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\noindent
\begin{center}
%{\it {\large version of \today}} \\[.3em] 
\begin{small}
\begin{tabular}{llrr}
%Submitted to & \multicolumn{3}{r}{\footnotesize Electronic Access: {\it http://www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline 
%Submitted to & \multicolumn{3}{r}{\footnotesize {\it www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline 
Submitted to & & &
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,width=2.cm} \\[.2em] \hline
                & & & \\
\multicolumn{4}{l}{{\bf
                International Europhysics Conference 
                on High Energy Physics, EPS03},
                July~17-23,~2003,~Aachen} \\
                (Abstract {\bf 093} & Parallel Session & {\bf 4}) & \\
                & & & \\
\multicolumn{4}{l}{{\bf
                XXI International Symposium on  
                Lepton and Photon Interactions, LP03},
                August~11-16,~2003,~Fermilab} \\ 
                & & & \\
                \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 Inclusive Prompt Photon Production and with associated Jets 
Measurement of Prompt Photon Production    \\
 in \boldmath $\gamma p$ Interactions 
  }

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

\begin{abstract}

\noindent
    Results are presented on the photoproduction of
isolated prompt photons,
    both, inclusively and  
    associated with jets in the $\gamma p$ center of mass energy range
 $142 < W < 266$~GeV.
  The cross sections are given for the transverse momentum and
 pseudorapidity ranges of the
   photons 
    $5 < E_T^{\gamma} < 10$~GeV, $-1 < \eta^{\gamma} < 0.9$ and for the 
    associated jets in the range  
   $E_T^{jet} > 4.5$ GeV, $-1 < \eta^{jet} < 2.3$
    as a function of
    $E_T^{\gamma}, \eta^{\gamma}, E_T^{jet}, \eta^{jet}, x_p$ and
    $x_{\gamma}$, where  $x_{p}$ and $x_{\gamma}$ 
% $x_{\gamma}=(E_T^{jet}e^{-\eta^{jet}}+ E_T^{\gamma}e^{-\eta^{\gamma}})/2yE_e$
% and  $x^{p} = (E_T^{jet}e^{\eta^{jet}}+ E_T^{\gamma}e^{\eta^{\gamma}})/2E_p$
  correspond to
  the energy fractions of the incident proton and 
 exchanged photon, respectively, participating in the hard process. 
%    The photon has to be isolated.
% The transverse energy
%    in a cone in ($\eta,\phi$) of radius~1
%    around the photon $E_T^{cone}$ is required not to exceed
%    $0.1 \cdot E_T^{\gamma}$.
    The results are reasonably well described by pQCD calculations
in next to leading order.
%    by M. Fontannaz, J.P. Guillet and G. Heinrich,
%  Eur. Phys. J. C21 (2001) 303. 
%
%    This analysis is an extension of an inclusive prompt photon analysis
%    presented at ICHEP2002
%    (http://www-h1.desy.de/h1/www/publications/htmlsplit/H1prelim-02-152.long.html).
     The data were taken at HERA in the years 1996-2000
    corresponding to an integrated luminosity of 105 pb$^{-1}$.

\end{abstract}


\end{titlepage}

\pagestyle{plain}

\section{Introduction}

   High energy $ep$ collisions at HERA
  proceed mainly through electron\footnote{The term
  ``electron'' is used for electrons and positrons.} 
 scattering at small angles where a quasi real photon
 emitted by the incoming electron
 interacts with the proton.
The interaction of the partons of the quasi real photon and of the proton
 can lead to the process of so called prompt photon emission
 which is sensitive
 to their partonic substructures. 
%  Such interactions can lead to the emission of so called
%  prompt photons by the interacting partons of the proton
%  and the exchanged virtual photon and is therefore sensitive
% to their partonic structure.
 An isolated photon at large
  transverse energy \Etg can be related directly to the partonic event
  structure
 which is in contrast
   to jet measurements
   where the partonic structure is hidden behind the non perturbative
   hadronisation process. However, further information on the dynamics
  of the process can be obtained if prompt photons are measured
  together with jets. 
 
  Next to leading order (NLO) perturbative QCD (pQCD) calculations
   for inclusive production of isolated photons are
available
~\cite{Fontannaz:2001ek,Fontannaz:2001nq,Krawczyk:2001tz,Gordon:1994km}.
% where in leading order in $\alpha_s$ the
%   high $E_T$ photon is accompanied by a quark or gluon jet.
   In such calculations the exchanged photon interacts
   with the partons of the proton
 either directly
 or as a resolved photon. 
   The final state photon can be emitted in a hard partonic process
   or can be produced in a fragmentation process of a quark or gluon.

