Exclusive electroproduction ofφmesons at 4.2 GeV

We studied the exclusive reaction $e\overrightarrow{p}{e}^{\prime }{p}^{\prime }\phi$ using the $\overrightarrow{\phi }{K}^{+}{K}^{-}$ decay mode. The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Our experiment covers the range in $Q^2$ from 0.7 to 2.2 ${\mathrm{GeV}}^2,$ and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of $\phi$ production on the proton. Our measurement shows the expected decrease of the t slope with the vector-meson formation time $c\Delta \tau$ below 2 fm. At $〈c\Delta \tau 〉=0.6\mathrm{}$ fm, we measure $b_{\phi }=2.27\mathrm{}\pm 0.42$ ${\mathrm{GeV}}^{-2}.$ The cross section dependence on W as $W^{0.2\pm 0.1}$ at $Q^2=1.3\mathrm{}$ ${\mathrm{GeV}}^2$ was determined by comparison with $\phi$ production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction.