Two pion diffractive electro-production

                          ZEUS Collaboration
 
                                Abstract

Diffractive electroproduction of pion pairs at HERA has been studied with 
the ZEUS detector. The analysis was carried out in the kinematic range of 
photon virtuality 2 < Q2 < 80 GeV2, gamma*p center-of-mass energy 40 < W < 
180 GeV and two-pion invariant mass 0.28 < M(pipi) < 2.3 GeV. The 
pi+pi- invariant-mass distribution was analyzed in terms of three 
isovector resonaces: rho, rho' and rho''. Masses and widths as well as 
relative amplitudes were obtained using a fit to the pion electromagnetic 
form factor. The Q2 dependence of the pion form factor was studied.