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\newcommand{\GeV}{\rm GeV}
\newcommand{\TeV}{\rm TeV}
\newcommand{\pb}{\rm pb}
\newcommand{\cm}{\rm cm}
\newcommand{\hdick}{\noalign{\hrule height1.4pt}}
\newcommand{\ra}{\rightarrow}
\newcommand{\ccb}{c\bar{c}}
\newcommand{\bbb}{b\bar{b}}
\newcommand{\ptrel}{$p_t^{rel}\,$}
\newcommand{\ptr}{$p_t\,\,$}
\newcommand{\del}{$\delta\;$}
\newcommand{\ptmu}{$p_t^{\mu}$}
\newcommand{\etamu}{$\eta^{\mu}$}
\newcommand{\ptjet}{$p_t^{jet}$}
\newcommand{\etjet}{$E_t^{jet}$}
\newcommand{\etajet}{$\eta^{jet}$}
\newcommand{\xgobs}{$x_{\gamma}^{obs}\,$}
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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
                 XXII International Symposium on Lepton-Photon Interactions at High Energy, 
		 June 30, 2005, Uppsala}} \\
                 & Abstract:        & {\bf 409}    &\\
                 & Parallel Session & {\bf Flavor physics}   &\\ \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 
    Study of Jet Shapes in Charm Photoproduction at HERA
   }

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

\begin{abstract}

\noindent
% 
Charm dijet events 
are investigated in the photoproduction kinematic range
in $ep$ collisions at HERA. 
%
One jet is tagged by a muon
as being initiated by a charm quark.
%
The shape of the other jet is studied 
in order to distinguish if it is initiated by a quark or a gluon in order to
shed light on the production mechanism of charm
events in $ep$ collisions.
%
%
The data were collected with the H1 Experiment 
in the years 1999-2000.
%
The jet shapes are studied as function of kinematic variables
such as the transverse momentum, energy and pseudorapidity of the
jet and the quantity $x_\gamma^{obs}$. 
%
The shapes are found to be well described by the leading order 
plus parton shower Monte Carlo
simulation PYTHIA in 
the region of 
large $x_\gamma^{obs}>0.75$, where according to the simulation
the jets are dominantly charm quark initiated. 
%
Deviations are
observed 
for small  $x_\gamma^{obs}<0.75$, where resolved photon 
events are expected to contribute significantly and
more gluon jets are expected.
%
No such deviations are observed in a dijet photoproduction
sample without muon requirements, 
which is dominated by light quark production.
\end{abstract}

\end{titlepage}

\pagestyle{plain}

\section{Introduction}

Charm production in $ep$ collisions at HERA  
is dominated by photon gluon fusion
processes (fig.~\ref{fig:feynman}).\/
%
In photoproduction the exchanged photon is quasi-real
and in addition to direct photon processes (fig.~\ref{fig:feynman}a),\/ 
resolved photon processes  (fig.~\ref{fig:feynman}b-d)
can contribute significantly, where the photon acts as a source of quarks and
gluons which participate in the hard interaction. 
%
A key question is to which extent the charm production
can be attributed to
the so called c-excitation processes (fig.~\ref{fig:feynman}c-d),
where the c quark is a constituent of the resolved photon.
%
In perturbative QCD at leading order only the c-excitation
processes produce a hard gluon in addition
to a hard charm quark, while
the direct photon (fig.~\ref{fig:feynman}a)
and other hadron-like resolved processes (fig.~\ref{fig:feynman}b)
lead to the production of a  $c\bar{c}$ pair.


