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{\large\bf Measurement of Neutral and Charged Current Cross-Sections 
in Positron-Proton Collisions at Large Momentum Transfer 
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{H1 Collaboration}\\                            
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{\small \em DESY, Hamburg, Germany}\\[6mm]
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The inclusive single and double differential cross-sections for neutral
and charged current processes with  four-momentum transfer squared
$Q^2$ between $150$ and $30000$ \, GeV$^2$
are  measured in $e^+ p$ collisions 
with the H1 detector at HERA using the data taken in 1994$-$1997.
The data, which correspond to an integrated luminosity of $35.6 \
 {\rm pb}^{-1}$, 
amount to an increase in statistics by  an order of magnitude
with respect to the previously published results in this $Q^2$ domain.
Substantial 
extension in the kinematic range towards high $Q^2$ and $x$ has been
achieved, together with a reduction by a factor of more than two
of the systematic error of the measurements. 
The proton structure function $F_2(x,Q^2)$ is extracted and
the $Q^2$ evolution of the parton 
densities predicted by QCD is tested  at  
$x$-Bjorken values between $0.0032$ and $0.65$.
The $u$ and $d$ valence quark distributions are extracted at high $x$
No significant deviation from the
Standard Model has been found.
Predictions of the electroweak theory are confronted with the data, and 
their consistency is expressed by the observed mass of
 the $W$ boson obtained

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