[PDF] Inclusive And Exclusive Spin Structure Measurements In The Resonance Region eBook

Author : G. E. Dodge
Publisher :
Page : pages
File Size : 50,45 MB
Release : 2003
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A program of spin structure function measurements is underway in Jefferson Lab's Hall B. We use polarized electrons incident on polarized NH3 and ND3 targets to study proton and deuteron spin observables in and above the resonance region. Results from the first set of data taken in 1998 will be presented for the first moment of g1 and for the double polarization asymmetry for exclusive pion production, which is sensitive to the spin structure of the nucleon resonances.

Author : Erhard Steffens
Publisher : Springer Science & Business Media
Page : 273 pages
File Size : 26,44 MB
Release : 2012-12-06
Category : Science
ISBN : 9401001650

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A comprehensive survey of the most recent results from the field of quark-gluon structure of the nucleon, in particular how the spin of the nucleon is shared by its constituents. After very intriguing results from CERN and SLAC at the end of the 1980s, the last decade has seen a set of second-generation experiments at high energy accelerators that have yielded precise information on the solution of the 'Spin Crisis' - as well as opening up new questions. The articles are written by experts from the leading collaboration and theory groups as well as providing an expert summary of the state of the art, the book points the way to future research directions. Its main focus is on semi-inclusive and exclusive measurements of deep inelastic lepton scattering, which enables for the first time the determination of the flavor-separated quark spin distributions. Future developments on generalized parton distributions and their interpretation as well as the transverse spin structure are also covered. An indispensable volume for all working in hadronic physics.

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Page : pages
File Size : 33,25 MB
Release : 2002
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We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer (Q2 = 0.27 -- 1.3 (GeV/c)2) and final hadronic state mass in the nucleon resonance region (W = 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target (15ND3) and detected the scattered electrons with the CEBAF Large Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal double spin asymmetry A{sub {parallel}} and the spin structure function g1{sup d}. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function g1{sup d} and study its approach to both the deep inelastic limit at large Q2 and to the Gerasimov-Drell-Hearn sum rule at the real photon limit (Q2−°. We find that the first moment varies rapidly in the Q2 range of our experiment and crosses zero at Q2 between 0.5 and 0.8 (GeV/c)2, indicating the importance of the [Delta] resonance at these momentum transfers.

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Page : pages
File Size : 26,43 MB
Release : 2003
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This paper will present a survey of recent experimental results for the g1 and g2 spin structure functions. Over the past decade, these structure functions (and the virtual photon asymmetries A1 and A2) have been well-measured in the large-Q2 scaling region using inclusive polarized deep-inelastic scattering. New precision results from Jefferson Lab are now becoming available which cover kinematic regions that were previously poorly measured or completely unmeasured. Topics covered will include: recent experiments at Jefferson Lab which have made precise measurements of g1 in the resonance region for both proton and neutron to investigate the Q2 evolution of the GDH sum rule, a new measurement of A1 for the neutron in the large-x region where valence quark dynamics dominate, new precision results for g2 from Jefferson Lab, a review of the g1 results and NLO analyses in the scaling region for the SLAC, HERMES, and SMC data. Finally, a survey of results expected from several new experime.

