Role of mesons in the electromagnetic form factors of the nucleon

Abstract

The roles played by mesons in the electromagnetic form factors of the nucleon are explored using as a basis a model containing vector mesons with coupling to the continuum together with the asymptotic Q2 behavior of perturbative QCD. Specifically, the vector dominance model (GKex) developed by E. L. Lomon is employed, as it is known to be very successful in representing the existing high-quality data published to date. An analysis is made of the experimental uncertainties present when the differences between the GKex model and the data are expanded in orthonormal basis functions. A main motivation for the present study is to provide insight into how the various ingredients in this model yield the measured behavior, including discussions of when dipole form factors are to be expected or not, of which mesons are the major contributors, for instance, at low Q2 or large distances, and of what effects are predicted from coupling to the continuum. Such insights are first discussed in momentum space, followed by an analysis of how different and potentially useful information emerges when both the experimental and theoretical electric form factors are Fourier transformed to coordinate space. While these Fourier transforms should not be interpreted as "charge distributions," nevertheless the roles played by the various mesons, especially those which are dominant at large or small distance scales, can be explored via such experiment-theory comparisons. © 2010 The American Physical Society.

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10.1103/PhysRevC.82.045211

Publication Info

Crawford, C, T Akdogan, R Alarcon, W Bertozzi, E Booth, T Botto, JR Calarco, B Clasie, et al. (2010). Role of mesons in the electromagnetic form factors of the nucleon. Physical Review C - Nuclear Physics, 82(4). p. 45211. 10.1103/PhysRevC.82.045211 Retrieved from https://hdl.handle.net/10161/4269.

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Scholars@Duke

Gao

Haiyan Gao

Henry W. Newson Distinguished Professor of Physics

Prof. Gao's research focuses on understanding the structure of the nucleon in terms of quark and gluon degrees of freedom of Quantum Chromodynamics (QCD), search for QCD exotics, and fundamental symmetry studies at low energy to search for new physics beyond the Standard Model of electroweak interactions. Most recently, her group's studies of the structure of the nucleon have been focusing on a precision measurement of the proton (see her group's 2019 Nature paper on this topic) and deuteron charge radii to elucidate on the proton and the deuteron charge radius puzzles, and on imaging the three-dimensional structure of the nucleon in momentum space through the extraction of transverse momentum dependent parton distribution functions (TMDs), employing polarized semi-inclusive deep inelastic scattering processes. The nucleon tomography provided by TMDs will uncover the rich QCD dynamics, and provide quantitative information about the quark orbital angular momentum contribution to the proton spin. TMDs will also provide information on fundamental quantities such as the tensor charge of the nucleon, a quantity not only important for testing lattice QCD predictions, but also important for searches of new physics beyond the Standard Model together with the next generation of nucleon electric dipole moment experiments. Her group is playing leading roles in the Solenoidal Large Intensity Device (SoLID) project at Jefferson Lab, a high profile program which will make major impact on TMD physics, proton mass puzzle through precision measurement of J/psi production near threshold, and search for new physics beyond the Standard Model using parity-violating deep inelastic scattering. Most of her work utilizes the novel experimental technique of scattering polarized electrons or photons from polarized gas targets. Her group has built a number of state-of-the-art polarized gas targets including H/D internal gas target and a high-pressure polarized 3He target for photon experiments using the High Intensity Gamma Source (HIGS) facility at the Duke Free Electron Laser Laboratory (DFELL). Her research is being carried out mostly at the Thomas Jefferson National Accelerator Facility (JLab) in Newport News, Virginia, and the HIGS facility at DFELL.


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