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\begin{document}

\pagestyle{empty}
\begin{titlepage}

\noindent
\begin{center}
\begin{small}
\begin{tabular}{llrr}
Submitted to & & &
\epsfig{file=/h1/www/images/H1logo_bw_small.epsi
,width=2.cm} \\[.2em] \hline
\multicolumn{4}{l}{{\bf
                32nd International Conference 
                on High Energy Physics, ICHEP04},
                August~16,~2004,~Beijing} \\
                 & Abstract:        & {\bf 5-0165}    &\\
                 & Parallel Session & {\bf 5}   &\\ \hline
 & \multicolumn{3}{r}{\footnotesize {\it
    www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em]
\end{tabular}
\end{small}
\end{center}
\vspace*{2cm}

\begin{center}
  \Large
  {\bf 
    
    Measurement of Beauty Production \\
    in Deep Inelastic Scattering \\ 
    at HERA}

  \vspace*{1cm}
    {\Large H1 Collaboration}

  \vspace*{1cm}
 
\end{center}

\begin{abstract}

\noindent

Differential measurements of beauty electroproduction cross sections
in $ep$ collisions performed with the H1 detector at HERA are presented. 
%
The data were collected at an $ep$
centre-of-mass energy of 319 GeV in the years 1999-2000 
and correspond to an integrated luminosity of 50 pb$^{-1}$.
%
Events are selected by requiring at least one high-transverse momentum
jet in the Breit frame with $p^*_{t,jet}>6$ GeV, jet pseudorapidity 
$|\eta^{jet}|<2.5$ and a muon associated to the jet
with $-0.75<\eta^{\mu}<1.15$ and $p_t^{\mu}>2.5$ GeV.
%
Both the lifetime signature and the large mass of $b$-flavoured hadrons
are exploited to determine the fraction of events 
in the sample containing beauty.
%
Differential jet-muon cross sections are measured in the region 
of photon virtuality
\mbox{$2<Q^2<100$ GeV$^2$} and inelasticity $0.1<y<0.7$.
%
%The visible dijet-muon production cross section is measured to be 
%$ \sigma_{vis}(ep \rightarrow e b\bar{b}X 
%\rightarrow e jj\mu X) = (42.5 \pm 3.4 (stat.) \pm 8.9 (sys.)) {\rm pb}.
%$
%
The results are compared with different Monte Carlo models and
with calculations in NLO perturbative QCD.

\end{abstract}

%  \vspace*{1cm}
 
%\centerline{Prepared for DIS 2004, Strbske Pleso, Slovakia}

\end{titlepage}

\pagestyle{plain}

\section{Introduction}
%
This paper presents a measurement of 
open beauty production in $ep$ collisions
in deep inelastic scattering 
where the photon virtuality $Q^2 > 2$ GeV$^2$.
%
$b$-quark production is an interesting
testing ground for perturbative QCD (pQCD)
since the large mass of the $b$-quark provides a hard scale.
Towards larger $Q^2$ and/or $p_t$ the interplay between
the different hard scales can be investigated.

Early measurements, 
both in photoproduction~\cite{Adloff:1999nr,h1bprelim,Breitweg:2000nz}
and in deep inelastic scattering, 
indicated that the beauty production cross section 
lies significantly above the next-to-leading order QCD expectations.
Similar observations have been made in hadron-hadron collisions~\cite{hadronb},
and also in two-photon interactions~\cite{ggb}.
%
While for some of the above measurements large extrapolations
beyond the measurable kinematic range were performed using 
Monte Carlo simulations, the
more recent measurements reported visible cross sections,
$
e^+p \rightarrow e^+ b\bar{b} X \rightarrow e^+ + jets + \mu^{\pm} + X,
$
\cite{h1bprel2003,Chekanov:2003si}
within the accessible detector acceptance.
To compare with next-to-leading order
perturbation theory the theoretical calculations
were interfaced with parametrized $b$-quark fragmentation 
and muon decay spectra in order to impose the 
same kinematic constraints as for the measurements.
Comparisons between the measured and calculated
visible cross sections then showed reasonable agreement
between data and theory.


In this paper a new measurement of beauty production
in $ep$ scattering is presented. 
%
%using more statistics and
%a modified selection procedure.
%
%
Events with at least one jet and a muon in the final state are used
to measure the beauty production cross section
$
e^+p \rightarrow e^+ b\bar{b} X \rightarrow e^+ + jet + \mu^{\pm} + X.
$
%
The cross section is measured 
differentially as a function of the photon virtuality 
$Q^2$, the Bjorken scaling variable $x=Q^2/sy$ and
the transverse momentum of the $b$-quark jet in the Breit 
frame, $p^*_t,jet$. 
Here $s$ is the $ep$ center of mass energy and $y$ the
fractional energy of the exchanged photon in the proton
rest-frame. 
The differential cross section is also measured as a function
of the transverse momentum of the $b$-quark jet in the Breit frame.