   In this paper,
 the previously
 reported results on
   inclusive prompt photon production~\cite{h1prel} are presented
   together with data where in addition to the photon a jet is detected. 
 We confront the measurements 
   with NLO calculations using the program of
   Fontannaz, Guillet and Heinrich
~\cite{Fontannaz:2001ek,Fontannaz:2001nq}
%~\cite{gudrun}.
   and with the event generator PYTHIA~\cite{Sjostrand:2000wi}
 based on leading order QCD matrix elements and 
  leading logarithmic parton showers.  
   The results are also compared to data of the
   ZEUS collaboration~\cite{Breitweg:1999su}.


\section{Strategy of Prompt Photon Measurement}

  Prompt photons are identified in the H1 liquid argon (LAr) 
  calorimeter~\cite{Andrieu:1993kh}.
  The main experimental difficulty is the separation of prompt photons 
  from hadronic background, in particular from 
  signals due to $\pi^0$ mesons, as for those, at high energies,
  the two energetic decay photons   
  cannot be resolved in the calorimeter.
  The $\pi^0$ mesons are predominantly produced in jets.
  Therefore an isolation requirement is applied
  for the $\gamma$ candidates.

  No track is allowed to point to the calorimetric energy cluster
  of the $\gamma$ candidate to exclude events in which the cluster
  is faked by electrons.
 Neutral current (NC)
  deep inelastic scattering (DIS) background events are further
  reduced by requiring a significant energy loss
 in the electron
  beam direction as
  expected in
% untagged
 photoproduction
  from the unmeasured energy of the electron
scattered under small angles.



  After all selection cuts, the background is still of similar size to
  the prompt photon signal.
  The signal is thus extracted exploiting a combination of
  discriminating shower
  shape functions.
% in a likelihood analysis.
  Distributions of the $\gamma$ candidates are fitted 
  by a sum of contributions of simulated photons, $\pi^0$ and $\eta$ mesons.
%  The signal extraction is performed independently in a  grid of
 This procedure is applied two-dimensionally in bins of 
 transverse energy \Etg and pseudorapidity $\eta^{\gamma}$.
  \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.}

  The data are corrected for detector effects by a detailed simulation
  of prompt photon production in the H1 detector based on the
  PYTHIA event generator~\cite{Sjostrand:2000wi}. 
  The $\pi^0$ and $\eta$ background estimate of PYTHIA is not used
 in the analysis.
  Only the $\eta/\pi^0$ fraction in the background
   ($ \approx 5\%$ after selection)
  is taken from the generator.
  
\section{Event Selection}

The data have been collected with the H1 detector~\cite{Abt:hi}
 at HERA in different data taking periods with electrons or positrons with
 energy $E_e = 27.6$ GeV collided with protons of energies
 $E_p = 820$ GeV or $E_p = 920$ GeV.
The data correspond 
to an integrated luminosity of $105~\pb^{-1}$ of which
 $28.8~\pb^{-1}$ and $61.3~\pb^{-1}$ are recorded in $e^+p$ interactions  
 at center of mass energies $\sqrt{s} = 301~\GeV$ and
 $\sqrt{s} = 319~\GeV$ respectively,
 and $14.9~\pb^{-1}$  in $e^-p$ interactions at $\sqrt{s} = 319~\GeV$.

The main experimental requirements for the event selection 
are the following:
\begin{itemize}
\item
The events are triggered by compact energy depositions in the LAr 
calorimeter.

\item 
A compact electromagnetic energy cluster,
consistent with a $\gamma$ shower,
 is reconstructed in the LAr 
calorimeter in the range \Etg $> 5$~GeV and $-1 < \eta^{\gamma} < 0.9$.
No track is allowed to point to this cluster within a distance of 25 cm.
 
\item
%Events with further calorimetric showers consistent with electrons, besides
%the $\gamma$ candidate, are rejected.
% shower sufficient for SPACAL, in LAr a track is needed for rejection.
Events with electron candidates are rejected,
 which restricts the virtuality of the exchanged photon
 to $Q^2 < 1$ GeV$^2$.