The aim of the present study is the distinction of the charm quark-pair component
from the charm quark-gluon events. 
In this analysis dijet events in which one jet is tagged as being initiated by the charm quark
are used to study the shapes of the other jet.
Quark and gluon initiated jets are expected to have 
different `shapes', i.e. a different distribution of the 
energy flow as a function of the radial distance from the jet axis.
Such differences have been observed previously between jets initiated by light
quarks and by gluons ~\cite{opal}, while 
$b$ quark initiated jets were found to have almost the same shape as gluon jets. 
%
\section{Experimental Method}
The jet shapes are studied using the variable: 
\begin{equation}
\psi(r)  =
\frac{p_t^{jet}(r)}{p_{t}^{jet}(r=R)}.
\end{equation}
%
$\psi(r)$, `the integrated jet shape', is the fraction of the jet transverse  momentum deposited
within a cone of the radius $r$ around the jet axis relative to the total
transverse momentum of the jet within $R$ (figure~\ref{fig:jetcone}).      
Transverse momenta are measured with respect to the beam axis. 
The radius is defined as $r=\sqrt{\Delta \eta^2 + \Delta \phi^{2}}$, 
where $\Delta \eta$ and $\Delta \phi$ are the distances of the individual 
particles forming the jet  
to the jet axis in pseudorapidity\footnote{The pseudorapidity 
$\eta$ of an object with polar angle $\theta$ is given by
$\eta = -\ln \; \tan (\theta/2)$, where $\theta$ is
measured with respect to the $z$-axis given by the proton beam direction.}
$\eta$ and azimuthal angle $\phi$, respectively. 
The variable \psir is averaged over the 
jets of the selected event sample 
$$\langle\psi(r)\rangle=\frac{1}{N_{jets}}\sum_{jets}\psi(r).$$
%

The integrated jet shape is studied as a function of $r$ at a given value of 
$R$ (we choose $R=1$ for the analysis, since the same value is chosen
in the jet algorithm). 
Due to differences in the formation processes (fig.~\ref{fig:branching}) 
of charm and gluon jets the latter are expected to be broader and contain more particles~\cite{ellis}. Hence the
distribution of \psir is expected to be different. For gluons
the full transverse momentum is reached more slowly and at a given radius the value is on
average smaller.
%
Fig.~\ref{fig:psiopal} shows the differences in the \psir distributions
of light quark and gluon jets as observed for high jet energies
in $e^+e^-$ collisions at LEP~\cite{opal}. 
%
The jet energies in the present analysis are lower but still high enough to 
expect significant differences in the jet shapes of gluon and 
charm initiated jets, according to the Monte Carlo Simulation (e.g. using the
PYTHIA~\cite{PYTHIA} generator).
%
\section{Event Selection}
%
The H1 detector is described in detail in \cite{Abt:1997xv}, 
a discussion of the components most relevant for this
analysis can be found in~\cite{Aktas:2005zc}.

\subsection*{Preselection of the Dijet Sample with a High \ptr\ Muon}
%
The analysis is based on the event sample selected for the recent determination of
the beauty cross section~\cite{Aktas:2005zc}. 
%
The data were recorded
in 1999 and 2000 and correspond
to an integrated luminosity of $48\,$pb$^{-1}$.
%
In~\cite{Aktas:2005zc} a detailed account of the event selection
is given, e.g. of the triggering of events, of the selection of 
photoproduction and of many other aspects.
%/
The accepted range of negative four-momentum
transfer squared $Q^2\,$ is restricted to $Q^2<1$ GeV$^2$ and
the inelasticity $y$ to \mbox{0.2 $<y<$ 0.8}. 
%
%
Jets are reconstructed
using the inclusive $k_t$ algorithm~\cite{Ellis:1993tq,Catani:1993hr}
in the $p_t$ recombination scheme (see~\cite{Butterworth:2002xg}),
giving massless jets.
%
The algorithm, with a distance parameter in the $\eta$-$\phi$ plane of $R=1$,
is applied to all hadronic final state particles
using a combination
of tracks and calorimeter energy deposits.
% 
The selection requires at least two jets with 
transverse energy $p_t^{jet_{1(2)}}>7(6)$ GeV,
of which at least one contains a muon candidate.
% 
Muons are selected in the 
angular range $35^{\circ} < \theta (\mu)<130^{\circ}$,
and are required to have transverse momenta $p_t^{\mu}>2.5$ GeV.
%
Only muon tracks are selected for which 
associated hits are found in both layers 
of the H1 vertex detector~\cite{cst}, thus providing 
high spatial track resolution close to the
ep collision vertex.
%
The selection cuts for the Dijet + Muon sample are summarized in 
table~\ref{tab:cuts}.
%

