Ratios of helicity amplitudes for exclusive ρ0 electroproduction

Abstract

Exclusive ρ0-meson electroproduction is studied in the HERMES experiment, using a 27.6 GeV longitudinally polarized electron/positron beam and unpolarized hydrogen and deuterium targets in the kinematic region 0.5 GeV2 < W < 6.3 GeV, and -t′ < 0.4 GeV2. Real and imaginary parts of the ratios of the natural-parity-exchange helicity amplitudes T11 (γT* → ρT), T01 (γT* → ρL), T10 (γL* → ρT) and T1-1 (γ-T* → ρT) to T00 (γL* → ρL) are extracted from the data. For the unnatural-parity-exchange amplitude U11, the ratio {pipe}U11/T00{pipe} is obtained. The Q2 and t′ dependences of these ratios are presented and compared with perturbative QCD predictions. © 2011 The Author(s).