Nuclear and Particle Physics, Astrophysics and Cosmology, T-2

At what momentum-transfer do the nucleon elastic electromagnetic form factors approach the QCD limit?

Earle Lomon
MIT

The extended Gari-Krumpelmann model of the nucleon elastic electromagnetic form factors (emff) includes the known vector meson exchanges but is modified to have the QCD momentum-transfer dependence asymptotically. It fits the data very well with reasonable form factor cut-off masses that determine the asymptotic normalization. Because of the different signs and magnitudes of the vector meson contributions to the electric and magnetic and the isotopic vector and scalar parts of the form factor, each form factor converges to the QCD value at a different momentum transfer. The slowest to converge is the neutron electric form factor, which does not approach the QCD limit until ~ 30 (GeV/c)^2 .