For the measurement of 
the beauty cross section~\cite{Aktas:2005zc},  two observables were used
to separate beauty events from charm events and light quark background, exploiting
the large mass and the long lifetime of the b-quark, respectively. These quantities are
used here to define a charm  enriched sample and to check the  
fraction of charm events in the final selection.
\begin{enumerate}
\item
The relative transverse momentum $p_t^{rel}$ of the muon with respect to the axis of the associated jet.
\item
The impact parameter $\delta$ of the muon, 
which is the distance of the track in the transverse plane with respect to the ep collision vertex.
\end{enumerate}

The distributions of \ptrel and $\delta$ 
for the selected dijet plus muon event sample
are shown in fig.~\ref{fig:ptreldelta}. 
%
The fractions of charm, beauty and uds events 
in the data are 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 PYTHIA Monte
Carlo simulation.  
%
The relative weights of all three components are adjusted 
such that the likelihood is maximized.
%
The overall normalization of the summed contributions
is adjusted to match the data.
%
The result of this fit is also illustrated in
fig.~\ref{fig:ptreldelta}.
%
Both the \ptrel and $\delta$ data distributions
are nicely described by the sum of the three contributions,
which are also shown separately.
%
\subsection*{Selection of a Charm Enriched Sample}
In order to enrich events containing charm quark decays a cut on the
transverse momentum 
\ptrel of the muon track  
relative to the momentum of the associated jet, \ptrel$<1\,\GeV$, is
imposed. The final sample then contains 800 events. The combined fit of \ptrel
and $\delta$ leads to a charm fraction of $73\pm3\%$ in this region compared to
$71\pm2\%$ expected from the PYTHIA Monte Carlo simulation. 
%
The remaining background due to $b$ and light quark (`uds') production is 
subtracted statistically, using the fractions as predicted in the 
PYTHIA Monte Carlo simulation. 
Note that this procedure of selecting a charm enriched sample is independent of the production mechanism but only depends on the decay and fragmentation properties of the charm hadrons. 
% 
\subsection*{Selection of a Dijet Sample}
For comparison a dijet event sample is selected 
which fulfills the same jet selection criteria as 
the charm sample except for the requirement of a high \ptr\ muon.
%
Photoproduction is
ensured by the presence of the scattered beam lepton in the low angle
tagging device which selects $Q^2<0.01\,\GeV^2$ and also serves for triggering.
%
The inelasticity $y\,$ is restricted to the range \mbox{0.3 $<y<$ 0.65}. 
%
The event selection cuts 
are summarized in table~\ref{tab:cuts}.
%
This event sample is dominated by the production of light quarks ($\sim75\%$). 
%
\section{Monte Carlo Simulations}
\label{sec:mc}
%
Monte Carlo event samples for the processes 
 $ep\ra e\ccb X$, $ep\ra e\bbb X$ and light quark production
are generated using the PYTHIA program~\cite{PYTHIA}
which is based on leading order QCD and parton showers.  
%
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. The Peterson
fragmentation function~\cite{peterson} is used for the hadronisation 
of the heavy quarks.
%
The CTEQ5L~\cite{cteq5l} parton densities are used
for the proton and those of GRVG-LO~\cite{grvg} for the photon. 
%
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 program CASCADE \cite{Jung:casc}, a Monte Carlo generator which
implements the CCFM parton evolution equation
\cite{ccfm},
uses unintegrated parton densities JS2001 and of-shell matrix elements 
is used for a cross check. 
For comparison with the dijet sample an inclusive PYTHIA data set is used.
The generated events after fragmentation are passed through a detailed 
simulation of the H1 detector and the same reconstruction software is used as 
for the data.

