2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/171291Exclusive production of $ϕ$ mesons on hydrogen and deuterium targets is studied in the HERMES kinematic region $1 < Q^{2} < 7$ GeV$^2$ and $3.0 < W < 6.3$ GeV. Spin density matrix elements and their $Q^{2}$ and $t$ dependences are presented. These data are consistent with s-channel helicity conservation in exclusive $ϕ$ meson production. No significant evidence for the contribution of unnatural-parity-exchange amplitudes is found.6 pages, 4 figures, Proceedings of DIS 2008, London, UK, April 7-11, 2008;High Energy Physics - Experimenttext