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For cluster reconstruction purposes EC
can be considered as 3 planes called U, V and W, crossing each other at 120
degrees (see figure 1). Each plane has 36 strips, each strip equipped with
PMT to be connected to individual Flash ADC channel. EC cluster finding
procedure includes following steps: |
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Step 1: threshold[0] applied to the
energies from individual strips; only strips with energies above threshold[0]
reported to the following step in a form of STRIP(strip number, strip energy) |
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Step 2: each plane is scanned searching
for 1-dim peaks, defined as Ôgroup of one or several neighbor strips with
energy above threshold[0] separated from another groups by at least one strip
with energy below threshold[0]Õ (see figure 2). Energy sum and weighted
coordinate are calculated for every peak, and peaks with energy above
threshold[1] are reported to the following step in a form of PEAK(peak
ÔcenterÕ strip number, peak energy) |
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Step 3: 1-dim peaks from each of three
planes are processed using following simple formula:
(37-delta)<=(U+V+W)<=(37+delta) (see figure 3). If three peaks from 3
planes satisfies to that formula they considered as parts of one 2-dim
cluster. Energy sum and weighted coordinate are calculated for every 2-dim
cluster, and clusters with energy above threshold[2] are reported as final
result in a form of CLUSTER(three cluster ÔcenterÕ strip numbers, cluster
energy) |
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Described algorithm works in online and
offline data processing for years. Now we should try to implement something
like that into Level1 trigger electronics. |