%
For the measurement both the lifetime signature and 
the large mass of $b$-flavoured hadrons
are used to determine the fraction of beauty quark events in the sample.
The fraction of $b$-quark events in the final sample is determined 
by a fit to the two-dimensional distribution of the \ptrel and \del
observables in the data with adjustable fractions of beauty,
charm and light-quark components, the shapes of which are 
taken from Monte Carlo (MC) simulations.
The experimental procedure follows closely the one
described in detail in 
\cite{h1bprel2003}.
%
This paper is organised as follows:
The event selection is described in section \ref{sec:sel}.
The Monte Carlo simulations and data sets used to model the signal
and background components of the data are 
described in section \ref{sec:mc}. In section \ref{sec:fit}
the signal determination observables and procedure are outlined.
In section \ref{sec:nlo} the calculations in perturbative QCD 
performed at next-to-leading order are explained.
% 
The measured cross sections are presented in section \ref{sec:results}
and compared with predictions from Monte Carlo simulations and pQCD.
%

\section{Event Selection}
\label{sec:sel}

The H1 Experiment is described in detail 
in \cite{Abt:1997xv,cst,Nicholls:1996di}.
The data for this analysis were recorded
in 1999 and 2000 and correspond
to an integrated luminosity of $50\,$pb$^{-1}$.
%
The events were triggered by requiring the coincidence of signals 
from the scattered electron in the calorimeter, and tracks in 
the central drift chambers (CJC)
and the multi-wire proportional chambers. 
%
Events are selected by requiring that there be at least one high 
energetic ($E>8$ GeV) 
electromagnetic cluster in the backward calorimeter.
The accepted range of negative four-momentum
transfer squared is restricted to $2<Q^2<100$ GeV$^2$.  
An inelasticity  cut \mbox{0.1 $<y<$ 0.7} is applied, 
where $y$ is calculated using the Sigma method~\cite{basslerbernardi}, 
which reduces sensitivity of the kinematic reconstruction
to QED-radiation off the incoming beam electron.
%
Jets are reconstructed in the Breit frame 
using the inclusive $k_t$ algorithm~\cite{kt} 
with radius $R=1$ in the $\eta$-$\phi$ plane.
% 
The $E_T$-recombination scheme is applied 
giving massless jets.
%which leads to massless jets.
% 
The selection requires at least one jet with 
transverse energy in the Breit frame of $p^*_{t,jet}>6$ GeV,
which contains a muon candidate.
% 
Muons are identified as tracks in the barrel part of 
the instrumented iron return yoke, linked to the drift chamber track
with a link-probability larger than 5\%,
and are required to have a transverse momentum of 
$p_t^{\mu}>2.5$ GeV.
The iron barrel acceptance corresponds to polar 
angles $35^{\circ} < \theta (\mu)<130^{\circ}$.
%
The measurement of the impact parameter is facilitated
by the high precision tracking made possible with
the H1 central silicon tracker (CST).
%
At least two CST-$r$-$\phi$-hits must be associated with the 
muon candidate track, measured in the central drift chambers.  
The combined CJC-CST $r$-$\phi$-track fit probability 
must exceed 10\%.  
%
The final event sample consists of 780 events.

%
\section{Monte Carlo Simulations and Control Data Samples}
\label{sec:mc}
%
Monte Carlo event samples for the processes 
$ep\ra e\bbb X$, $ep\ra e\ccb X$ and light quark production
are generated using the RAPGAP program~\cite{Jung:1993gf}
which is based on leading order QCD and parton showers.  
%
In RAPGAP the charm and beauty quarks are produced via 
boson-gluon fusion (massive approach). RAPGAP implements 
QED radiation effects.
The light quark sample is used to simulate
the background from fake muons, i.e. hadrons misidentified as muons, 
and decays of light mesons into muons.
%
The CTEQ5L~\cite{cteq5l} parton densities are used
% hep-ph/9903282 
for the proton.
%
The programs PYTHIA
\cite{PYTHIA} and CASCADE \cite{Jung:casc} are
used for cross checks. 
PYTHIA simulates direct and resolved photon processes and 
also includes excitation processes, in
which one heavy quark ($c$ or $b$) originates from the
resolved photon or the proton. 
PYTHIA is run in an inclusive mode and generates all the above 
processes using massless matrix elements.
CASCADE is a Monte Carlo generator which
implements the CCFM parton evolution equation  
\cite{ccfm}.
The Monte Carlo simulation programs have been checked to
accurately describe the detector resolutions, efficiencies 
and acceptances.
%
%-------------------------------------------------------
\section{Predictions Based on QCD NLO Calculations}
\label{sec:nlo}

The program HVQDIS for NLO calculations by 
B.W.Harris and J.Smith \cite{Harris:1995dv} was modified to 
facilitate the comparison of the calculation with the 
visible cross sections in the experimentally accessible kinematic range.
The outgoing partons ($b$-quark, $\bar{b}$ quark and the gluon) are combined
into jets using the inclusive $k_t$ jet-algorithm (in the $E_t$-scheme).
The $b$-quark is then fragmented to a $B$-Hadron using the 
Peterson fragmentation function \cite{peterson}
with a fragmentation parameter
$\epsilon = 0.0033$. The $B$-Hadron subsequently decays into a muon.
%
The muon spectrum takes both direct and cascade decays via charm into account.