\item 
An event vertex is required to be within $\pm 35$ cm in $z$ 
 of the nominal vertex position
to remove non $ep$ background.

\item
At least two tracks in the central tracker are required, which assures
good vertex reconstruction and suppresses QED Compton background. 

\item
 For the inelasticity $y = 1 - E_e'/E_e$ we require
 $0.2 < y < 0.7$, where $E_e'$ is the energy of the non-detected scattered
 electron. The inelasticity is evaluated as $y = \sum{(E - p_z)}/2E_e$  
 where the sum runs over all detected final state particles.
  The range of  $y$ corresponds to 
 the $\gamma p$ center of mass energy range $142 < W < 266$~GeV at
 $E_p = 920$~GeV.
% The lower cut
% removes beam gas background, the upper cut reduces NC DIS background.

\item
 The $\gamma$ candidate is required to be isolated.
 The transverse energy, $E_T^{cone}$, in a cone
 around the $\gamma$ candidate, given by 
 distances below 1 unit in the  $(\eta - \phi)$ plane,
 is required not to exceed
 10\% of \Etg, 
 following the convention of~\cite{Breitweg:1999su}.

\item
 Associated jets are reconstructed using the inclusive $k_T$
 algorithm~\cite{Ellis:tq}
 with the conditions 
$E_T^{jet} > 4.5$ GeV
 and $-1 < \eta^{jet} < 2.3$ for the jet energy and pseudorapidity
 respectively. 
         
\end{itemize}

\section{Signal Extraction}

 A large fraction of the selected $\gamma$ candidates 
 have showers initiated by $\pi^0$ mesons.
 The fraction of prompt photons in the data is extracted by a shower
  shape analysis where 
 the mean transverse shower radius given by
      $R = \sum_{i} r_i \varepsilon_i / \sum_{i} \varepsilon_i$
 and the ``shower hot core
   fraction'' ($HCF$) are used to discriminate against background.
  Here $r_i$ is the transverse distance of  
   cell $i$ with energy density $\varepsilon_i$ measured 
   with respect to the axis from the event vertex to the center of gravity
   of the $\gamma$ candidate cluster.
   $HCF$ is the energy fraction 
   of the cluster which is contained in 4 or 8 contiguous cells
 including the cell of highest energy
  depending on calorimeter granularity.
 Discriminating functions
  based on the distributions of $R$ and $HCF$  
  are calculated for the data and
  for simulated samples of photons, $\pi^0$ mesons and $\eta$ mesons. 
  The contribution of the different particle types is then determined by
  fits  to the data distributions independently
 in $6 \times 6$ bins in $\eta^{\gamma}$ and $E_T^{\gamma}$.
 The $\eta/\pi^0$ fraction
  ($ \approx 5\%$ after selection) is taken from PYTHIA.     
   
%   Fig.~\ref{fig:signal} shows for the example of one $(\eta,E_T)$ bin
  The measured distributions of $R$ and $HCF$
 for the full $\eta^{\gamma}$, \Etg range
 are shown in Fig.~\ref{fig:signal}
  together with the simulated 
   distributions of photons and background from $\pi^0$ and $\eta$ mesons.
  For the latter the normalisations are taken from the discriminating fits
   described above.
 The data distribution is well
   described by the extracted signal and background components.
   The discrimination power
   decreases at
   high \Etg where the $R$ and $HCF$ distributions
   of $\pi^0$ mesons and photons get more similar.
    Therefore events with \Etg $> 10$ GeV are not included
  in the results presented below. 

\section{Systematic Uncertainties}


 For the prompt photon cross sections various systematic uncertainties  
 were considered and the total systematic errors are obtained 
 by adding the different systematic errors in quadrature.

\begin{itemize}

\item
   The most important systematic errors are due to imperfections in the 
  simulation of the shower shapes.
Uncertainties in the simulated distributions of $R$ and $HCF$ have been
estimated by comparing simulations of electrons with electron candidates
in NC DIS events. Differences in these distributions have been quantified
 resulting in errors on the cross sections ranging from
 $\pm 10\%$  to $\pm 20\%$. 
% Uncertainties in the simulated
%  distributions of $R$ and $HCF$ 
%  are established by comparison to electron candidates from NC DIS events.
%  The resulting errors of the cross sections are typically
% $\pm 10\%$  to $\pm 20\%$. 

