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\title{On the Time Resolution of the BCAL and Its Dependence on Pulse Height}
\author{R.T. Jones \\
University of Connecticut, Storrs, CT}
\date{October 6, 2007}
\maketitle
\vspace{2cm}
\begin{abstract}
The GlueX barrel calorimeter (BCAL) plays a dual role as an electromagnetic
calorimeter and as a time-of-flight detector for charged particles.  The
time resolution of the BCAL is important for its performance in both roles.
A simple statistical model of the time resolution is presented.  A
fundamental link between photoelectron statistics and time resolution
is demonstrated.
\end{abstract}

\newpage

\section{Leading Edge Timing}

Two methods are commonly used to extract accurate leading-edge timing
information from a scintillation pulse.  The first method employs a
constant-voltage discriminator whose output transitions when the input
pulse rises through a fixed threshold that is set as low as possible for
optimal time resolution, typically a few sigma above the electronic noise.
The second method uses a constant-fraction discriminator which transitions
at the point where the leading edge of the pulse rises through a fixed
fraction of its total pulse height.  In either case, a second discriminator
with a fixed second threshold is often used in combination with the first,
to provide a hit pattern based on a flexible threshold. 

\section{Statistical Model}
\section{Results and Discussion}

\begin{thebibliography}{d}
\bibitem{gluex-804} B.~Leverington, ``Analysis of the BCAL Hall-B Beam test'', 
{\em gluex-doc-804} 2007;
\bibitem{gluex-840} Z.~Papandreou, ``BCAL Calorimetry Response'',
{\em gluex-doc-840} 2007.
\bibitem{gluex-842} B.~Leverington, G.~Lolos, Z.~Papandreou, A.~Semenov,
S.~Katasaganis, C.~Kourkoumeli, A.~Dzierba, and D.~Lawrence, ''BCAL Facts:
What we know and how we know'', {\em gluex-doc-842} 2007.
\end{thebibliography}

\end{document}
