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Languages : en
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We review recent progress in the study of quark-hadron duality in electron-nucleon structure functions. New developments include insights into the local aspects of duality obtained using truncated moments of structure functions, which allow duality-violating higher-twist contributions to be identified in individual resonance regions. Preliminary studies of pion electropro-duction have also showed the first glimpses of duality in semi-inclusive cross sections, which if confirmed would greatly expand the scope of constraining the flavor and spin dependence of parton distributions.
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Languages : en
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Book Description
We review recent progress in the study of quark-hadron duality in electron-nucleon structure functions. New developments include insights into the local aspects of duality obtained using truncated moments of structure functions, which allow duality-violating higher-twist contributions to be identified in individual resonance regions. Preliminary studies of pion electropro-duction have also showed the first glimpses of duality in semi-inclusive cross sections, which if confirmed would greatly expand the scope of constraining the flavor and spin dependence of parton distributions.
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Languages : en
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New measurements of the spin structure functions of the proton and deuteron g1{sup p}(x, Q2) and g1{sup d}(x, Q2) in the nucleon resonance region are compared with extrapolations of target-mass-corrected next-to-leading-order (NLO) QCD fits to higher energy data. Averaged over the entire resonance region (W 2 GeV), the data and QCD fits are in good agreement in both magnitude and Q2 dependence for Q2 1.7 GeV2/c2. This ''global'' duality appears to result from cancellations among the prominent ''local'' resonance regions: in particular strong [sigma]{sub 3/2} contributions in the [Delta](1232) region appear to be compensated by strong [sigma]{sub 1/2} contributions in the resonance region centered on 1.5 GeV. These results are encouraging for the extension of NLO QCD fits to lower W and Q2 than have been used previously.
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Inclusive electron-proton and electron-deuteron inelastic cross sections have been measured at Jefferson Lab (JLab) in the resonance region, at large Bjorken x, up to 0.92, and four-momentum transfer squared Q2 up to 7.5 GeV2 in the experiment E00-116. These measurements are used to extend to larger x and Q2 precision, quantitative, studies of the phenomenon of quark-hadron duality. Our analysis confirms, both globally and locally, the apparent violation of quark-hadron duality previously observed at a Q2 of 3.5 GeV2 when resonance data are compared to structure function data created from CTEQ6M and MRST2004 parton distribution functions (PDFs). More importantly, our new data show that this discrepancy saturates by Q2 ~ 4 Gev2, becoming Q2 independent. This suggests only small violations of Q2 evolution by contributions from the higher-twist terms in the resonance region which is confirmed by our comparisons to ALEKHIN and ALLM97. We conclude that the unconstrained strength of the CTEQ6M and MRST2004 PDFs at large x is the major source of the disagreement between data and these parameterizations in the kinematic regime we study and that, in view of quark-hadron duality, properly averaged resonance region data could be used in global QCD fits to reduce PDF uncertainties at large x.
Author: Simonetta Liuti
Publisher: World Scientific
ISBN: 9814478490
Category : Science
Languages : en
Pages : 298
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Book Description
While perturbative QCD methods fully describe experimental results at high energies, and chiral perturbation theory is the low energy effective theory of the strong interactions, a form of duality is observed connecting these two regimes. In these intermediate kinematics, a wide variety of reactions are observed which can be described simultaneously by single particle (quark) scattering, and by exclusive resonance (hadron) scattering.The contributions in this proceedings volume discuss recent and existing results, and aim to foster current and future research, investigating the phenomenon of quark-hadron duality.This unique volume contains research work by scientists from different arenas of hadronic physics, dealing with different manifestations of quark-hadron duality.
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Languages : en
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The authors examine the consequences of local duality for elastic scattering, and derive model-independent relations between structure functions at x(approximately)1 and elastic electromagnetic form factors.
