Electroproduction of the Phi(1020) Vector Meson at 4 GeV
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We studied the reaction ep -> e'p'phi with a 4.2 GeV incident electron beam in the region of the electroproduction variables Q2 from 0.7 to 2.2 GeV2 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 Q2 and Delta-Tau in phi vector meson production. We find that the width of the forward phi-meson diffraction peak increases rapidly as the interaction time decreases below cDelta-Tau of 1 fm. Within a simple optical model framework, the data show that phi meson has a smaller size than the rho. The measured phi cross-section dependence on Q2 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 ss-bar-knockout model predictions. From the angular distribution of the decay phi -> K+K-, assuming the s-channel helicity conservation, we extracted the longitudinal-to-transverse cross-section ratio, R, and Vector Meson Dominance scaling parameter, xi2, which are consistent with the previous measurements and the model expectations.
- Doctoral Dissertations