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Algorithm

The new cluster-track matching program first identify electrons and muons with external particle-ID devices. Then EM-cluster-$e^\pm$-track matching is performed which is followed by HD-cluster-hadron-track matching. The cluster-track matching proceeds as follows. We first form global calorimetric clusters, which are contiguous calorimeter blocks with nonzero energy deposites (see Fig.1.1).


 
Figure 1.1:  Global cluster and corresponding tracks
\begin{figure}
\centerline{
\epsfxsize=8cm 
\epsfbox{gcluster.epsf}}\end{figure}

When such a global cluster contains no matched charged track, the cluster is recognized as a pure neutral particle and we assign a 4-momentum:
\begin{displaymath}
\begin{array}
{lll}
 E^{N\mu} = (E^G, E^G \cdot \bar{{\bf x}}_G/\left\vert\bar{{\bf x}}_G\right\vert)\end{array}\end{displaymath} (1)
assuming it is a single massless neutral particle.

On the other hand, when the energy of the global cluster EG is consistent with the energy of the corresponding charged tracks EC:
\begin{displaymath}
\begin{array}
{lll}
 E^G - E^C \le n \cdot \sigma,\end{array}\end{displaymath} (2)
the global cluster is taken as consisting entirely of charged particles. We thus discard this global cluster and use only tracking information.

When the above matching condition is not satisfied:
\begin{displaymath}
\begin{array}
{lll}
 E^G - E^C \gt n \cdot \sigma,\end{array}\end{displaymath} (3)
the global cluster is recognized as a mixed cluster consisting of both charged and neutral particles. In this case, we use all the charged tracks in this global cluster, while treating the energy difference as a single massless neutral particle with a 4-momentum:
\begin{displaymath}
\begin{array}
{lll}
 E^{N\mu} = (E^N,{\bf E}^N),\end{array}\end{displaymath} (4)
where
\begin{displaymath}
\begin{array}
{lll}
 E^N & = & E^G - E^C \cr
 {\bf E}^N 
 & ...
 ...- \sum \vert{\bf p}_i\vert {\bf x}_i^p\right\vert }.\end{array}\end{displaymath} (5)


next up previous
Next: Usage Up: Philosophy Previous: overview
Keisuke Fujii
12/3/1998