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Page : 214 pages
File Size : 44,96 MB
Release : 2006
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One of the biggest challenges in the study of the nucleon structure is the understanding of the transition from partonic degrees of freedom to hadronic degrees of freedom. In 1970, Bloom and Gilman noticed that structure function data taken at SLAC in the resonance region average to the scaling curve of deep inelastic scattering (DIS). Early theoretical interpretations suggested that these two very different regimes can be linked under the condition that the quark-gluon and quark-quark interactions are suppressed. Substantial efforts are ongoing to investigate this phenomenon both experimentally and theoretically. Quark-hadron duality has been confirmed for the unpolarized structure function F2 of the proton and the deuteron using data from the experimental Hall C at Jefferson Lab (JLab). Indications of duality have been seen for the proton polarized structure function g1 and the virtual photon asymmetry A1 at JLab Hall B and HERMES. Because of the different resonance behavior, it is expected that the onset of duality for the neutron will happen at lower momentum transfer than for the proton. Now that precise spin structure data in the DIS region are available at large x, data in the resonance region are greatly needed in order to test duality in spin-dependent structure functions. The goal of experiment E01-012 was to provide such data on the neutron (3He) in the moderate momentum transfer (Q2) region, 1.0 Qsup2/sup 4.0 (GeV/csup2/sup), where duality is expected to hold. The experiment ran successfully in early 2003 at Jefferson Lab in Hall B. It was an inclusive measurement of longitudinally polarized electrons scattering from a longitudinally or transversely polarized sup3/supHe target. Asymmetries and cross section differences were measured in order to extract the sup3/supHe spin structure function gsub1/sub and virtual photon asymmetry Asub1/sub in the resonance region. A test of quark-hadron duality has then been performed for the sup3/supHe and neutron structure functions. The study of spin duality for the neutron will provide a better understanding of the mechanism of the strong interaction. Moreover, if duality is well understood, our resonance data will bring information on the high x region where theoretical predictions for A

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Page : pages
File Size : 47,15 MB
Release : 2002
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Inclusive double spin asymmetries have been measured for $\vec{p}$($\vec{e}$,e') using the CLAS detector and a polarized 15NH3 target at Jefferson Lab in 1998. The virtual photon asymmetry A1, the longitudinal spin structure function, g1 (x, Q2), and the first moment [Gamma]$1\atop{p}$, have been extracted for a Q2 range of 0.15-2.0 GeV2. These results provide insight into the low Q2 evolution of spin dependent asymmetries and structure functions as well as the transition of [Gamma]$1\atop{p}$ from the photon point, where the Gerasimov, Drell and Hearn Sum Rule is expected to be satisfied, to the deep inelastic region.

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Page : pages
File Size : 41,88 MB
Release : 2000
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The spin dependent cross sections,?{sup T}12 and?{sup T}32, and asymmetries, A{sub {parallel}} and A{sub {perp}}, for 3He have been measured at the Jefferson Lab's Hall A facility. The inclusive scattering process 3{vec He}({vec e}, e)X was performed for initial beam energies ranging from 0.86 to 5.1 GeV, at a scattering angle of 15.5°. Data includes measurements from the quasielastic peak, resonance region, and the deep inelastic regime. An approximation for the extended Gcrasimov-Drell-Hcarn integral is presented at a 4-momentum transfer Q2 of 0.2-1.0 GeV2 . Also presented are results on the performance of the polarized 3He target. Polarization of 3He vvas achieved by the process of spin-exchange collisions with optically pumped rubidium vapor. The 3He polarization was monitored using the NMR technique of adiabatic fast passage (AFP). The average target polarization was approximately 35% and was determined to have a systematic uncertainty of roughly ±4% relative.

Author : Dieter Drechsel
Publisher : World Scientific
Page : 430 pages
File Size : 44,66 MB
Release : 2001-02-05
Category : Science
ISBN : 9814491381

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The history of spin in general, and of the nucleon spin structure in particular, has been full of surprises. For the past 25 years deep inelastic lepton scattering has been studied to determine the carriers of the nucleon spin. However, it was realized only recently that a full understanding of the nucleon spin will also require detailed information on the helicity structure in the resonance region, i.e. in the realm of nonperturbative QCD.This volume gives a status report on the spin structure in the nucleon resonance region, focusing on: new experimental results from SLAC and HERMES; a first glance at the JLab experiments to map out the spin structure functions at low and intermediate four-momentum transfers; the pioneering experiment at MAMI (Mainz) to determine the Gerasimov-Drell-Hearn sum rule for real photons; and recent theoretical concepts and investigations to describe the spin structure in the frameworks of higher twist expansion, phenomenological models and chiral perturbation theory.