\item 
 The uncertainties on the calorimeter electromagnetic and hadronic
 energy scales
% and variations of the
%assumed $E_T$ and $\eta$ dependence of the single particles used in
%  the shower simulations
 contribute errors of about 5\% to the inclusive cross sections.
  For the case of associated jets the hadronic energy uncertainty
  contributes about 10\%.
 
\item
   Background due to DIS electrons
 resulting from  the tracker inefficiency
  (below 0.4\% for the track selection used)
   leads to
   a subtraction of 3.0\% 
 with an uncertainty of $\pm 0.3\%$
    in the lowest $\eta$ bin and at
   high \Etg , and is negligible otherwise.  

\item
   An  overall normalisation uncertainty
  of $\pm 1.5\%$ on the luminosity measurement is not
   included in the results.

\item
   To take account of model dependencies in the detector corrections,
   which are determined
   by simulation of the measurement using PYTHIA,
   the shape of the \Etg dependence in PYTHIA is varied leading to
   uncertainties below 3\%.
   Also the sensitivity of the detector corrections to the
   underlying event activity in PYTHIA is studied by changing
   the relative
%   weight of the PYTHIA events as function of
   weight of the PYTHIA events in proportion to
   the transverse energy $E_T^{cone}$
   in the isolation cone around the photon.
  Allowing a change for the relative event yield at the cut energy
        $E_T^{cone} = 0.1 \cdot E_T^{\gamma}$
by factors 0.5 and 2
 leads to variations of the
   final results below 3\% which are included in the systematic
errors.
 It was verified that PYTHIA gives a good description of the dependence
  of the measured cross sections on the chosen cut on the isolation cone.
% Finally, switching off the multiple interactions in PYTHIA changes
% the resulting measured cross sections by less than $ \%$.
 
\end{itemize}
     
\section{Results}
  The results are presented as $ep$ cross sections 
 \footnote{The cross sections obtained
    at $\sqrt{s} = 301~\GeV$
   are transformed to  $\sqrt{s} = 319~\GeV$
by corrections of about $+4\%$ taken from PYTHIA.} for 
\begin{displaymath}
\sqrt{s} = 319~\GeV, \; \; 0.2 < y < 0.7, \; 
 \; Q^2 < 1 \; \GeV^2, \;
    5 < E_T^{\gamma} < 10 \; \GeV, \; -1 < \eta^{\gamma} < 0.9  
\end{displaymath}
\begin{displaymath}
  {\rm including \; the \; photon \; isolation \; condition}
 \; E_T^{cone} < 0.1 \; \cdot E_T^{\gamma}.
\end{displaymath}
The errors in the figures contain the statistical errors as obtained from 
the shower discriminating fits and the systematic errors added in quadrature. 

    Inclusive differential cross sections \dsdE and \dsdeta
    are shown in Fig.~\ref{fig:res} and compared to
    the NLO pQCD calculation
 of Fontannaz et al.~\cite{Fontannaz:2001ek}
%~\cite{gudrun}  
  and the PYTHIA event generator~\cite{Sjostrand:2000wi}.
    In the NLO calculation \Etg is used for the renormalisation
 and the factorisation scales.
 The photon and proton parton densities
    AFG~\cite{Aurenche:1994in}
  and MRST2~\cite{Martin:1999ww}
    are used respectively.
  In PYTHIA the leading order QCD matrix elements are regulated by a minimum
    cut-off in transverse momentum which is set to 3~GeV. 
    The parton densities
     GRV(LO)~\cite{Gluck:1991jc,Gluck:1994uf} are used 
    for the photon and proton.
    The program simulates 
    multiple parton interactions (MI) and initial and final state
 QED and QCD radiation
\footnote{PYTHIA 6.15/70 was used with default parameters except
$<k_T^2> = 1$ GeV$^2$ for
 the intrinsic $k_T$ of initial state
    partons in the proton.}.

 The NLO calculation describes the data quite well
 in the presented \Etg and $\eta^{\gamma}$ ranges with a tendency
 to overshoot the data 
 at large $\eta^{\gamma}$.
 The PYTHIA simulation describes the data well in shape,
   but is low by about 30\% in normalisation.
  For comparison we show in Fig.~\ref{fig:pythia} also the PYTHIA
  prediction without multiple interactions. 
 It is interesting to note that in this case the predictions 
  at $0 <$ \etag $< 0.9$ are about 25\% higher, showing that
  the cross section is reduced by the soft underlying event activity,
 as expected~\cite{Fontannaz:2001ek} 
  due to the isolation condition. 
%   $E_T^{cone} = 0.1 \; \cdot E_T^{\gamma}$.
  Fig.~\ref{fig:pythia} shows the full PYTHIA prediction 
  with and without MI, as well as the separate
  contributions of
  resolved interactions of the exchanged photon
  and of photon radiation
   from a final state quark in di-jet events.