The calculation is performed for a $b$-quark mass of 4.75 GeV with
factorisation and renormalisation scales 
defined as 
$\mu_R = \mu_F = \sqrt{Q^2 + 4 m_b^2}$. 
%
For the structure functions the DIS-scheme parametrisations
CTEQ5F3 \cite{cteq5l} for the proton is used.
Systematic errors are 
estimated by varying the $b$-quark mass up and
down by 0.25 GeV and  
$\mu_R$ and $\mu_F$ up and down by factors
of two.
%
The systematic error is estimated by simultaneous
variation of the $b$-quark mass, 
$\mu_R$ = $\mu_F$ 
up and down respectively by 0.25 GeV and a factor two. 
The cross section variation when using
other proton structure functions such as GRV98 or CTEQ4F3 
is less than 8\% in all regions of the measurement.
The uncertainty due to variations of the fragmentation parameter 
$\epsilon$ by $25\%$ is below 3\%.
This leads to a total uncertainty of \mbox{+13\% -20\%.}

The obtained parton level cross sections are corrected to the hadron level
using the RAPGAP Monte Carlo generator. The corrections are 
on the level of $20\%$ in all bins of the measurement
decreasing towards larger $p_{t,jet}$. 
The shape comparison of the RAPGAP Monte Carlo with HVQDIS calculation
gives a good description of the muon and the jet variables.
 
 
\section{Determination of Signal and Background Components}
\label{sec:fit}
%
The two observables $\delta$ and $p_T^{rel}$
are used to determine the fraction of the
beauty component in the data.
%
Decays of long-lived particles are signalled by positive 
impact parameters, whereas the finite track resolution yields 
a symmetric distribution centered on zero.
%
The transverse momentum \ptrel of the muon track is calculated 
relative to the momentum of the associated jet
%jet with which it is associated 
after subtraction of the muon momentum.
%
The details of the signal and background determination have been 
described in \cite{h1bprel2003}.

%
The two observables $\delta$ and $p_T^{rel}$
are complementary in the discrimination
of the beauty component in the data
from the background sources and
the fraction of beauty events in the data is determined from
a combined fit to the two-dimensional distribution of
$\delta$ and $p_T^{rel}$. 
%
The fit uses the shapes 
of the distributions
of beauty, charm and light quark events from the RAPGAP Monte
Carlo simulation.  
%
The relative weights of all three components are adjusted 
such that the likelihood is maximized.
%
The overall normalisation of the summed contributions
is adjusted to match the data.
%
%B FITRES( 8) = 31.084
%C FITRES( 9) = 49.9303
%F FITRES(10) = 18.9956
%B FITRES(11) = 3.74023
%C FITRES(12) = 7.23291
%F FITRES(13) = 6.98796
%
The fit yields a sample composition of 
$f_b = (31.1 \pm 3.7)\,\%$ (beauty),
$f_c = (49.9 \pm 7.2)\,\%$ (charm) and
$f_{uds} = (19.0 \pm 7.0)\,\%$ (uds). 
Here the errors refer to the statistical
uncertainties.
%

The quality of the description of the data sample
using the fractions obtained with the two-dimensional 
fit is demonstrated using the one-dimensional \del and \ptrel projections.
%
Figure~\ref{fig:signal-delta} shows the measured 
impact parameter distribution in the data together 
with histograms indicating the contributions from 
$b$-production and from the $c$ and $uds$ backgrounds using the relative
fractions obtained in the two-dimensional fit.
%
% To get to the following numbers 
% do the following
% run mfinal and stop after delta fit and then do:
% fitd3 10000 20000 30000 60000 1 2 0 0 0 
%  FITRES( 1) = 10000
%  FITRES( 2) = 20000
%  FITRES( 3) = 30000
%  FITRES( 4) = 1.06E+06
%  FITRES( 5) = 1
%  FITRES( 6) = 2
%  FITRES( 7) = 0
%  FITRES( 8) = 26.1864
%  FITRES( 9) = 53.2399
%  FITRES(10) = 20.5737
%  FITRES(11) = 6.28378
%  FITRES(12) = 17.1432
%  FITRES(13) = 14.0909
%
The data are well described by the sum of the 
estimated contributions.
%
%As a cross check a free fit to the \del distribution alone
%yields a sample composition of
%$f_b = (25.4 \pm 6.4)\%$,
%$f_c = (59.4 \pm 16.8)\%$
%and $f_{uds} = (15.1 \pm 13.5)\%$
%in good agreement with the above fit results.
%
In figure~\ref{fig:signal-ptrel} the observed 
$p_t^{rel}$ distribution is shown.
The histogram represents the summed contributions from 
$b$-production and from the backgrounds, using
the fractions determined above.
%
As for the impact parameter, also 
the distribution of \ptrel is 
well described by the sum of the
estimated contributions.

