Аннотация:Elastic ρ0 photoproduction has been measured using the ZEUS detector at HERA. Untagged photoproduction events from ep interactions were used to measure the reaction γp → ρ0p (ρ0 → π+π−) at photon-proton centre-of-mass energies between 60 and 80 GeV and |t| < 0.5 GeV2, where t is the square of the four-momentum transferred at the proton vertex. The differential cross section dσ/dMππ, where Mππ is the invariant mass of the two pions, and the integrated cross section, σγp→ρ0p, are presented; the latter was measured to be 14.7 ± 0.4 (stat.) ± 2.4 (syst.) μb. The differential cross section dσ/dt has an approximately exponential shape; a fit of the type A′t exp (−b′t|t| + c′tt2) yields a t-slope b′t = 9.9 ± 1.2 (stat.) ± 1.4 (syst.) μb. The results, when compared to low energy data, show a weak energy dependence of both σγp→ρ0p and of the t-slope. The ρ0 is produced predominantly with transverse polarisation, demonstrating that s-channel helicity conservation holds at these energies.