   The data are compared\footnote{The H1 data
   are corrected for the extension of the upper limit in $y$ from 0.7 to 0.9
   using PYTHIA.}
   to the results of the ZEUS collaboration
   in  Fig.~\ref{fig:resZ} at $\sqrt{s} = 301~\GeV$ in the range
    $-0.7 < \eta^{\gamma} < 0.9$ and $0.2 < y < 0.9$.
   The data are consistent, but the H1 data are somewhat lower at small
   $\eta^{\gamma}$, where the ZEUS results appear to exceed the 
   NLO calculation.
    
 Cross sections for a prompt photon together with a jet are presented
 in Fig.~\ref{NLOscale} as a function of the variables
    $E_T^{\gamma}, \eta^{\gamma}, E_T^{jet}, \eta^{jet}, x_p$ and
 $x_{\gamma}$, where
 $x^{p} = (E_T^{jet}e^{\eta^{jet}}+ E_T^{\gamma}e^{\eta^{\gamma}})/2E_p$ and
 $x_{\gamma}=(E_T^{jet}e^{-\eta^{jet}}+ E_T^{\gamma}e^{-\eta^{\gamma}})/2yE_e$
  correspond to
  the energy fractions of the incident proton and
 exchanged photon, respectively, participating in the hard process.
The NLO corrections are substantial and lead to a good description 
of the data. 
 Taking into account the multiple interaction effects, as expected
 on the basis of PYTHIA, improves the data description
 in particular at   $\eta^{\gamma} > 0$ and $x_{\gamma} < 0.5$.
 No corrections have been made to the NLO prediction for hadronisation
 effects.

 A measurement with jet energy 
 $E_{T,min}^{jet} = 5$ GeV is shown differentially in \Etg in 
 Fig.~\ref{sym}. As also observed in dijet analyses, the data
 can not be directly described by  NLO calculations
 in the region of symmetric cuts
 $E_{T,min}^{jet} = E_{T,min}^{\gamma}$.
 Infrared instabilities
 lead to an unphysical drop of the calculated NLO cross section
 near the cut value,
 as discussed in~\cite{Fontannaz:2001nq}.
  
 
\section{Conclusions}

 Photoproduction of prompt photons,
    both, inclusively and 
    associated with jets, has been studied.
 The data are quite well described in the
 kinematic range covered
  by a NLO pQCD calculation, but the prediction is above the data
  in the forward region (\etag $> 0.6$) which may be related to 
  underlying event activity not contained in the NLO calculation.
  The cross sections produced with the 
  PYTHIA event generator describe the data distribution well in shape
  with a normalisation that is about 30\% low.
The presented inclusive prompt photon cross sections
\dsdE and \dsdeta 
 are in broad agreement with results from the ZEUS
collaboration, but tend to be lower at negative \etag.

%  The cross sections for prompt photons together with a jet
%  are well described by the NLO calculation, in particular if
%  multiple interactions
%% as expected by the PYTHIA generator
%  are taken into account. The NLO corrections are large in some regions
%  and are needed to describe the data.

\vspace*{14.25pt}

\noindent {\large \bf Acknowledgements}

\noindent
 We are grateful to Gudrun Heinrich for discussions and for providing
 some results of the NLO QCD calculations. 
%
%   References 
%
\begin{thebibliography}{99}
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\bibitem{Fontannaz:2001ek}
M.~Fontannaz, J.~P.~Guillet and G.~Heinrich,
%``Isolated prompt photon photoproduction at NLO,''
Eur.\ Phys.\ J.\ C {\bf 21} (2001) 303   
[arXiv:hep-ph/0105121].  
%%CITATION = HEP-PH 0105121;%%

%\cite{Fontannaz:2001nq}
\bibitem{Fontannaz:2001nq}
M.~Fontannaz, J.~P.~Guillet and G.~Heinrich,
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Eur.\ Phys.\ J.\ C {\bf 22} (2001) 303
[arXiv:hep-ph/0107262].
%%CITATION = HEP-PH 0107262;%%

%\cite{Krawczyk:2001tz}
\bibitem{Krawczyk:2001tz}
M.~Krawczyk and A.~Zembrzuski,
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%%CITATION = HEP-PH 0105166;%%

%\cite{Gordon:1994km}
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%%CITATION = PHRVA,D52,58;%%

%\bibitem{gudrun}
%Gudrun Heinrich, private communication.

