Abstract: | The exclusive electroproduction of two pions in the mass range 0.4 <
M{pi}{pi} < 2.5 GeV has been studied with the ZEUS detector at HERA using an
integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic
range of 2 < Q2 < 80 GeV2, 32 < W < 180 GeV and |t| < 0.6 GeV2, where Q2 is the
photon virtuality, W is the photon-proton centre-of-mass energy and t is the
squared four-momentum transfer at the proton vertex. The two-pion
invariant-mass distribution is interpreted in terms of the pion electromagnetic
form factor, |F(M{pi}{pi})|, assuming that the studied mass range includes
the contributions of the {
ho}, {
ho}’ and {
ho}" vector-meson states. The
masses and widths of the resonances were obtained and the Q2 dependence of the
cross-section ratios {sigma}({
ho}’
ightarrow {pi}{pi})/{sigma}({
ho})
and {sigma}({
ho}"
ightarrow {pi}{pi})/{sigma}({
ho}) was extracted.
The pion form factor obtained in the present analysis is compared to that
obtained in e+e-
ightarrow {pi}+{pi}-. |