Exclusive electroproduction of two pions at HERA

Abstract

The exclusive electroproduction of two pions in the mass range 0.4 <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 <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, {pipe}F(Mππ){pipe}, assuming that the studied mass range includes the contributions of the ρ, ρ′ and ρ″ vector-meson states. The masses and widths of the resonances were obtained and the Q2 dependence of the cross-section ratios σ(ρ′→ππ)/σ(ρ) and σ(ρ″→ππ)/σ(ρ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e+e-→π+π-. © 2012 The Author(s).