\section{Results}

In figures~\ref{fig:charmcontrol} and \ref{fig:dijetcontrol} distributions 
are shown for the charm enriched and the dijet samples.
where the data are compared to the PYTHIA Monte Carlo simulations.
%
The overall normalization of PYTHIA in the charm enriched sample is 
adjusted to match the data, while the relative fractions of charm, beauty 
and light quark events as predicted by PYTHIA.
The fraction \xgobs of the photon energy entering
the hard interaction is estimated using the 
observable
$$
\xgobsm = \frac{ \sum_{Jet_1}(E-p_z) + 
                 \sum_{Jet_2}(E-p_z)}{\sum_{h}(E-p_z)},
$$
where the sums in the numerator run over
the particles associated with the two jets
and that in the denominator over all 
detected hadronic final state particles.
For the direct process (figure~\ref{fig:feynman}a),
$\xgobsm$ approaches unity, since the hadronic final state consists of
only the two hard jets and the proton remnant in the
forward region, which however contributes little to $\sum_{h}(E-p_z)$.
%
In resolved processes $\xgobsm$ can be small.


\label{sec:results}
%
The distributions of the averaged integrated jet shapes \psia 
as functions of the cone radius $r$ are shown in 
figures~\ref{fig:psidijet} and \ref{fig:psicharm}\ for the 
light quark dominated dijet sample and 
for the charm sample, respectively.
%
The distributions are presented for two separate regions of
the variable $x_{\gamma}^{obs}$.
%
For the dijet sample both selected jets enter the distributions.
%
In the charm sample the jet tagged by the muon is initiated by a charm quark in 95\% of the events
according to the PYTHIA Monte Carlo simulation.
%
The other jet is studied and enters the jet shape distributions.
%
The background in this sample from beauty and light quark events is subtracted
from the \psir distribution before calculating the average $\langle\psi(r)\rangle$ (see figure \ref{fig:psi}).
%
In figures~\ref{fig:psidijet} and \ref{fig:psicharm} 
the PYTHIA predictions are shown with the data.
%
In addition to the total  prediction the curves
for the direct and resolved photon events 
are shown separately.
%
For the dijet sample
good agreement between data and
PYTHIA prediction can be observed both at low and high $x_{\gamma}^{obs}$.
%
For charm the data are described well by the PYTHIA prediction at high
\xgobs but disagreement is observed in the region of $\xgobsm\leq0.75$. 
In this region the
data show approximately the same shape as in the region  $\xgobsm>0.75$.
%
The PYTHIA simulation however predicts a slower rise of \psia
due to the presence of gluon jets in the resolved photon sample.
The charm data are shown again in figure~\ref{fig:psicharmcasc} with the prediction of 
the CASCADE model, where no explicit resolved component is generated. 
The CASCADE prediction  describes the data perfectly in the high \xgobs region and is 
closer to the data in the low \xgobs region than PYTHIA.
%
In figures~\ref{fig:dijetpsi05} and \ref{fig:charmpsi05}
the averaged integrated jet shapes at $r/R=0.5$ are shown for the dijet and 
the charm samples as a functions of 
the pseudorapidity of the jet, its transverse momentum, energy and $\xgobsm$.
%
PYTHIA describes the dijet data well everywhere. 
%
For the charm data the
distribution as a function of pseudorapidity and \ptjet\ is well 
described, however deviations are seen at high jet energy and low $\xgobsm$.


In figure~\ref{fig:charmth} the charm data are shown again with the predictions
from the PYTHIA and CASCADE models. 
CASCADE is somewhat closer to the data at low $\xgobsm$, but at high jet energy CASCADE predicts the same value as PYTHIA. 

In figure~\ref{fig:charmth} a result from PYTHIA omitting the simulation of 
interactions between the photon and proton remnants (`multiple interactions')
is also shown. This has a small effects on the 
jet shapes: the simulation without multiple interactions is closer to the 
data at low $\xgobsm$, while the 
description at high \xgobs remains good.
%
Various systematic checks have been carried out for the charm sample.
%
Variation of the background due to $b$ quarks and light quarks
or of the Peterson fragmentation parameter $\epsilon$ between 0.03 and 0.08 (default value 0.058) did not change the distributions.
A direct comparison of the jet shapes in charm and dijet data 
is shown in figures~\ref{fig:charmdijet} and \ref{fig:dijchdep}.
%
A clear difference between the data is seen at low values of $\xgobsm$ between the shapes of 
charm and dijet events as function of $r/R$. In figure~\ref{fig:dijchdep} the dependence of \psia at $r/R=0.5$ is compared.
The difference between dijet and charm events is seen at large values of the pseudorapidity, i.e. in the forward direction, large jet energies and low $\xgobsm$.