%\cite{h1prel}
\bibitem{h1prel}
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%\cite{Sjostrand:2000wi}
\bibitem{Sjostrand:2000wi}
T.~Sj\"ostrand, P.~Ed\'en, C.~Friberg, L.~L\"onnblad, G.~Miu,
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%%CITATION = HEP-PH 0010017;%%

%\cite{Breitweg:1999su}
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%\cite{Chekanov:2001aq}
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%%CITATION = HEP-EX 0104001;%%


%\cite{Andrieu:1993kh}
\bibitem{Andrieu:1993kh}
B.~Andrieu {\it et al.}  [H1 Calorimeter Group Collaboration],
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%%CITATION = NUIMA,A336,460;%%

%\cite{Abt:hi}
\bibitem{Abt:hi}
I.~Abt {\it et al.}  [H1 Collaboration],
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Nucl.\ Instrum.\ Meth.\ A {\bf 386} (1997) 310;
%%CITATION = NUIMA,A386,310;%%
%\cite{Abt:1996xv}
%\bibitem{Abt:1996xv}
%I.~Abt {\it et al.}  [H1 Collaboration],
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%Nucl.\ Instrum.\ Meth.\ A {\bf 386} (1997) 348.
ibid. A {\bf 386} (1997) 348.
%%CITATION = NUIMA,A386,348;%%

%\cite{Ellis:tq}
\bibitem{Ellis:tq}
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%%CITATION = HEP-PH 9305266;%%

%\cite{Aurenche:1994in}
\bibitem{Aurenche:1994in}
P.~Aurenche, J.~P.~Guillet and M.~Fontannaz,
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Z.\ Phys.\ C {\bf 64} (1994) 621
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%%CITATION = HEP-PH 9406382;%%

%\cite{Martin:1999ww}
\bibitem{Martin:1999ww}
A.~D.~Martin, R.~G.~Roberts, W.~J.~Stirling and R.~S.~Thorne,
%``Parton distributions and the LHC: W and Z production,''
Eur.\ Phys.\ J.\ C {\bf 14} (2000) 133
[arXiv:hep-ph/9907231].
%%CITATION = HEP-PH 9907231;%%

%\cite{Gl\uck:1991jc}
\bibitem{Gluck:1991jc}
M.~Gl\"uck, E.~Reya and A.~Vogt,
%``Photonic parton distributions,''
Phys.\ Rev.\ D {\bf 46}, 1973 (1992).
%%CITATION = PHRVA,D46,1973;%%

%\cite{Gluck:1994uf}
\bibitem{Gluck:1994uf}
M.~Gl\"uck, E.~Reya and A.~Vogt,
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Z.\ Phys.\ C {\bf 67} (1995) 433.
%%CITATION = ZEPYA,C67,433;%%

\end{thebibliography}

\begin{figure}[p] \unitlength 1pt 
 \begin{center}
\begin{picture}(200,200)
   \put(-130,-15.){\epsfig{file=H1prelim-02-152.fig1a.eps,width=200pt}}
   \put(100,-15.){\epsfig{file=H1prelim-02-152.fig1b.eps,width=200pt}}
 \end{picture}
  \end{center}
  \caption{Distributions of the mean transverse shower radius $R$ (a) and 
   and the hot core fraction $HCF$ (b) for the selected photon candidates
   (data points) for the full range
   $ -1 < \eta < 0.9, \; 5 < E_T^{\gamma} < 10$ GeV.
  Also shown are the results of the fit (solid lines) by the 
  extracted contributions of photons (dashed lines) and
     background ($\pi^0 + \eta$, dotted lines) (see text).}
  \label{fig:signal}
\end{figure} 

