

\subsection{\bf Examples of Correlations}
\subsection{\bf 2D Track Finding---II}

\begin{slide}
\begin{itemize}
\item (Note:  If $\sigma_1 = \sigma_2$ and $z_1 = -z_2$, i.e., origin
$z$ midpoint between chambers, then $a$ and $b$ are uncorrelated.)

\item However, the origin, $z=0$ (in our experiment E110 at Fermilab),
was a convenient surveyor's mark and so was not chosen to minimize
correlation.

\item In the case of many measurement chambers, the slope and
intercept will still be correlated but there will be no simple way to get
rid of it.  

\item In practice, it is important to keep {\bf full\/} correlation
matrix. 

\item For instance, estimation of best vertex from intersection of
several tracks needs the full matrix.
\end{itemize}

\vspace*{10pt}
\centerline{\psfig{figure=fig5.phys.ps,clip=true,width=4.0in}}
\vspace*{10pt}
\end{slide}

