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Jones, M.; Aniol, K.; Baker, F. T.; Berthot, J.; Bertin, P.Y.; Bertozzi, W.; Besson, A.; Bimbot, L.; Boeglin, W.; Brash, E. J.

doi:10.1103/physrevlett.84.1398

Cited by 729 publications

(549 citation statements)

References 30 publications

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“…[79] for definitions.). In the model of Frank, Jennings and Miller [81,82], the strong decrease of G p E /G p M with Q 2 emerges as an important consequence of the spin-dependent relativistic effects on the light-front quark wavefunctions embodied by the Melosh rotation (2.13) which is qualitatively confirmed by the recoil polarization data [32,31,33]. This model tends to predict a somewhat faster Despite the relative phenomenological success of nucleon models based entirely on constituent quarks, the shortcomings of these models are well known.…”

Section: Constituent Quark Modelssupporting

confidence: 68%

“…In 1973, a VMD-based model by Iachello et al [66] was among the earliest to predict a decrease of the proton G E /G M ratio for Q 2 ≥ 1 GeV 2 , which was in rough agreement with the not-yet-available recoil polarization data from Jefferson Lab [32,33,31]. In this model, as few as three adjustable parameters were used to fit the form factor data available at the time.…”

Section: Dispersion Relations and Vector Meson Dominancesupporting

confidence: 51%

“…The recoil polarization data [32,33,31] for F 2 , it will be interesting to determine the extent to which this scaling continues to be satisfied. The ratio of Pauli and Dirac form factors F 2 /F 1 is given in terms of Sachs form factors by …”

Section: Form Factors and Perturbative Qcdmentioning

confidence: 99%

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Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Puckett

2010

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The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q 2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH 2 analyzers. The scattered electron was detected in a largeacceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors G AcknowledgmentsThis thesis would not have been possible without the support and efforts of many, many people. It would be impossible to give all due credit to all of the individual efforts that went into designing, planning, staging, and executing this experiment, and the subsequent analysis of the data. Therefore, any omissions from the following acknowledgments are in no way meant to diminish those contributions.I would like to thank the members of the GEp-III collaboration whose tireless efforts made experiments E04-108 and E04-019 a success. This includes the spokespeople; Ed Brash, Mark Jones, Charles Perdrisat and Vina Punjabi, and the other outstanding physicists involved in the core collaboration. I thank Frank Wesselmann for his successful leadership of the testing, installation, commissioning and operation of the Focal Plane Polarimeter, and his significant contribution to the data analysis in the form of the event decoding and tracking software for the FPP drift chambers. I thank Mark Jones for his encyclopedic knowledge of experimental Hall C and for his outsized contribution to making the various parts of the experiment work together as a whole, and for being called upon more often than not to troubleshoot problems with the experiment as they occurred. Mark's many important contributions to the data analysis included the optimization of the HMS reconstruction coefficients. Much of what I have learned about the actual hands-on require...

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Section: Constituent Quark Modelssupporting

confidence: 68%

Section: Dispersion Relations and Vector Meson Dominancesupporting

confidence: 51%

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Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Puckett

2010

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“…Traditionally they have been extracted under the assumption of one-photon exchange via the Rosenbluth cross section in (4.40). It came as quite a surprise when the polarisation transfer measurements at Jefferson Lab revealed a ratio G p E /G p M that falls off and points towards a zero crossing at larger Q 2 [568][569][570][571], in stark contrast to the Rosenbluth measurements which had predicted a constant ratio. The question of the zero crossing for G p E is not yet settled because the experimental errors are still too large, but the situation is expected to change in the near future with the Jefferson Lab 12 GeV program where measurements in Halls A, B and C will extend the data range for G p E , G n E , and G n M up to the 10 -14 GeV 2 region [572].…”

Section: Nucleon Electromagnetic Form Factorsmentioning

confidence: 84%

“…In this respect, new experiments with polarised beams and/or polarised targets performed at Jefferson Lab allowed to extract the ratio G E /G M directly. However, the resulting ratio disagrees with the scaling predictions and shows a falloff with t, even pointing towards a zero crossing at larger t [568][569][570][571].…”

Section: Overview Of Two-photon Physicsmentioning

confidence: 85%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

436

530

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We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon processes and Compton scattering determined in the DysonSchwinger framework with those of lattice QCD and the available experimental data. The general aim is to identify the underlying physical mechanisms behind the plethora of observable phenomena in terms of the underlying quark and gluon degrees of freedom.

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Generalized parton distributions, nucleon form factors, and large-t processes

Vanderhaeghen

2004

Ann. Phys.

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The connection of generalized parton distributions (GPDs) to processes at large momentum transfer (high-t), and the links between GPDs and elastic nucleon form factors are discussed here. These links, in the form of sum rules, represent powerful constraints on parametrizations of GPDs. A Regge parametrization for the GPDs at small-t, which is surprisingly observed from the chiral quark soliton model results, is extended to the large-t region and it is found to catch the basic features of proton and neutron electromagnetic form factor data. It is furthermore discussed how these GPDs at large-t enter into two-photon exchange processes and resolve the discrepancy between Rosenbluth and polarization experiments of elastic electron nucleon scattering.

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GEp/GMp

Cited by 729 publications

References 30 publications

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Baryons as relativistic three-quark bound states

Generalized parton distributions, nucleon form factors, and large-t processes

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