STUDY OF ELECTROMAGNETIC PROPERTIES OF MESONS

Abstract

In the framework of vector meson dominance (VMD) model the electromagnetic (EM) monopole form factor (FF) of charged pions F7t (q2) is developed and generalized. The generali::ed formula which contains three parameters is used to fit the results of the direct elastic pion-electron sea ttering to extract the fundamental properties of pions in the three regions of four momentum transfer squared 0.0138 (GeV/c)2 q2 ;s; 0.0353 (GeV/c)2 , 0.0317 (GeV/c)2 q 2 0.0705 (GeV/c)2 and 0.039 (GeV/c)2 q2 0.092 (GeV/c)2.

The proposed generalized formula gives not only a non-linear relation between F7t2 (q2 ) and q2 but also provides the finiteness of dF7t/dq 2 for q2 0 and the correct normalization F7t (0) = 1.

A computer simulation iterative search program was done to parameterize the best free parameters in a group of sets yielding the results:

The electromagnetic root mean square radius of the

pion is <r2

= 0.29 fm

- v-

The electromagnetic mass difference between the charged and neutral pion is D7t = mn± - mno = 4.4847 MeV. The pionic 2P 18 transition energy shifts caused by strong n-- nucleus interaction was also calculated by using our proposed electromagnetic form factor.

Our theoretical results are in good agreement with the recent experimental values.

The advantage of he proposed generalized formula is its · independence of previous n10dels and also the integrals which appeared in calculating the electromagnetic mass difference were evaluated analytically. Our generalized forn1ula f<?r the form factor was found to deviate significantly from the pole fit but is consistent with the recent calculations based on the meson exchange model of the nn system.