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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
Author: Tony Forest
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Languages : en
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Inclusive electron-nucleon scattering data from Jefferson Lab's Hall B has been analyzed to test quark-hadron duality for the polarized structure function g1(x, Q{sup 2}) over a Q{sup 2} range from 0.2 to 3.5 GeV{sup 2}/c{sup 2}. Incident polarized electron beam energies of 1.6 and 5.7 GeV were scattered by polarized {sup 15}NH{sub 3} and {sup 15}ND{sub 3} targets. The measurements of g1(x, Q{sup 2}) in the resonance region appear to be equivalent to a fit of g1(x, Q{sup 2}) in the deep inelastic scattering region at high Q{sup 2}. A quantitative test comparing the ratio of first moment in the resonance region to the first moment in the deep inelastic region is consistent with unity when Q{sup 2}> 2.0 GeV{sup 2}/c{sup 2} but substantially departs from unity when Q{sup 2}
Author: Alessandra Fantoni
Publisher: World Scientific
ISBN: 9812774130
Category : Science
Languages : en
Pages : 298
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Book Description
While perturbative QCD methods fully describe experimental results at high energies, and chiral perturbation theory is the low energy effective theory of the strong interactions, a form of duality is observed connecting these two regimes. In these intermediate kinematics, a wide variety of reactions are observed which can be described simultaneously by single particle (quark) scattering, and by exclusive resonance (hadron) scattering. The contributions in this proceedings volume discuss recent and existing results, and aim to foster current and future research, investigating the phenomenon of quark-hadron duality. This unique volume contains research work by scientists from different arenas of hadronic physics, dealing with different manifestations of quark-hadron duality. Sample Chapter(s). Chapter 1: Introductory Remarks on Duality in Lepton-Hadron Scattering (490 KB). Contents: Introduction and Review: Experimental and Theoretical Status: Duality in the Polarized Structure Functions (H P Blok); Spin Structure of the Nucleon and Aspects of Duality (Z E Meziani); Duality and Confinement: Quark Models of Duality in Electron and Neutrino Scattering (W Melnitchouk); Hadron Structure on the Back of an Envelope (A W Thomas et al.); Spin-Flavor Decomposition and in Polarized Semi-Inclusive Deep Inelastic Scattering Experiments at Jefferson Lab (X Jiang); Duality in Photoproduction: Duality in Vector-Meson Production (A Donnachie); Onset of Scaling in Exclusive Processes (M Mirazita); Duality in Nuclei: A Partonic Picture of Jet Fragmentation in Nuclei (X-N Wang); Quark Gluon Plasma and Hadronic Gas on the Lattice (M P Lombardo); Duality in Neutrino Experiments: Neutrinos and Local Duality (F Steffens & K Tsushima); Duality and QCD: Higher Twist Effects in Polarized DIS (E Leader et al.); Highly Excited Hadrons in QCD and Beyond (M Shifman); Future Perspectives: Transverse Polarization and Quark-Hadron Duality (O V Teryaev); Research Perspectives with the Jefferson Lab (K de Jager); Perspectives with PANDA (P Gianotti); Summary Talk (P Hoyer); and other papers. Readership: Researchers, academics and lecturers in high energy, particle and nuclear physics.
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The Thomas Jefferson National Accelerator Facility (JLab) experiment BONuS used a novel spectator-tagging technique to measure the inclusive electron-free neutron scattering cross section and extract the F2 structure function. This data was used to reconstruct moments of F2 in the three prominent resonance region and the moments integrated over the entire resonance region. Comparisons of the experimental results with moments obtained from global parton distribution function parametrization seem to suggest that the quark-hadron duality hypothesis holds locally for the neutron in the second and third resonance regions down to Q2 of 1 GeV2; with up to 20% violations observed in the first resonance region.
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Using a recently developed technique we extract the neutron F_2^n structure function from new inclusive proton and deuteron data in the large-x region, and test the validity of quark-hadron duality in the neutron. We establish for the first time the accuracy of duality in the low-lying neutron resonance regions over a range of Q^2, and compare with the corresponding results on the proton. Our findings open the possibility of using averaged resonance region data to constrain parton distributions at large x.