The $b$-fraction can be enriched significantly by
cuts in the distributions of \ptrel and/or \del.
Figures~\ref{fig:signal-highp-delta} and \ref{fig:signal-highp-ptrel}
show the result for  
regions of high $b$-purity, i.e.~\ptrel $ >1.2$ GeV and 
\del $>0.01$ cm, respectively.
%
Also these high $b$-purity data are reasonably well described 
with the estimated contributions, derived from the results of the
above two-dimensional fit. 
% 
%
%As a cross check a free fit is performed 
%to the \ptrel distribution alone. 
%
%The shapes of the \ptrel distributions
%for charm and light quark events are very similar 
%and
%consequently the relative contribution of these two 
%components cannot be precisely determined from this fit to the \ptrel 
%distribution alone.
%
%Hence the charm and light quark components 
%and hence these two contributions are combined
%using the prediction from the RAPGAP Monte Carlo simulation.
%
%The fit yields a sample composition of
%  
%  h/file 1 plotsfinal/hist-30622-110103-1230-b1690-7-2comp-lsq2.hbook  
%  fitd3 10001 20001 30001 0 1 2 0 0 0 0 
% FITRES( 1) = 10001
% FITRES( 2) = 20001
% FITRES( 3) = 30001
% FITRES( 4) = 0
% FITRES( 5) = 1
% FITRES( 6) = 2
% FITRES( 7) = 0
% FITRES( 8) = 28.8383
% FITRES( 9) = 71.1611
% FITRES(10) = 0
% FITRES(11) = 2.78049
% FITRES(12) = 3.22386
% FITRES(13) = 0
% FITRES(14) = 28.127
% FITRES(15) = 24 
%
%$f_b = (xxx \pm xxx)\%$,
%$f_c + f_{uds} = (xxx \pm xxx)\%$,
%
%also in good agreement with the above fit results {(\sf still to be done)}.
%
% chisquare is 42/24
%
%The fit gives a good description of the data.
%
% HIGH PURITY STUFF, TAKEN OUT
%
%At \ptrel $> 1.5$ GeV the beauty component is the dominant component.
%
%Figure~\ref{fig:high-purity} shows the observed 
%distributions of the impact parameter $\delta$ and
%the relative transverse muon momentum $p_t^{rel}$ 
%with cuts of $p_t^{rel}>1.4$ GeV and $\delta>0.03$ cm, respectively,
%thus enhancing the fraction of $b$ events.
%
%To further elucidate the consistency of the two observables
%$\delta$ and $p_T^{rel}$ one can enrich the beauty component
%in the events by restricting the range of one variable and then studying
%the distribution of the other quantity.
%
%Figure~\ref{fig:high-purity-delta} 
%shows the observed $\delta$ spectrum obtained
%after a cut $p_T^{rel} >1.2\; $GeV.
%The different contributions,
%shown in Figure~\ref{fig:high-purity-delta},
%are the absolute predictions from the $\delta$ fit
%for the limited $p_T^{rel}$ region.
%
%The observed impact parameter spectrum and the fit prediction,
%with a dominating beauty component, agree within the errors.
%
%Figure~\ref{fig:high-purity-ptrel} 
%shows the $p_T^{rel}$ spectrum after a
%cut on $\delta > 300\;\mu$m.
%
%The spectrum
%also agrees within the statistical
%errors with the fit prediction.
%
%The distributions of high $b$ purity 
%add to the confidence that the data are well understood.

Figure~\ref{fig:control-kin} shows the kinematic
distributions of the selected events as
obtained from data
together with the expectations of the RAPGAP Monte Carlo simulation
using the fractions of beauty, charm and light quarks obtained 
from the two-dimensional fit.
Figure~\ref{fig:control-1jet} 
shows the distributions of the 
muon transverse momentum \ptmu, the
pseudorapidity \etamu, the transverse momentum
$p_t^{*jet}$ of the highest-$p_t$
jet in the Breit frame and of the same jets in the 
lab-frame and the jet-multiplicity distributions.

The data are adequately described by the simulation.
The total systematic error is estimated to be 17\% with
contributions of similar size ($\sim 7\%$) 
due to track resolution uncertainties,
muon identification uncertainty 
and dependence on the
physics model. The latter is studied by
using for the modeling of beauty and charm events   
alternatively the CASCADE Monte Carlo simulation 
and by using either Peterson \cite{peterson} 
or Lund \cite{jetset} fragmentation.

%% \begin{table}[htb]
%% \begin{center}
%% \begin{tabular}{lr}
%% \hline
%% Track Reconstruction and CST Hit Linking Efficiency &  5\% \\
%% Muon Identification Efficiency &  7\% \\
%% Track Resolutions &  7\% \\
%% Jet Reconstruction &  7\% \\
%% Trigger & 5\% \\
%% Luminosity & 2\% \\
%% MC statistics & 5\% \\ 
%% Parton Evolution (RAPGAP / CASCADE) & 7\% \\
%% Fragmentation (Lund / Peterson) & 7\% \\
%% $K,\pi$-inflight decays ($\pm$ Factor 2) & 2\% \\
%% \hline
%% \hline
%% Total & $\sim$ 18\% \\
%% 
%% \end{tabular}
%% \end{center}
%% \caption{List of systematic uncertainties}
%% \label{tab:syserr}
%% \end{table}
%
%-------------------------------------------------------

\section{Results}
\label{sec:results}

The cross section measurements reported here are obtained from the
likelihood fit to the two-dimensional distribution of \ptrel and $\delta$.
%
The number of beauty events in the data, as estimated from the fit,
is translated into a cross section by dividing by the 
detector acceptance, the efficiency and the integrated luminosity.
%
The detector acceptances and efficiencies are determined 
from the RAPGAP Monte Carlo simulation.  
%

The jet-muon beauty production cross section, 
$\sigma_{vis}(ep \rightarrow e b\bar{b} X \rightarrow e j\mu X)$, is measured
in the visible range 
$2< Q^2 < 100$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, $-0.75<\eta^{\mu}<1.15$,
$p_t^{*jet} > 6$ GeV and $|\eta^{jet}|<2.5$. 
The muon must be associated with the jet.
The cross section is defined for jets which include 
all final state particles.
The visible cross section is measured as
$$
 \sigma_{vis}(ep \rightarrow e b\bar{b} 
 \rightarrow e j\mu X) = (8.8 \pm 1.0 (stat.) \pm 1.5 (sys.)) {\rm pb}.
$$

In comparison the prediction from the NLO QCD calculation 
including corrections for fragmentation and hadronisation 
is $(7.3^{+1.0}_{-1.5})$ pb.