%
\section{Conclusions}
\label{sec:conclusions}

Jet shapes are studied in a charm dijet photoproduction
sample with the H1 detector at HERA. With the final selection cuts, 
about 71\% of the sample is due to charm events (according to the 
simulation), the rest is due to 
beauty and light quark background with about equal shares. The background 
is subtracted statistically to obtain a pure charm sample.
%
The charm events are tagged by a high \ptr muon which is associated
to one of the jets and thus identifies this jet as being charm
quark initiated.
%
The jet not containing the muon is studied and compared to
predictions by a PYTHIA Monte Carlo simulation which contains direct and
resolved photon events.
%
The resolved component in PYTHIA is dominated by charm
excitation, where in addition to the charm quark jet (tagged by the muon) 
a gluon initiated jet is expected, which has a different shape than 
the charm jet.
%
In the charm data sample the jet shapes are however found to be similar in
direct and resolved photon enriched samples, 
while PYTHIA predicts significant differences due
to the different mixture of charm quark and gluon jets in direct
and resolved photon events.
%
For comparison a dijet sample was selected without the high \ptr muon, which
is expected to be dominated by light quark production.
%
Here the jet shapes are significantly different in direct and resolved photon
enriched data samples and in agreement with PYTHIA,
which predicts a large fraction of gluon jets in the resolved photon
sample.
%
We conclude that the discrepancy between the charm data and PYTHIA 
observed for the jet shapes in the resolved photon region 
%is not an artefact of the analysis but 
 indicates a lack of understanding of the charm production process in the resolved photon region.
%
\section*{Acknowledgements}
We are grateful to the HERA machine group whose outstanding efforts have
made this experiment possible. We thank the engineers and technicians
for their work in constructing and maintaining the H1 detector, our funding agencies
for financial support, the DESY technical staff for continual assistance and
the DESY directorate for support and for the hospitality which they
extend to the non  DESY members of the collaboration.

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\end{thebibliography}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\vspace{1cm}

\begin{table}[h]
\begin{center}
\begin{tabular}{|l|c|c|}
\hline & 
Dijet+Muon & Dijet \\
 \hline
$Q^2$ [GeV$^2$] & $< 1$ &  $<0.01$ \\ 
$y$  & 0.2~...~0.8 & 0.3~...~0.65 \\
\hline
$\#$ jets           & \multicolumn{2}{|c|}{$\ge 2$}\\
$p_t^{jet}$ [GeV]      &  \multicolumn{2}{|c|}{$>7(6)$ }\\

$|\eta_{lab}^{jet}|$    & $<1.7$ & $<1.7$ \\
\hline
$p_t^{\mu}$ [GeV]    & $>2.5$ & -- \\
Trigger & Muon and jets & E-Tagger\\
\hline
\end{tabular}
\caption{Selection cuts for the photoproduction dijet+muon and dijet data 
samples.}
\label{tab:cuts}
\end{center}
\end{table}

\begin{figure}[p]
\begin{center}
\epsfig{file=figs/d05-004f1.eps,width=12.3cm}
\epsfig{file=figs/hpp5.eps,width=2.8cm}
\end{center}
\centerline{a) \hspace{2.8cm} b)\hspace{2.8cm} c) \hspace{2.8cm} d) \hspace{2.8cm} e)}
%\put(0.8,4.5){Direct-$\gamma$}
%\put(4.7,4.5){Resolved-$\gamma$}
%\put(0.3,0.){a) $\gamma g$-Fusion}
%\put(3.6,0.){b) Hadron-like}
%\put(8.5,0.){c) $c$-Excitation}
\caption{Charm quark production processes in leading order pQCD.}
\label{fig:feynman}
\end{figure} 


