Unitary and analytic model of nucleon EM structure, the puzzle with JLab proton polarization data and new insight into proton charge distribution

摘要

The Unitary and analytic model of nucleon electromagnetic structure,describing all existing nucleon form factor data, is briefly reviewed. Then inthe framework of this model the problem of inconsistency of older protonelectric form factor data in space-like region (obtained from $% e^{-}p\toe^{-}p$ process by the Rosenbluth technique) with recent Jefferson Lab data onthe ratio $G_{Ep}(t)/G_{Mp}(t)$ (measured in precise polarization$\overrightarrow{e}^{-}p\to e^{-}\overrightarrow{p}$ experiment) is suggestedto be solved in favour of the latter data which, however, unlike older datacause an existence of the form factor zero, i.e. a difraction minimum in$|G_{Ep}(t)|$ around $t=-Q^{2}=-13$GeV$^{2}$. The new behaviour of $G_{Ep}(t)$with the zero gives modified proton charge distribution with enlarged value ofthe mean square charge radius.