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{\large\bf\boldmath Comparison of proton dissociative and elastic $\rho$ meson
electroproduction
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{H1 Collaboration}\\                            
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{\small \em DESY, Hamburg, Germany}\\[6mm]
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The production of $\rho$ mesons is studied in proton dissociative
and proton elastic electroproduction in the region of
squared momentum transfer $Q^2 > 1.5 {\rm\ GeV}^2$, using the H1 detector at
HERA.  The slopes of the squared transverse momentum, $P_t^2$, distributions
are measured as a function of $Q^2$ and the centre-of-mass energy $W$.  An
increase of the ratio of proton dissociative to elastic cross sections is
observed towards small $Q^2$. The evolution with $W$ is studied in several
$P_t^2$ and $Q^2$ intervals and the parameters of the pomeron
trajectory are measured. Shrinkage of the diffractive peak is observed for
$Q^2$ above a few ${\rm GeV}^2$. Angular distributions are studied as a
function of $P_t^2$ and $Q^2$ and significant deviation from the prediction
based on $s$-channel helicity conservation is observed.

 
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