\begin{figure}[p]
\begin{center}
\epsfig{file=figs/cone.epsi,height=6cm}
\end{center}
\caption{Definition of jet cones.}
\label{fig:jetcone}
\end{figure} 

\begin{figure}[p]
\begin{flushleft}
\epsfig{figure=./figs/splitting.epsi,height=3.3cm}
\end{flushleft}
\caption{Branching processes of quarks and gluons.}
\label{fig:branching}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/zpc186.f15.epsi,height=9cm}
\end{center}
\caption{\psia Spectra for light quark and gluons jets as measured by OPAL~\cite{opal}.}
\label{fig:psiopal}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/anal_talk2.OK.eps,angle=-90,width=16cm}
\end{center}
\caption{Determination of the charm fraction. The distributions of 
the relative momentum $p_t^{rel}$  of the muon w.r.t the jet-axis 
and the impact parameter $\delta$ of the muon track w.r.t the event vertex 
are shown. The solid line shows the expectation from the Monte Carlo simulation.
The light (dark) shaded histograms indicate the contributions from light quark (beauty)
events obtained from a fit to the data.}
\label{fig:ptreldelta}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/control_charmA.eps,angle=-90,width=15cm} \\
\vspace{0.7cm}
\epsfig{figure=./figs/control_charmB.eps,angle=-90,width=15cm} \\
\vspace{0.7cm}
\epsfig{figure=./figs/control_charmC.eps,angle=-90,width=15cm}
\end{center}
\caption{Control distributions for the charm enriched dijet plus muon sample. 
The data (points) are compared with the
PYTHIA Monte Carlo simulation (lines). The remaining background from $b$ quark and light quarks with fake muons (`uds') is shown separately. for the 
muon polar angle $\theta_{\mu}$ and transverse momentum $p_t^{\mu}$, 
the transverse momentum $p_t^{\mu-jet}$ of the jet associated to the muon,
the polar angle $\theta^{other~jet}$ and transverse momentum $p_t^{other~jet}$ of the
jet not associated to the muon, the number of jets with \ptjet$>2.5\,\GeV$, the photon proton
centre-of-mass-energy
$W_{\gamma p}$, the quantity $x_\gamma^{obs}$ and the 
hadronic energy flow, i.e. the hadronic particles as a function of the azimuthal
angle difference $\Delta \Phi$ with respect to the axis of the `other' jet.} 
\label{fig:charmcontrol}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/control_dijetsA.eps,angle=-90,width=15cm} \\
\vspace{0.7cm}
\epsfig{figure=./figs/control_dijetsB.eps,angle=-90,width=15cm}
\end{center}
\caption{Control distributions for the dijet sample. 
The data (points) are compared with the
PYTHIA Monte Carlo simulation (lines) for the 
polar angle $\theta^{jet}$ and transverse momentum $p_t^{jet}$
of the selected jets, the number of jets with \ptjet$>2.5\,\GeV$, 
the photon proton centre-of-mass-energy
$W_{\gamma p}$, the quantity $x_\gamma^{obs}$ and 
the hadronic energy flow, i.e. the hadronic particles as a function of the azimuthal
angle difference $\Delta \Phi$ with respect to the jet axis.} 
\label{fig:dijetcontrol}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./JetShapes/psi_charm.eps,height=8cm,angle=-90}
\end{center}
\caption{Distribution of \psir for a cone radius of $r/R=0.5$ before background subtraction compared with the PYTHIA simualtion. The shaded area represents the background due to b initated jets and the dotted area due to light quark jets.}
\label{fig:psi}
\end{figure} 
%
\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/jetshape_dijet_pyth_xg1.eps,angle=-90,width=6.5cm}
\hspace{1cm}
\epsfig{figure=./figs/jetshape_dijet_pyth_xg2.eps,angle=-90,width=6.5cm}
\end{center}
\vspace*{0.5cm}
\caption{\psia for the dijet event sample for two different regions of 
$x_{\gamma}^{obs}$. The data are compared to the prediction from PYTHIA.
The expected curves for direct photon (dashed)
and resolved photon (dotted) events from PYTHIA
are shown separately.}
\label{fig:psidijet}
%
\begin{center}
\epsfig{figure=./figs/jetshape_charm_pyth_xg1.eps,angle=-90,width=6.5cm}
\hspace{1cm}
\epsfig{figure=./figs/jetshape_charm_pyth_xg2.eps,angle=-90,width=6.5cm}
\end{center}
\vspace*{0.5cm}
\caption{\psia for the charm event sample for two different regions of 
$x_{\gamma}^{obs}$. The data are compared to the prediction from PYTHIA.
The expected curves for direct photon (dashed)
and resolved photon (dotted) events from PYTHIA
are shown separately.}
\label{fig:psicharm}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/jetshape_charm_casc_xg1.eps,angle=-90,width=6.5cm}
\hspace{1cm}
\epsfig{figure=./figs/jetshape_charm_casc_xg2.eps,angle=-90,width=6.5cm}
\end{center}
\vspace*{0.5cm}
\caption{\psia for the charm event sample for two different regions of 
$x_{\gamma}^{obs}$. The data are compared to the CASCADE prediction.}
\label{fig:psicharmcasc}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/dependence_dijet_pyth.eps,angle=-90,width=17cm}
\end{center}
\vspace*{1.5cm}
\caption{Differential distributions of $\langle\psi(r/R=0.5)\rangle$ as
  functions $\eta_{jet}$, $p_t^{jet}$, $E_{jet}$ and $x_{\gamma}^{obs}$
for the dijet event sample.
The predictions from the PYTHIA simulation are compared with the data.
%
The expected curves for direct photon (dashed)
and resolved photon (dotted) events from PYTHIA
are shown separately.}
\label{fig:dijetpsi05}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/dependence_charm_pyth.eps,angle=-90,width=17.cm}
\end{center}
\vspace*{1.5cm}
\caption{Differential distributions of $\langle\psi(r/R=0.5)\rangle$ as
  functions of $\eta_{jet}$, 
$p_t^{jet}$, $E_{jet}$ and $x_{\gamma}^{obs}$
for the charm event sample.
The predictions from PYTHIA are compared with the data.
The expectations for direct photon (dashed)
and resolved photon (dotted) events from PYTHIA
are shown separately.
 Also shown is the expectation for charm quarks from
 the CASCADE simulation (dash-dotted line).}
\label{fig:charmpsi05}
\end{figure} 