The differential cross sections are measured
as function of the negative transverse momentum squared
of the exchanged photon
$Q^2$ (figures~\ref{fig:xsec-q2} and \ref{fig:xsec-q2-nlo}), the 
scaling variable $x$
(figures~\ref{fig:xsec-xbj} and \ref{fig:xsec-xbj-nlo}) and the transverse
momentum of the muon jet in the Breit frame, 
$p^*_{t,jet}$ (figures~\ref{fig:xsec-ptj} and \ref{fig:xsec-ptj-nlo}).
%
The cross section values are determined 
separately for each bin, using the beauty 
fraction from the fit to the 
two-dimensional distribution of \ptrel and \del
in that bin.
%
The cross section is obtained by dividing 
the number of beauty events from the fit 
by the detector acceptance and efficiency,
the integrated luminosity and the width of the bin.
%
%correcting 
%for detector efficiencies and acceptances.

The data are compared with expectations obtained from 
the RAPGAP and CASCADE generators and 
the prediction from the QCD NLO calculation. 
%
All generators, RAPGAP and CASCADE, give a good
description of the shapes of the distributions
observed in the data. The RAPGAP prediction is
too low in normalization. 
%
The NLO calculations show good agreement with the data.
%
\section{Conclusions}
\label{sec:conclusions}

A new measurement of beauty production cross sections 
performed with the H1 detector at HERA is presented.
%
The analysis uses semi-muonic decays of 
$b$-flavoured hadrons and exploits their lifetime and mass properties 
in a simultaneous fit to the 
impact parameter and relative transverse momentum distribution 
of the decay muons.
%
The total visible jet-muon cross section, defined in the region
$2< Q^2< 100$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, $-0.75<\eta^{\mu}<1.15$,
$p_t^{*jet} > 6$ GeV and $|\eta^{jet}|<2.5$, 
is measured to be $(8.8 \pm 1.0 (stat.) \pm 1.5 (sys.))$ pb.

The cross sections are also measured differentially 
in $Q^2$, $x$ and $p^*_{t,jet}$. Monte Carlo generators
show reasonable agreement with the shapes 
of the data. RAPGAP is lower than the data by about a factor of two.
The NLO calculations show good agreement with the data.
The prediction for the total visible jet-muon cross 
from the NLO QCD calculation including
fragmentation and hadronisation corrections as described in section 
\ref{sec:nlo} is $(7.3^{+1.0}_{-1.5}) {\rm pb}$.

%
%   References for Contact Interaction paper
%
\begin{thebibliography}{99}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\cite{Adloff:1999nr}
\bibitem{Adloff:1999nr}
C.~Adloff {\it et al.}  [H1 Collaboration],
%``Measurement of open beauty production at HERA,''
Phys.\ Lett.\ B {\bf 467} (1999) 156
[Erratum-ibid.\ B {\bf 518} (2001) 331] [hep-ex/9909029].
%%CITATION = HEP-EX 9909029;%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\cite{h1bprelim}
\bibitem{h1bprelim}
H1 Collaboration, Cont.~paper to the ICHEP 2000
conference, Osaka, Japan, July 2000.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\cite{Breitweg:2000nz}
\bibitem{Breitweg:2000nz}
J.~Breitweg {\it et al.}  [ZEUS Collaboration],
%``Measurement of open beauty production in photoproduction at HERA,''
Eur.\ Phys.\ J.\ C {\bf 18} (2001) 625
[hep-ex/0011081].
%%CITATION = HEP-EX 0011081;%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\bibitem{zeusbprelim}
%ZEUS Collaboration, Contributed papers to the ICHEP 2002
%conference, Amsterdam, Netherlands, July 2002.

\bibitem{hadronb}
% CDF, D0 open b
CDF Coll., F.~Abe {\it et al.},
Phys.\ Rev.\ Let. 71 (1993) 2396, Phys.\ Rev.\ D 53 (1996) 1051; \\
D0 Coll., S. Abachi {\it et al.},
Phys.\ Rev.\ Let 74 (1995) 3548, Phys.\ Let.\ B 370 (1996) 239.

