Electromagnetic Structure of Nucleon

Akira Kanazawa, Masahiro Haruyama
1969 Progress of theoretical physics  
In this note we present a simple model for the nucleon electromagnetic form factor, which has a form similar to the pion form factor derived by H. Sugawara,l> who used a spurion formalism in applying the Veneziano formula to the vertex. The model surprisingly well reproduces the experimental data known up to date. The spurion technique results in a form factor with the recent attempts of similar approach,2>,a>,4> where an infinite series of poles is summed up in quite an intuitive way. The
more » ... on formalism 1 > suggests that the form factor should have a form r (1 -a)/ F(n-a) accompanied with possible satellite terms. Here a is a vector meson trajectory with appropriate quantum numbers, i.e. the p trajectory for the isovector part and the (j) and i f> trajectories for the isoscalar part. The guiding principles in this note to build up the model are i) the simplicity, ii) the super-convergence and iii) to satisfy the requirements imposed by the experiment at low energy limit. The requirements are 5 > where G(t) is Sachs' electric or magnetic form factor as an analytic function of t, the momentum transfer squared in unit of (GeV/c)Z. The superscript indicates the isospin structure of the form factor. G is the derivative of G with respect to t. We choose n=3 so that G(t) behaves like r 2 in a large momentum transfer region, and we take account of only leading terms for (j) and r/J contributions, while we retain the first satellite term as well as the leading one for p. For the trajectory functions we simply assume Thus our form factors contain eight free parameters as a whole, which can be fixed by imposing the condition (1). The results are given explicitly by The proton and the neutron form factors corresponding to those of Eq. (3) are figured out in Figs. 1-5, with the experimental data 5 > available up to date. The fit is surprisingly good.
doi:10.1143/ptp.42.1487 fatcat:nbabi4gtbbhsvpczwttuynamji