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\usepackage{lineno}                                                                                         
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\begin{document}  

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\begin{titlepage}

\noindent
Date:               \today \\
%%%Version:            1.2 \\
%%%Editors:            G.~Grindhammer (guenterg@mail.desy.de) \\ 
%%%                    R.~P\"oschl (poeschl@mail.desy.de) \\
%%%                    H.C.~Schultz-Coulon (coulon@mail.desy.de) \\
%%%Referees:           H.~Jung (jung@mail.desy.de) \\
%%%                    C.~Vallee (vallee@cppm.in2p3.fr) \\ 
\\
%%%Comments to editors and referees by {\bf 28-Mar-03}

%%%\vspace{2cm}

\begin{center}
\begin{Large}
  {\bf Dijet Production at low Bjorken-\boldmath{\em x} \\ 
       in Deep-Inelastic Scattering} 
       
\vspace{2cm}

H1 Collaboration

\end{Large}
\end{center}

\vspace{2cm}

\begin{abstract}
    
Dijet production in deep-inelastic $ep$ scattering is investigated in the regime
of low values of the Bjorken-variable~$x$ ($10^{-4} < x < 10^{-2}$) and low
four-momentum transfers~$Q^2$ ($5 < Q^2 < 100$~GeV$^2$).  The resulting dijet
cross sections are compared to perturbative QCD calculations in next-to-leading
order.  For most dijet variables studied, these calculations can provide a
reasonable description of the data over almost the full phase space region
covered, including the regime of very low $x$.  However, striking differences
are observed for events with small azimuthal jet separation, an observable
sensitive to the transverse momentum of the incoming gluon.  They are most
striking for the NLO calculations, but predictions based on the CCFM evolution
equation, which incorporate the ideas of $k_{t}$ factorization and the concept
of unintegrated parton distributions, and which should be particularly suited
for low $x$, also fail to describe the data.  A better but not good description
of the data is provided by various leading order Monte Carlo programs which
differ mainly in the way they model higher order effects through parton
cascades.

\end{abstract}

\vspace{1.5cm}

\begin{center}
%%%To be submitted to Eur.\,Phys.\,J.\,C
Preliminary results for DIS03, St.\,Petersburg
\end{center}

\end{titlepage}

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\begin{figure}[t]
\center
\epsfig{file=H1prelim-03-032.fig1.eps,width=0.95\textwidth}
\caption{
The triple differential inclusive dijet cross section in bins of Bjorken-$x$ and $Q^2$
as a function of the jet-$E^{\ast}_{T,{\rm max}}$ compared to NLO
QCD predictions using the CTEQ6M parton distribution functions. The data are shown together with
their statistical (inner error bars) and their statistical and systematic
error bars added in quadrature (outer error bars).  The NLO
predictions are corrected for hadronization effects which lower the
pure theoretical prediction by $\approx$ 10\%. The error band given
for the NLO predictions includes the
quadratic sum of hadronization and renormalization scale uncertainties.
}
\label{fig:ptmx} 
\end{figure}

\begin{figure}[t]
\center
\epsfig{file=H1prelim-03-032.fig2.eps,width=1.0\textwidth}
\caption{
The ratio of the measured triple differential inclusive dijet cross section
as a function of the jet-$E^{\ast}_{T,{\rm max}}$  and the NLO QCD
predictions using the CTEQ6M parton distribution functions. The
uncertainty of the theoretical prediction is indicated by the
band. The contributions from the renormalization scale uncertainties
and the hadronization corrections are added in quadrature.
}
\label{fig:ptmxdt} 
\end{figure}


\begin{figure}[t]
\center
\epsfig{file= H1prelim-03-032.fig3.eps,width=0.95\textwidth}
\caption{
The triple differential inclusive dijet cross section in bins of Bjorken-$x$ and $Q^2$
as a function  of the distance $|\Delta\eta^{\ast}|$ between the dijets compared to NLO
QCD predictions using the CTEQ6M parton distribution functions. The data are shown together with
their statistical (inner error bars) and their statistical and systematic
error bars added in quadrature (outer error bars).  The NLO
predictions are corrected for hadronization effects which lower the
pure theoretical prediction by $\approx$ 10\%. The error band given
for the NLO predictions includes the
quadratic sum of hadronization and renormalization scale uncertainties.
}
\label{fig:etajet} 
\end{figure}

\begin{figure}[t]
\center
\epsfig{file= H1prelim-03-032.fig4.eps,width=1.0\textwidth}
\caption{
The ratio of the measured triple differential inclusive dijet cross section
as a function of the distance $|\Delta\eta^{\ast}|$ between the dijets  and the NLO QCD
predictions using the CTEQ6M parton distribution functions. The
uncertainty of the theoretical prediction is indicated by the
band. The contributions from the renormalization scale uncertainties
and the hadronization corrections are added in quadrature.
}
\label{fig:etajdt} 
\end{figure}




\begin{figure}[t]
\center
\epsfig{file= H1prelim-03-032.fig5.eps,width=0.98\textwidth} 
\caption{
Ratio of jets separated by less than $120^{\rm o}$ in azimuthal angle to
all dijet events as function of Bjorken-$x$ and \qsq, compared to NLO QCD
predictions using the CTEQ6M parton distribution functions and LO QCD
models with $k_{T}$-ordered (RAPGAP) and with $k_{T}$-unordered (ARIADNE)
parton showers and full hadronization.  The data are shown together with
their statistical (inner error bars) and their statistical and systematic
error bars added in quadrature (outer error bars).  The NLO QCD predictions
are represented as error bands including the
quadratic sum of hadronization and renormalization scale uncertainties.
}
\label{fig:ssjet120} 
\end{figure}

\begin{figure}[t]
\center \epsfig{file= H1prelim-03-032.fig6.eps,width=1.0\textwidth}
\caption{ 
Ratio of jets separated by less than $120^{\rm o}$ in azimuthal angle to
all dijet events as function of Bjorken-$x$ and $Q^2$. The data are compared 
to predictions from the RAPGAP Monte Carlo,
which allows to include direct alone (full line) and direct and resolved
contributions (dashed line) of the virtual photon.
The data are shown together with their statistical (inner error bars) and their statistical
and systematic error bars added in quadrature (outer error bars).
}
\label{fig:ssjet120rg} 
\end{figure}

\begin{figure}[t]
\center \epsfig{file= H1prelim-03-032.fig7.eps,width=1.0\textwidth}
\caption{ 
Ratio of jets separated by less than $120^{\rm o}$ in azimuthal angle to
all dijet events as function of Bjorken-$x$ and $Q^2$. The data are
compared to predictions from a QCD model
implementing the CCFM evolution (CASCADE) and using the CCFM (full line)
and KMR (dashed line) $k_{t}$-unintegrated gluon distribution functions.
The data are shown
together with their statistical (inner error bars) and their statistical
and systematic error bars added in quadrature (outer error bars).
}
\label{fig:ssjet120casc} 
\end{figure}

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