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\begin{document}

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\begin{titlepage}

%\noindent
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%%{\it {\large version of \today}} \\[.3em] 
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%%Submitted to & \multicolumn{3}{r}{\footnotesize Electronic Access: {\it http://www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em] \hline 
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%\multicolumn{4}{l}{{\bf
%                 15th International Workshop on Deep Inelastic Scattering,
%                 DIS2007, March 15-20, 2007, Munich, Germany}} \\
%                 & Abstract:        & {\bf xx-xxx}    &\\
%                 & Parallel Session & {\bf x}   &\\ \hline
% & \multicolumn{3}{r}{\footnotesize {\it
%    www-h1.desy.de/h1/www/publications/conf/conf\_list.html}} \\[.2em]
% & \multicolumn{3}{r}{H1prelim-07-064} \\[.2em]
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\vspace*{5cm}

\begin{center}
  \Large
  {\bf 
    Search for Events with Isolated Tau Leptons \\  
    and Missing Transverse Momentum at HERA \\ 
%    {\boldmath $e q$} 
    }

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

\begin{abstract}

\noindent
A search for the production of tau leptons in $ep$ collisions 
with the H1 detector at HERA is presented. A data sample corresponding 
to a total integrated luminosity of $471~pb^{-1}$ taken in the years 
1994-2007 is analysed,
representing the full HERA~I+II high-energy data set.
%which includes recent data collected in the period 2003-2007 (HERA-II), 
%where 182 pb$^{-1}$ of $e^+p$ data and 170 $e^-p$ data were taken.
Tau leptons are identified using an 
identification algorithm based on the search for isolated charged
tracks associated to narrow hadronic jets detected in the 
calorimeters, a typical signature of the one-prong hadronic tau decay. 
In the region where the hadronic system~($X$) has a transverse
momentum $P_T^X>25~\GeV$ one event is observed in the data where the
Standard Model (SM) expectation is  $0.99 \pm 0.13$ events.

\end{abstract}


\end{titlepage}

\pagestyle{plain}

\section{Introduction}

Events with isolated tau lepton candidates and missing transverse momentum 
are selected in $ep$~collisions in the full HERA I+II high-energy data sample 
corresponding to an integrated luminosity of $471~\mbox{pb}^{-1}$. 
This includes $287~\mbox{pb}^{-1}$ of $e^{+}p$ data and 
$184~\mbox{pb}^{-1}$ of $e^{-}p$ data.

%\cite{isolAndreev2003}

The selection, summarised in Tab.~1, is based on the one used in the 
search for events 
with tau leptons and missing transverse momentum ($P_{T}^{{\rm miss}}$) in 
HERA I data, included in the paper on tau lepton production in $ep$ collisions
\cite{tauHERA1}. 
Improvements to the tau identification algorithm,
in particular the track isolation, require the reanalysis of all data.
In the final sample, 20 events are selected where $19.5 \pm 3.2$ are expected
in the SM framework. The SM expectation is dominated by charged current events.
At $P_T^X > 25$ GeV one event, shown in~Fig.~4 (previously shown 
in~\cite{isotauDIS06}), is selected while $0.99 \pm 0.13$ are expected in the SM. 
In this region the contribution
of real $W$ production to the SM expectation, considered signal in this
analysis, is about $60\%$.
%The results in \cite{tauHERA1} and the previous preliminary update 
%\cite{isotauDIS06} are superseded by the results presented here.

This search complements the observation 
of isolated electrons and muons in events with missing transverse momentum 
in $ep$ collisions at HERA I+II \cite{isolAndreev2003,isolepDIS07}.


\begin{thebibliography}{99}

% H1 tau paper
\bibitem{tauHERA1}
A.~Aktas {\em et al.} [H1~Collaboration], {\it Tau Lepton Production 
in $ep$ Collisions at HERA},
Eur.Phys.J.C, {\bf C}48 (2006) 699-714, 04/06, [hep-ex/0604022].

% DIS 06 tau
\bibitem{isotauDIS06}
H1 Collaboration; {\it Search for Events with Tau Leptons at HERA},
[H1prelim-06-064].
%contributed paper to {\it Deep Inelastic Scattering}, Tsukuba 2006, {\bf Abstract xxx}.

% H1 IsoLep paper
\bibitem{isolAndreev2003} 
V.~Andreev {\em et al.} [H1 collaboration],
Phys. Lett. B~{\bf 561} (2003) 241 [hep-ex/0301030].

\bibitem{isolepDIS07}
H1 Collaboration; {\it Search for Events with Isolated Leptons and Missing Transverse Momentum at HERA},
[H1prelim-07-063].
%contributed paper to {\it Deep Inelastic Scattering}, Munich 2007, {\bf Abstract xxx}.