\bibitem{ggb} 
% L3 gg->bb
M.~Acciarri {\it et al.}  [L3 Collaboration],
%``Measurements of the cross sections for open charm and beauty  production in gamma gamma collisions at s**(1/2) = 189-GeV - 202-GeV,''
Phys.\ Lett.\ B {\bf 503}, 10 (2001)
arXiv:hep-ex/0011070.
%%CITATION = HEP-EX 0011070;%%
%A. Cailling, (OPAL Coll.), Proc. of PHOTON 2000, AIP conf. proc., v.571,276(2000)
% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\cite{Chekanov:2003si}
\bibitem{Chekanov:2003si}
S.~Chekanov {\it et al.}  [ZEUS Collaboration],
%``Beauty photoproduction measured using decays into muons in dijet events in e
%p collisions at s**(1/2) = 318-GeV,''
arXiv:hep-ex/0312057.
%%CITATION = HEP-EX 0312057;%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{h1bprel2003}
A.Aktas {\it et al.} [H1 Collaboration], paper
%`` Measurement of Beauty production at HERA using semi-muonic decays'',
contributed to the International Europhysics Conference, 2003, Aachen.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{Abt:1997xv}
I.~Abt {\it et al.}  [H1 Collaboration],
%``The Tracking, calorimeter and muon detectors of the H1 experiment at HERA ,''
Nucl.\ Instrum.\ Meth.\ A {\bf 386} (1997) 310 and 348.
%CITATION = NUIMA,A386,348;%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{cst}
% CST paper
D.~Pitzl {\it et al.},
%``The H1 silicon vertex detector,''
Nucl.\ Instrum.\ Meth.\ A {\bf 454}, 334 (2000)
arXiv:hep-ex/0002044.
%%CITATION = HEP-EX 0002044;%%
%preprint ETHZ-IPP-PR-2000-01, hep-ex/0002044, 2000.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{Nicholls:1996di}
T.~Nicholls {\it et al.}  [H1 SPACAL Group Collaboration],
%``Performance of an electromagnetic lead / scintillating 
%fiber calorimeter for the H1 detector,''
Nucl.\ Instrum.\ Meth.\ A {\bf 374} (1996) 149.
%%CITATION = NUIMA,A374,149;%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{basslerbernardi}
U.\,Bassler, G.\,Bernardi, Nucl.Instrum.Meth.A361:197-208,1995
hep-ex/9412004

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{kt}
% incl kt
S.~Catani, Yu.~Dokshitzer, M.H.Seymour and B.R.~Webber,
Nucl.\ Phys.\  B 406 (1993) 187.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\cite{Jung:1993gf}
\bibitem{Jung:1993gf}
H.~Jung,
 %``Hard diffractive scattering in high-energy e p collisions and the Monte
%Carlo generation RAPGAP,''
Comput.\ Phys.\ Commun.\  {\bf 86} (1995) 147.
%%CITATION = CPHCB,86,147;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{cteq5l} 
L.~Lai {\it et al.} [hep-ph/9903282].
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\cite{Sjostrand:1993yb}
\bibitem{PYTHIA}
%\bibitem{Sjostrand:1993yb}
T.~Sjostrand,
%``High-energy physics event generation with PYTHIA 5.7 and JETSET 7.4,''
Comput.\ Phys.\ Commun.\  {\bf 82} (1994) 74.
%%CITATION = CPHCB,82,74;%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\bibitem{grvg}
%M.~Gl\"uck, E.~Reya and A.~Vogt, Phys. Rev.D45, 3986(1992); Phys. Rev. D46, 1973 (1992).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% CASCADE
%\cite{Jung:2000hk}
\bibitem{Jung:casc}
H.~Jung and G.~P.~Salam,
%``Hadronic final state predictions from CCFM: The hadron-level Monte  Carlo generator CASCADE,''
Eur.\ Phys.\ J.\ C {\bf 19} (2001) 351
[hep-ph/0012143];\\
%%CITATION = HEP-PH 0012143;%%
%\cite{Jung:2001hx}
%\bibitem{Jung:2001hx}
H.~Jung,
%``The CCFM Monte Carlo generator CASCADE,''
Comput.\ Phys.\ Commun.\  {\bf 143} (2002) 100
[hep-ph/0109102].
%\bibitem{Jung:2000hk}
%H.~Jung and G.~P.~Salam,
%``Hadronic final state predictions from CCFM: The hadron-level Monte  Carlo generator CASCADE,''
%Eur.\ Phys.\ J.\ C {\bf 19} (2001) 351
%[hep-ph/0012143].
%%CITATION = HEP-PH 0012143;%%
%\cite{Jung:2001hx}
%\bibitem{Jung:2001hx}
%H.~Jung,
%``The CCFM Monte Carlo generator CASCADE,''
%Comput.\ Phys.\ Commun.\  {\bf 143} (2002) 100
%[hep-ph/0109102].
%
%
%%CITATION = HEP-PH 0109102;%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% CCFM
%\cite{CCFM}
\bibitem{ccfm}
M.~Ciafaloni,
%``Coherence Effects In Initial Jets At Small Q**2 / S,''
Nucl.\ Phys.\ B {\bf 296} (1988) 49;   \\
%%CITATION = NUPHA,B296,49;%%
S.~Catani, F.~Fiorani and G.~Marchesini,\\
%``QCD Coherence In Initial State Radiation,''
Phys.\ Lett.\ B {\bf 234} (1990) 339,
%%CITATION = PHLTA,B234,339;%%
%\cite{Catani:1989sg}
%S.~Catani, F.~Fiorani and G.~Marchesini,
%``Small X Behavior Of Initial State Radiation In Perturbative QCD,''
Nucl.\ Phys.\ B {\bf 336} (1990) 18;\\
%%CITATION = NUPHA,B336,18;%%
G.~Marchesini,
%``QCD coherence in the structure function and associated distributions at small x,''
Nucl.\ Phys.\ B {\bf 445} (1995) 49.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{Harris:1995dv}
B.W.~Harris and J.~Smith, NUCL.\ PHYS.\ B\ {\bf 452} (1995) 109.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{peterson}
% Peterson
C.~Peterson, D.~Schlatter, I.~Schmitt, and P.M.~Zerwas, 
Phys.\,Rev.\ D 27 (1983) 105.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% \bibitem{mrs}
%% A.D.~Martin, R.G.~Roberts and W.J.~Stirling, Phys.Lett. B354, 155 (1995);
%% A.D.~Martin, R.G.~Roberts, W.J.~Stirling and R.S.~Thorne, Eur. Phys. J. C4 (1998) 463.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\bibitem{jetset}
T.~Sj\"ostrand,
%``High-energy physics event generation with PYTHIA 5.7 and JETSET 7.4,''
Comput.\ Phys.\ Commun.\  {\bf 82} (1994) 74.
%%CITATION = CPHCB,82,74;%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%\bibitem{AROMA}
%% AROMA
%G.~Ingelman, J.~Rathsman and G.A.~Schuler,
%Comput.\,Phys.\,Commun.\ 101 (1997) 135.
%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% \bibitem{Jung:2001rp}
%% H.~Jung,
%% %``Heavy quark production at the TEVATRON and HERA using k(t)  factorization with CCFM evolution,''
%% Phys.\ Rev.\ D {\bf 65} (2002) 034015 [hep-ph/0110034];\\
%% %\cite{Jung:2001ac}
%% %\bibitem{Jung:2001ac}
%% H.~Jung,
%% %``Unintegrated parton densities applied to heavy quark production in the  CCFM approach,''
%% J.\ Phys.\ G {\bf 28} (2002) 971
%% [hep-ph/0109146].
%% %%CITATION = HEP-PH 0109146;%%
%% %%CITATION = HEP-PH 0110034;%%H.~Jung, Phys.~Rev.~D {\bf 65} 034015 (2002). 
%% \bibitem{tankredi}
%% T.~Carli, V.~Chiochia, K.~Klimek [hep-ph/0305103]. 
%% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


