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Subsections
In the quick simulator, following algorithm is used to clusterize hit cell information
of elemag calorimeter. Note that for hadron calorimeter,
another algorithm for track-cluster matching
developed by Keisuke Fujii is used without clustering of
calorimeter's hit cell..
- 1.
- Find highest energy counter BL1 whose energy larger than ETH.
- 2.
- Find neighbor counter BL2 and include in the cluster.
- 3.
- Find BL3 that is neighbour counter of BL2, include in the cluster
if one of the following two conditions is satisfied.
- (a)
-
- (b)
-
(ETH, c1, c2, c3) are parameters to be optimized for each detector geometry.
To find out optimum value of clustering parameters,
we generated two photons whose opening angle is some fixed value and
study the efficiency to be clustered to two clusters. The energy
of photon is generated randomly in betwen 1 GeV to 50 GeV
and
range is from -0.7 to 0.7 so as to cover barrel
Elemag calorimeter region. The azimuthal angle is from 0 to 360.
The obtained figure is shown in Fig. 4. In this figure,
the opening angle of two photon is 50mrad.
Figure 4:
The efficiency to cluster into two cluster
when two photons are generated. The opening angle between two photons
is fixed at 50 mrad. The energy of two photons are same, but
changes event by event between 1 to 50 GeV.
|
Figure 5:
Same as Fig. 4, but with 100 mrad opening angle
between photons.
|
Figure 6:
The efficiency to cluster to one
when one photon is generated. The energy of photon is same, but
changes event by event between 1 to 50 GeV.
|
Figure:
Same as Fig. 4 for
the case of Endcap Elemeg Calorimeter. First photon is generated
with the
range from 0.79 to 0.96. Second photon
is generated with the opening angle of 50 mrad and same energy.
|
Figure 8:
Same as Fig. 7, but with 100 mrad opening angle
between photons.
|
Figure 9:
The efficiency to cluster to one
when one photon is generated. The energy and the angular range is same
as Fig. 7.
|
For 1 photon reconstruction in Barrel EM calorimeter(Fig. 6),
,
,
for high efficient
clustering. For two photons with 100 mrad separation in Barrel EM calorimeter
(Fig. 5),
requirement to the clustering parameters for efficient clustering is,
0.3 < c1 < 0.5, c2 > 0.2, c3 > 0.5.
Parameters of EM calorimeters are summarized in the Fig. 10.
Figure 10:
parameters of EM calorimeter.
|
As seen in the figure, phi segmentation is about 25 mrad. Therefore,
if opening angle between two photon is 50 mrad, EM hit cell is quite
over lap and it is hard to separate them with high efficiency.
It requires about 100 mrad separation to high efficient cluster separation.
As a conclusion, current default value of clustering is good for both
barrel and end cap EMC calorimeter.
Next: Tuning for cluster-track matching
Up: Calorimeter hit signal and
Previous: New formula for hadron
akiya miyamoto
2000-01-21