Form factors in lattice QCD |
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Authors: | B B Brandt S Capitani M Della Morte D Djukanovic J Gegelia G von Hippel A Jüttner B Knippschild H B Meyer H Wittig |
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Institution: | 1.Institut für Kernphysik,University of Mainz,Mainz,Germany;2.Helmholtz Institute Mainz,University of Mainz,Mainz,Germany;3.CERN, Physics Department,Geneva 23,Switzerland |
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Abstract: | Lattice simulations of QCD have produced precise estimates for the masses of the lowest-lying hadrons which show excellent
agreement with experiment. By contrast, lattice results for the vector and axial vector form factors of the nucleon show significant
deviations from their experimental determination. We present results from our ongoing project to compute a variety of form
factors with control over all systematic uncertainties. In the case of the pion electromagnetic form factor we employ partially
twisted boundary conditions to extract the pion charge radius directly from the linear slope of the form factor near vanishing
momentum transfer. In the nucleon sector we focus specifically on the possible contamination from contributions of higher
excited states. We argue that summed correlation functions offer the possibility of eliminating this source of systematic
error. As an illustration of the method we discuss our results for the axial charge, g
A
, of the nucleon. |
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