Nucleon strangeness and unitarity

The strange-quark vector current form factors of the nucleon are analyzed within the framework of dispersion relations. Particular attention is paid to contributions made by $K\mathrm{K¯}$ intermediate states to the form factor spectral functions. It is shown that, when the $K\mathrm{K¯}\to N\mathrm{N¯}$ amplitude is evaluated in the Born approximation, the $K\mathrm{K¯}$ contributions are identical to those arising from a one-loop calculation and entail a serious violation of unitarity. The mean square strangeness radius and magnetic moment are evaluated by imposing unitarity bounds on the kaon-nucleon partial wave amplitudes. The impact of including the kaon’s strangeness vector current form factor in the dispersion integrals is also evaluated.