Low Q² results from the PionLT and KaonLT experiments at Jefferson Lab

Being the lightest bound states in the hadron spectrum, the pion and kaon mesons are essential to understand the strong interaction in the non-perturbative domain of QCD. They are pseudo-Goldstone bosons that originate from the spontaneous breaking of chiral symmetry, and provide a novel perspective on the dynamical mass creation and confinement mechanisms in QCD. The measurement of a key structure observable of these mesons, their electric form factors, is challenging. For very low photon virtuality, Q²<0.3 GeV², they have been determined via inverse kinematics experiments with π⁺ and K^- beams incident on atomic electrons. Measurements at higher Q², where the most interesting QCD questions lie, require forward kinematics. Since pion and kaon targets are not possible, the Sullivan process is used, where the electron scatters from the virtual meson cloud of the nucleon via the exclusive ep→e'π⁺n and ep→e'K⁺Λ reactions above the hadronic resonance region. A model is then used to infer the meson form factors from the experimental data.

The KaonLT and PionLT experiments at Jefferson Lab are intended to greatly increase our knowledge of the charged pion and kaon form factors by producing a cross section database for both reactions, separated according to the L/T/LT/TT polarizations of the virtual γ, over a wide kinematic range. Both experiments include a variety of tests of the Sullivan method, of which one is measurements at Q²=0.375-0.5 GeV², coming close to the limit of the inverse kinematic form factor results. Preliminary results from these measurements will be presented.