¥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:
¥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)
¥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)
¥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)
¥Described
algorithm works in online and offline data processing for years. Now we should
try to implement something like that into Level1 trigger
electronics.