Empirical transverse charge densities in the nucleon and in the nucleon-to-Delta transition

Prof. Carl Carlson, William and Mary
4:15 PM, Oct. 16, 2007, NC State

Using only the current empirical information on the nucleon, electromagnetic form factors we map out the transverse charge density in the proton and neutron, as viewed from a light front moving towards a transversely polarized nucleon. The talk will include a brief discussion of light-front methods of calculation and why we want to employ them, and explanation of why charge densities are better connected to form factors in a light-front viewpoint than in other viewpoints. The resulting charge densities include a dipole pattern (a result consistent with work of Einstein and Laub in 1908, in another context), in addition to the monopole field corresponding to the unpolarized density. Furthermore, we use the latest empirical information on the N to Delta transition form factors to map out the transition charge density which induces the N to Delta excitation. This transition charge density for a transversely polarized N and Delta contains monopole, dipole, and quadrupole patterns, the latter corresponding with a "deformation" of the hadron's charge distribution.