\begin{figure}[ht] \unitlength 1pt 
  \begin{center}
\begin{picture}(200,200)
   \put(-130,-15.){\epsfig{file=H1prelim-02-152.fig2a.eps,width=200pt}}
   \put(100,-15.){\epsfig{file=H1prelim-02-152.fig2b.eps,width=200pt}}
 \end{picture}
  \end{center}
  \caption{Inclusive prompt photon differential cross sections
\dsdE for  $-1 < \eta^{\gamma} < 0.9$ (a)
and \dsdeta for $5 <$ \Etg $< 10$ GeV (b)
 at $\sqrt{s} = 319~\GeV$ and $0.2 < y < 0.7$    
compared to the prediction of  
a NLO pQCD calculation~\cite{Fontannaz:2001ek}
and the PYTHIA generator~\cite{Sjostrand:2000wi}.}
  \label{fig:res}
\end{figure} 

\begin{figure}[ht] \unitlength 1pt 
 \begin{center}
\begin{picture}(200,200)
   \put(-130,-15.){\epsfig{file=H1prelim-02-152.fig3a.eps,width=200pt}}
   \put(100,-15.){\epsfig{file=H1prelim-02-152.fig3b.eps,width=200pt}}
 \end{picture}
  \end{center}
  \caption{Inclusive prompt photon differential cross sections
\dsdE for  $-1 < \eta^{\gamma} < 0.9$ (a)
and \dsdeta for $5 <$ \Etg $< 10$ GeV (b)
 at $\sqrt{s} = 319~\GeV$ and $0.2 < y < 0.7$
 compared to the PYTHIA prediction including multiple interactions
 (full line),
 with the contributions from di-jet events where a final state
 quark radiates a photon (dashed-dotted) and this component summed with resolved 
 photon events (dotted line). Also shown is the the full
  PYTHIA prediction without multiple interactions (dashed line).
}
  \label{fig:pythia}
\end{figure} 

%

\begin{figure}[ht] \unitlength 1pt  
  \begin{center}
\begin{picture}(200,200)
   \put(-130,-15.){\epsfig{file=H1prelim-02-152.fig4a.eps,width=200pt}}
    \put(100,-15.){\epsfig{file=H1prelim-02-152.fig4b.eps,width=200pt}}
 \end{picture}
  \end{center}
  \caption{Inclusive prompt photon differential cross sections
    \dsdE for  $-0.7 < \eta^{\gamma} < 0.9$ (a)
  and \dsdeta for $5 <$ \Etg $< 10$ GeV (b) corrected to 
 $\sqrt{s} = 301~\GeV$ and $0.2 < y < 0.9$,  
compared to results of the ZEUS collaboration~\cite{Breitweg:1999su}. 
Also shown is the prediction of  
a NLO pQCD calculation~\cite{Fontannaz:2001ek}.}
  \label{fig:resZ}
\end{figure} 


\clearpage

\begin{figure}[ht] \unitlength 1pt
\begin{center}
\begin{picture}(200,580)
   \put(-80,20){\epsfig{file=H1prelim-03-035.fig1.eps,width=350pt}}
 \end{picture}
\caption{
Prompt photon differential cross sections with an additional jet requirement
  ($E_T^{jet} > 4.5$ GeV)
 as a function of
$E_T^{\gamma}$, $\eta^{\gamma}$, $E_T^{jet}$, $\eta^{jet}$, $x_{\gamma}$,
 and $x_p$.
The data are compared with pQCD in LO (dashed line) and NLO
~\cite{Fontannaz:2001ek,Fontannaz:2001nq}.
 The error bands show the 
 effect of a variation of the renormalisation and factorisation scales
  in the NLO calculation from $0.5 \cdot E_T^{\gamma}$
 to $2 \cdot E_T^{\gamma}$. Also shown is the NLO result 
 corrected by PYTHIA for
  multiple interaction effects (NLO QCD (M.I.), dotted line).
}
 \label {NLOscale}
\end{center}
\end{figure}

\clearpage

\begin{figure}[ht] \unitlength 1pt
\begin{center}
\begin{picture}(200,500)
   \put(-90,0){\epsfig{file=H1prelim-03-035.fig2.eps,width=300pt}}
 \end{picture}
\caption{
Prompt photon differential cross sections with a jet requirement
 as function of
$E_T^{\gamma}$ with 
 $E_{T,min}^{jet} = E_{T,min}^{\gamma} = 5$ GeV.
The data are compared with pQCD LO (dashed line) and NLO (solid line)
~\cite{Fontannaz:2001ek,Fontannaz:2001nq}.
}
 \label {sym}
\end{center}
\end{figure}

\end{document}




