Electroproduction of the φ ( 1020 ) Vector Meson

We studied the reaction ep → e′p′φ with a 4.2 GeV incident electron beam in the region of the electroproduction variables Q from 0.7 to 2.2 GeV and W from 2.0 to 2.6 GeV. The data were taken and analyzed at the Thomas Jefferson National Accelerator Facility. For the first time, we observe the expected t-slope dependence on Q and ∆τ in φ vector meson production. We find that the width of the forward φ-meson diffraction peak increases rapidly as the interaction time decreases below c∆τ ≈ 1 fm. Within a simple optical model framework, the data show that φ meson has a smaller size than the ρ. The measured φ cross-section dependence on Q is in a good agreement with previous measurements and well-described by the phenomenological Pomeron-exchange model. Our cross-section data do not favor the standard Vector Meson Dominance and ss̄-knockout model predictions. From the angular distribution of the decay φ → K+K−, assuming the s-channel helicity conservation, we extracted the longitudinal-to-transverse cross-section ratio, R, and Vector Meson Dominance scaling parameter, ξ, which are consistent with the previous measurements and the model expectations. This work was supported by the TJNAF and SURA Graduate Student Fellowship Program.