarizabilities using the double polarization observables.
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 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 Virtual Compton Scattering and Neutral Pion Electro production from the Proton in the Nucleon Resonance Region written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The experiment (E93-050) at Jefferson Lab measured the ep [yields] ep[gamma] and ep [yields] ep[pi][sup 0] cross sections in the nucleon resonance region, from the threshold to W = 1.9 GeV at Q[sup 2] = 1 GeV[sup 2] for backward emission of the [gamma] or [pi][sup 0].
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 Polarization and Differential Cross Sections in Proton proton and Proton nucleus Scatterings at 730 MeV written by Paul G. McManigal and published by . This book was released on 1963 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:
