Elastic rho production at HERA

Abstract

Results on elastic electroproduction of rho mesons are presented for a photon virtuality in the range 1 < Q^2 < 60 GeV^2 and for a hadronic centre of mass energy in the range 30 < W < 140 GeV. The shape of the (pi pi) mass distribution is discussed and measurements of the cross section dependences on Q^2, W and t (the four-momentum transfer squared to the proton) are presented. The full set of rho spin density matrix elements is measured, providing information on the rho meson and on the photon polarisation states. In particular, the ratio R of longitudinal to transverse gamma^*p cross section is determined.

Comments: 3 pages, 2 figures Contribution to the proceedings of the VII International Workshop on Deep Inelastic Scattering and QCD (DIS99)