\clearpage
\end{thebibliography}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig1.eps,width=15cm}}
\end{picture}
\caption{Distribution of the impact parameter \del of the muon track.
The data (points) are compared with the RAPGAP Monte Carlo
simulation (solid line). The decomposition
into the $b$ (dashed line), the $c$ (dotted line)
and the light quark (dash-dotted line) components
is determined from a fit to the two-dimensional  
distribution of \ptrel and \del (see text).}
\label{fig:signal-delta}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig2.eps,width=15cm}}
\end{picture}
\caption{Distribution of transverse muon momentum \ptrel relative
to the jet axis.
The data (points) are compared with the RAPGAP Monte Carlo
simulation (solid line). The decomposition
into the $b$ (dashed line), the $c$ (dotted line)
and the light quark (dash-dotted line) components
is determined from a fit to the two-dimensional  
distribution of \ptrel and \del (see text).}
\label{fig:signal-ptrel}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig3.eps,width=15cm}}
\end{picture}
\caption{Distribution of the impact parameter \del of muon tracks
with enhanced $b$-fraction by a cut on \ptrel $>1.2$ GeV
The data (points) are compared with the RAPGAP Monte Carlo
simulation (solid line). The $b$, $c$ and $uds$ fractions
are fixed from the same combined fit to \del and \ptrel
as for figures \ref{fig:signal-ptrel} and \ref{fig:signal-delta}.}
\label{fig:signal-highp-delta}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig4.eps,width=15cm}}
\end{picture}
\caption{Distribution of transverse muon momentum \ptrel relative
to the jet axis for events with an impact parameter $\delta > 0.01$ cm.
The data (points) are compared with the RAPGAP Monte Carlo
simulation (solid line). The $b$, $c$ and $uds$ fractions
are fixed from the same combined fit to \del and \ptrel
as for figures \ref{fig:signal-ptrel} and \ref{fig:signal-delta}.}
\label{fig:signal-highp-ptrel}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,20.)
\put(-1.3,0.){\epsfig{file=H1prelim-04-071.fig5.eps,width=18cm}}
\end{picture}
\caption{
Distribution of the scattered electron energy and polar angle,
the photon virtuality $Q^2$ and inelasticity $y$
as well as logarithm of the scaling variable $x$.
%
The data are compared to the RAPGAP Monte Carlo simulation.
%
The estimated contributions of beauty, charm and light
quark events, taken from the fit result, 
are shown as separate curves.}
\label{fig:control-kin}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,20.)
\put(-1.3,0.){\epsfig{file=H1prelim-04-071.fig6.eps,width=18cm}}
\end{picture}
\caption{
Distributions of the muon transverse momentum \ptmu, the
pseudorapidity \etamu, the transverse momentum
of the jet in the laboratory frame $p_t^{jet}$ and in the Breit frame
$p_t^{*jet}$ and the jet multiplicity.
%
The data are compared to the RAPGAP Monte Carlo simulation.
%
The estimated contributions of beauty, charm and light
quark events, taken from the fit result, 
are shown as separate curves.}
\label{fig:control-1jet}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig7.eps,width=16cm}}
\end{picture}
\caption{Differential dijet muon beauty production cross section 
$d\sigma/dQ^2(ep \rightarrow eb\bar{b}X \rightarrow ej\mu X)$ as a function
of $Q^2$ in 
the range $100>Q^2>2$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, 
$-0.75<\eta^{\mu}<1.15$, $p_t^{*jet} > 6$ GeV and $|\eta^{jet}|<2.5$.
The inner error bars show the statistical error, the outer error bars represent
the statistical and systematic uncertainty added in quadrature.
Also shown are the predictions from the Monte Carlo generator 
programs RAPGAP (solid line) and 
CASCADE (dashed line).}
\label{fig:xsec-q2}
\end{figure} 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig8.eps,width=16cm}}
\end{picture}
\caption{Differential dijet muon beauty production cross section 
$d\sigma/dQ^2(ep \rightarrow eb\bar{b}X \rightarrow ej\mu X)$ as a function
of $Q^2$ in 
the range $100>Q^2>2$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, 
$-0.75<\eta^{\mu}<1.15$, $p_t^{*jet} > 6$ GeV and $|\eta^{jet}|<2.5$.
The inner error bars show the statistical error, the outer error bars represent
the statistical and systematic uncertainty added in quadrature.
Also shown is the prediction from a pQCD NLO calculation \cite{Harris:1995dv}
at parton level (dashed line) and hadron level (solid line).
The band shows the uncertainty obtained from
variations of the $b$-quark mass, $\mu_r$ and $\mu_f$ (see text).}
\label{fig:xsec-q2-nlo}
\end{figure} 
\newpage

