When we started using the test beam, we performed an high voltage scan in order to find the tracker chambers working point. At first we computed its efficiency without checking whether the clusters corresponded to actual tracks, since we already knew from previous tests that the tracker was reliable.\\

We verified the relationships between efficiency and threshold, and between the average size of hit clusters and the threshold; these measurements were carried out after finding the right latency. \figurename~\vref{prel-trk} shows the results.\\

\begin{figure}
	\centering
	\subfigure[Efficiency VS threshold]
	{\includegraphics[width=6.6cm]{Images/tracker/trk-th-nocolors}\label{trk-th}}
	\hspace{2mm}
	\subfigure[Cluster size VS threshold]
	{\includegraphics[width=6.6cm]{Images/tracker/trk-cl-nocolors}\label{trk-cl}}
	\vspace{2mm}
	\subfigure[Efficiency VS latency]
	{\includegraphics[width=6.6cm]{Images/tracker/trk-lat-nocolors}\label{trk-lat}}
	\caption{Preliminary tracker tests}
	\label{prel-trk}
\end{figure}