Exclusive $ρ^{0}$ , $ω$ , and $φ$ electroproduction

We have measured exclusive

ρ^{0}

ω

, and

φ

meson electroproduction at the Cornell Wilson Synchrotron. The final

ρ^{0}

data sample included 4637 four-constraint

e + p \to e + π^{+} + π^{-} + p

events, with incident energy

E = 11.5

GeV and electroproduction variables

Q^{2}

and

W

in the region

0.7 < Q^{2} < 4

{GeV}^{2}

and

1.9 < W < 4

GeV. We find that the width of the forward

ρ^{0}

diffraction peak increases rapidly as the lifetime of the intermediate hadron states decreases below

c Δ τ = 1

fm and that the peak is wider for longitudinal

ρ^{0}

than it is for transverse

ρ^{0}

. The longitudinal-transverse cross-section ratio

R_{p} = \frac{σ_{L}}{σ_{T}}

, obtained assuming

s

-channel helicity conservation, becomes constant at high

Q^{2}

. At fixed

W

the diffractive vector-meson-dominance (VMD) model reproduces the

Q^{2}

dependence of our cross section,

σ = (σ_{T} + ε σ_{L})

, but is is not able to account for the rapid decrease in the cross section with increasing

W

we observe. We find that

\frac{σ_{ω}}{σ_{ρ}}

depends on

W

but is independent of

Q^{2}

for

0.7 < Q^{2} < 3

{GeV}^{2}

and

2.2 < W < 3.7

GeV. However,

σ_{ω}

is substantially larger than the diffractive VMD cross section. Our results for

σ_{φ}

are consistent with the

Q^{2}

dependence of the diffractive VMD model for

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Exclusiveρ0,ω, andφelectroproduction