Meson Electroproduction Experiments At Jefferson Lab And The Kaon Form Factor
2017 May 04
2017 May 09
Pion and kaon form factors are of particular interest in our understanding of hadron structure as they are connected to the Goldstone modes of dynamical chiral symmetry breaking. The last decade saw a dramatic improvement in precision of charged pion form factor data and new results have become available on the pion transition form factor. Plans exist to nearly quadruple the momentum transfer over which the charged pion form factor is known. Data on the kaon form factor are sparse, mainly limited to the region that constrains the kaon electromagnetic radius from kaon-atomic electron scattering data. Kaon electro-production cross section data at large virtual photon mass allow one, in principle, to constrain the kaon form factor, although technical difficulties grow as compared to the pion case due to the larger kaon mass and further distance from the pole. Most of the precision cross section measurements at the 6 GeV Jefferson Lab were primarily designed for pions, but some of these experiments also captured kaons in their acceptance. Preliminary kaon cross section results from such experiments show an indication of kaon pole dominance allowing for the first extractions of the kaon form factor from kaon electroproduction data. Planned 12 GeV experiments will further investigate the role of the kaon pole and are anticipated to extend form factor extractions to $Q^2 \sim$ 5.5 GeV$^2$. The distribution of the fundamental constituents, the quarks and gluons, is expected to be different in pions, kaons, and nucleons. The Electron-Ion Collider with an acceptance optimized for forward physics has the potential for accessing pion and kaon structure functions over a large kinematic region through the Sullivan process. Initial uncertainty projections have been carried out and suggest that such measurements are feasible for both pions and kaons.