Energy check for the Form Factor at chi0.



1) weighting the energies with luminosity in tab. of
   the chi0 paper we find:

   E=3410 MeV with L=32.785  (s=11.63 GeV^2 and not 11.61)

   the value of energy is the same shown in the Form Factor
   draft, while there is a difference in the integrated luminosity
   because for the Form Factor analisys we also used the RUN 5520 
   with E=3405.0 MeV and L=0.076 pb^-1, which is not used in the chi0
   analisys.
   Infact the difference between the integrated luminosity at chi0 in 
   FF draft and that in the chi0 paper is the luminosity of the RUN 5520.

2) About the invariant mass distribution of preselected sample at psip, 
   we have to say that the distribution of J/psiX events (horizontal-lines) 
   is just a little bit grater than the white-distribution, because for 
   J/psiX events we toke into account the efficiency for this selection.

   It seems that this behaviour doesn't make sense, but if take into account 
   the errors white and horizontal-distribution is "compatible".

   There was a little wrong thing in the calculation of the J/psiX efficiency 
   (which was 87%), with correct value (about 92%) we obtain the new 
   distribution shown in the 3rd version of the Form Factor draft. 
   This new value of J/psiX efficiency doesn't affect the final results of 
   the cross section and form factor.