          
\end{thebibliography}

\begin{table}
\renewcommand{\arraystretch}{1.4}

\begin{center}\begin{tabular}{|c|c|}
%\hline 
%\multicolumn{2}{c}{\textsf{\textbf{Tau Channel Selection}}}\tabularnewline
%\hline
\hline 
\textbf{Inclusive CC}&
$P_{T}^{\mbox{calo}}>12$~GeV\tabularnewline
&
$P_{T}^{\mbox{had}}>12$~GeV\tabularnewline
&
$P_{T}^{\mbox{miss}}>12$~GeV\tabularnewline
&
$\delta^{\mbox{miss}}>5$~GeV\tabularnewline
&
$V_{ap}/V_{p}<0.5$\tabularnewline
&
($<0.15$ if $P_{T}^{\mbox{miss}}<25$~GeV)\tabularnewline
\hline
\hline 
\textbf{Narrow Jets}&
$P_{T}^{jet}>7$~GeV\tabularnewline
&
$20°<\theta^{jet}<120°$\tabularnewline
&
$R^{jet}<0.12$\tabularnewline
&
$N_{tracks}^{jet}\geq1$, max($P_{T}^{track})>5$ GeV\tabularnewline
Isolation&
$D_{em,\mu,jet}>1.0$\tabularnewline
Acoplanarity&
$\Delta\varphi(\tau,X)<170°$ if $P_{T}^{X}>5$~GeV\tabularnewline
\hline
\textbf{1-Prong Jets}&
$N_{tracks}^{Djet<1.0}=1$\tabularnewline
\hline
\textbf{Final Selection}&
$N_{\textrm{DTNV}}^{D_{track}<0.3}=1$\tabularnewline
\hline
\end{tabular}\end{center}


\caption{\label{tab:TauJetSelection}{Summary of selection requirements for
isolated tau jets in events with $P_T^{\mbox{miss}}$ . 
$N_{tracks}^{Djet<1.0}$ denotes the number of high-quality tracks in
a cone of 1.0 in the $\eta-\varphi-$plane around the jet-axis.
$N_{\textrm{DTNV}}^{D_{track}}$ denotes the number of non-vertex-fitted
track segments in a cone of 0.3 in the $\eta-\varphi-$plane around the
high-quality track.}}
\end{table}


\clearpage

\begin{table}
  \renewcommand{\arraystretch}{1.5} 
  \begin{center}

\input{H1prelim-07-064.fig0.tex}

\caption{Summary of the H1 search for events with tau leptons and missing 
        transverse momentum for the $e^{+}p$ data
	($\cal L$=287 pb$^{-1}$), $e^{-}p$ data ($\cal L$=184 pb$^{-1}$) and 
        the full HERA data set ($\cal L$=471 pb$^{-1}$).
        The results are shown for the full selected sample and for the 
        subsample at $P_{T}^{X}>25$~GeV. 
        The number of observed events is compared to the SM prediction. 
        The SM signal (W decay into tau) 
        and the background contributions are also shown.
        The quoted errors contain statistical and systematic uncertainties 
        added in quadrature.}
  \end{center}
\end{table}


%\clearpage

\begin{figure}[ht] 
  \begin{center}
      \includegraphics[width=15cm]{H1prelim-07-064.fig1.eps}
  \end{center}
  \caption{The hadronic transverse momentum distribution of 
    $\tau + P_T^{\rm miss}$ events in
    HERA $e^{+}p$ data (${\cal L}=287$~pb$^{-1}$) is compared to the SM
    expectation (open histogram).  The signal component of the SM
    expectation, dominated by real $W$ production, is given by the
    hatched histogram. $\rm N_{Data}$ is the total number of data
    events observed, $\rm N_{SM}$ is the total SM expectation. The
    total error on the SM expectation is given by the shaded band.}
  \label{fig:ptxheraposi}
\end{figure} 

\begin{figure}[ht] 
  \begin{center}
      \includegraphics[width=15cm]{H1prelim-07-064.fig2.eps}
  \end{center}
  \caption{The hadronic transverse momentum distribution of 
    $\tau + P_T^{\rm miss}$ events in
    HERA $e^{-}p$ data (${\cal L}=184$~pb$^{-1}$) is compared to the SM
    expectation (open histogram).  The signal component of the SM
    expectation, dominated by real $W$ production, is given by the
    hatched histogram. $\rm N_{Data}$ is the total number of data
    events observed, $\rm N_{SM}$ is the total SM expectation. The
    total error on the SM expectation is given by the shaded band.}
  \label{fig:ptxheraelec}
\end{figure} 

\begin{figure}[ht] 
  \begin{center}
      \includegraphics[width=15cm]{H1prelim-07-064.fig3.eps}
  \end{center}
  \caption{The hadronic transverse momentum distribution of 
    $\tau + P_T^{\rm miss}$ events in
    HERA $e^{\pm}p$ data (${\cal L}=278$~pb$^{-1}$) is compared to the SM
    expectation (open histogram).  The signal component of the SM
    expectation, dominated by real $W$ production, is given by the
    hatched histogram. $\rm N_{Data}$ is the total number of data
    events observed, $\rm N_{SM}$ is the total SM expectation. The
    total error on the SM expectation is given by the shaded band.}
  \label{fig:ptxheraall}
\end{figure} 

\begin{figure}[htp] 
  \begin{center}
\epsfig{file = H1prelim-07-064.fig4.eps, width=14cm }
  \end{center}
  \caption{Candidate event with an isolated tau and $P_T^\mathrm{miss}$ containing a prominent \newline hadronic system $X$.}
  \label{fig:taucand1}
\end{figure} 

%\begin{figure}[ht] 
%  \begin{center}
%\epsfig{file =TAUED.R432176.E46606.eps, width=17cm }
%  \end{center}
%  \caption{Candidate event with isolated tau and $P_T^\mathrm{miss}$ containing a prominent \newline hadronic system $X$.}
%  \label{fig:taucand2}
%\end{figure} 

%\begin{figure}[ht] 
%  \begin{center}
%\epsfig{file =TAUED.R434722.E135181.eps, width=17cm }
%  \end{center}
%  \caption{Candidate event with isolated tau and $P_T^\mathrm{miss}$ containing a prominent \newline hadronic system $X$.}
%  \label{fig:taucand3}
%\end{figure} 

\end{document}