\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/dependence_charm_models.eps,angle=-90,width=17.cm}
\end{center}
\vspace*{1.5cm}
\caption{Differential distributions of $\langle\psi(r/R=0.5)\rangle$ as
  functions of $\eta_{jet}$, 
$p_t^{jet}$, $E_{jet}$ and $x_{\gamma}^{obs}$
for the charm event sample.
The predictions from PYTHIA with and without multiple interactions and CASCADE
  are compared with the data.}
\label{fig:charmth}
\end{figure}


\begin{figure}[p]
\begin{center}
\epsfig{figure=./figs/jetshape_dijet_charm_xg1.eps,angle=-90,width=6.5cm}
\hspace{1cm}
\epsfig{figure=./figs/jetshape_dijet_charm_xg2.eps,angle=-90,width=6.5cm}
\end{center}
%\vspace*{-1.cm}
\caption{\psia for the charm and dijet data samples in two different regions 
of $x_{\gamma}^{obs}$.}
\label{fig:charmdijet}
%
\begin{center}
\epsfig{figure=./figs/dependence_dijet_charm.eps,angle=-90,width=16.cm}
\end{center}
\vspace*{-0.5cm}
\caption{Differential distributions of $\langle\psi(r/R=0.5)\rangle$ as
  functions of $\eta_{jet}$, 
$p_t^{jet}$, $E_{jet}$ and $x_{\gamma}^{obs}$
for the charm and dijet event samples.
The predictions from PYTHIA for charm and dijets are shown with the data.}
\label{fig:dijchdep}
\end{figure} 

\end{document}