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{\bf EPS-HEP99} \\
{\bf Abstract \# 000} \\
{\bf Parallel sessions: 2,3} \\
{\bf Plenary sessions:  3}
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\abstractheader{ {\bf Measurement of Leading Proton and Neutron Production 
in Deep Inelastic Scattering at HERA  } \\ \\
H1 Collaboration, \\
DESY, Notkestr.85, D-22607 Hamburg, Germany
}

\abstractbody{
Deep--inelastic scattering events with a leading baryon have been detected
by the H1 experiment at HERA using a forward proton spectrometer and a
forward neutron calorimeter. Semi--inclusive cross sections have been
measured in the kinematic region
$2 \le Q^2 \le 50$~{\rm GeV}$^2$, $6\cdot 10^{-5} \le x \le 6\cdot 10^{-3}$
and baryon $p_T \le 200$~{\rm MeV}, for events with a final state proton with
energy $580 \le E^{\prime} \le 740$~{\rm GeV}, or a neutron with energy
$E^{\prime} \ge 160$~{\rm GeV}. The measurements are used to test production
models and factorization hypotheses. A Regge model of leading baryon
production which consists of pion, pomeron and secondary reggeon exchanges
gives an acceptable description of both semi--inclusive cross sections
in the region $0.7 \le E^{\prime} / E_p \le 0.9$, where $E_p$ is the
proton beam energy. The leading neutron data are used to estimate for
the first time the structure function of the pion at small Bjorken--$x$.
}

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{\bf Reference }\\
1. H1 Collaboration, C.~Adloff {\it et al}, 
DESY-98-169 / submitted to Eur. Phys. J. C 

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