No abstract

No abstract

No abstract

The exclusive production of ρ 0 mesons in deep inelastic electron-proton scattering has been studied using the ZEUS detector. Cross sections have been measured in the range 7 < Q 2 < 25 GeV 2 for γ * p centre of mass (c.m.) energies from 40 to 130 GeV. The γ * p → ρ 0 p cross section exhibits a Q −(4.2±0.8 +1.4 −0.5 ) dependence and both longitudinally and transversely polarised ρ 0 's are observed. The γ * p → ρ 0 p cross section rises strongly with increasing c.m. energy, when compared with NMC data at lower energy, which cannot be explained by production through soft pomeron exchange. The data are compared with perturbative QCD calculations where the rise in the cross section reflects the increase in the gluon density at low x. the gluon density at low x.

The exclusive electroproduction of ω mesons, ep → eωp, has been studied in the kinematic range 3 < Q 2 < 20 GeV 2 , 40 < W < 120 GeV and |t| < 0.6 GeV 2 with the ZEUS detector at HERA using an integrated luminosity of 37.7 pb −1 . The ω mesons were identified via the decay ω → π + π − π 0 . The exclusive cross section in the above kinematic region is σ ep→eωp = 0.108 ± 0.014(stat.) ± 0.026(syst.) nb. The reaction ep → eφp, φ → π + π − π 0 , has also been measured. The cross sections, as well as the ratios σ γ * p→ωp /σ γ * p→ρ 0 p and σ γ * p→ωp /σ γ * p→φp , are presented as a function of W and Q 2 . Thus, for the first time, the properties of ω electroproduction can be compared to those of ρ 0 , φ and J/ψ electroproduction at high W .The ZEUS Collaboration