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig9.eps,width=16cm}}
\end{picture}
\caption{Differential dijet muon beauty production cross section 
$d\sigma/d\log x(ep \rightarrow eb\bar{b}X \rightarrow ej\mu X)$ 
as a function of $x$ in 
the range $100>Q^2>2$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, 
$-0.75<\eta^{\mu}<1.15$,
$p_t^{*jet} > 6$ GeV and $|\eta^{jet}|<2.5$.
The inner error bars show the statistical error, the outer error bars comprise
the statistical and systematic uncertainty added in quadrature.
Also shown are the predictions from the Monte Carlo 
generator programs RAPGAP (solid line) 
and CASCADE (dashed line).}
\label{fig:xsec-xbj}
\end{figure} 
\newpage

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig10.eps,width=16cm}}
\end{picture}
\caption{Differential dijet muon beauty production cross section 
$d\sigma/d\log x(ep \rightarrow eb\bar{b}X \rightarrow ej\mu X)$ 
as a function of $x$ in 
the range $100>Q^2>2$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, 
$-0.75<\eta^{\mu}<1.15$,
$p_t^{*jet} > 6$ GeV and $|\eta^{jet}|<2.5$.
The inner error bars show the statistical error, the outer error bars comprise
the statistical and systematic uncertainty added in quadrature.
Also shown is the prediction from a pQCD NLO calculation \cite{Harris:1995dv}
at parton level (dashed line) and hadron level (solid line).
The band shows the uncertainty obtained from
variations of the $b$-quark mass, $\mu_r$ and $\mu_f$ (see text).}
\label{fig:xsec-xbj-nlo}
\end{figure} 

\newpage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig11.eps,width=16cm}}
\end{picture}
\caption{Differential dijet muon beauty production cross section 
$d\sigma/dp^*_{t,jet}(ep \rightarrow eb\bar{b}X \rightarrow ej\mu X)$ 
as a function of $p^*_{t,jet}$ in the Breit frame, 
in the range $100>Q^2>2$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, 
$-0.75<\eta^{\mu}<1.15$ and $|\eta^{jet}|<2.5$.
The inner error bars show the statistical error, the outer error bars comprise
the statistical and systematic uncertainty added in quadrature.
Also shown are the predictions from the Monte Carlo 
generator programs RAPGAP (solid line) 
and CASCADE (dashed line).}
\label{fig:xsec-ptj}
\end{figure} 
\newpage

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[t]
\setlength{\unitlength}{1cm} 
\begin{picture}(14.0,15.)
\put(0.,0.){\epsfig{file=H1prelim-04-071.fig12.eps,width=16cm}}
\end{picture}
\caption{Differential dijet muon beauty production cross section 
$d\sigma/dp^*_{t,jet}(ep \rightarrow eb\bar{b}X \rightarrow ej\mu X)$ 
as a function of $p^*_{t,jet}$ in the Breit frame, 
in the range $100>Q^2>2$ GeV$^2$, $0.1<y<0.7$, \ptmu $>2.5$ GeV, 
$-0.75<\eta^{\mu}<1.15$ and $|\eta^{jet}|<2.5$.
The inner error bars show the statistical error, the outer error bars comprise
the statistical and systematic uncertainty added in quadrature.
Also shown is the prediction from a pQCD NLO calculation \cite{Harris:1995dv}
at parton level (dashed line) and hadron level (solid line).
The band shows the uncertainty obtained from
variations of the $b$-quark mass, $\mu_r$ and $\mu_f$ (see text).}
\label{fig:xsec-ptj-nlo}
\end{figure} 


\end{document}

