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{\bf Abstract Registration Number 570} \\
{\bf Parallel sessions: 5,3} \\
{\bf Plenary sessions: 7,5}
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\abstractheader{\bf Double Diffraction Dissociation at large $|t|$ \\
H1 Collaboration, DESY}

\abstractbody{
The double diffractive dissociative cross section 
$\gamma p \rightarrow XY$ 
is measured at large 4-momentum transfer squared $|t|$. The systems $X$ and 
$Y$ are separated by the largest rapidity gap in the event with all 
particles on the photon side of the gap ascribed to the system $X$.
Diffractive events are then characterised by $M_{X}, M_{Y} \ll W$, 
where $W$ is the $\gamma p$ centre of mass
energy, for the case where $M_Y$ is small.
Cross sections are measured differentially in 
$x_{_{I\!\!P}} = (M_X^2 - t) / W^2$.
In the range $0.001 < x_{_{I\!\!P}} < 0.01$, the shapes of the 
measured $x_{_{I\!\!P}}$ distributions are
compared to predictions for standard photoproduction processes and to a
model based on the exchange of a strongly interacting 
colour singlet object at large $|t|$.
}

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