ACD tile events with only one adc
above zero-suppress threshold
Larry Wai
Oct. 21, 2005
Run info
• I&T ACD Triggered Op run 134001103,
first 100k events
• Coincidence regions are top-side (x4),
opposite sides (x2), adjacent sides (x2)
• Zero suppress threshold set at 15 adc
counts above pedestal mean
Example ADC distribution
• Tile 44, adc0; same
as GARC 8 ch7
• Pedestal mean =
230.9
• Pedestal RMS = 3.4
• Zero suppress =
mean + 15 = 246
• Black line is for all
events
• Red line is for adc1=0
Typical event
• Evt # 25
• 4 tiles hit
• all tiles had both
ADCs above zero
suppress threshold
Another typical event
• Evt # 137
• 2 tiles hit
• No tiles w/ single adc
hit
“CNO” event
•
•
•
•
Evt # 158
11 tiles hit
Non-zero CNO vector
1 tile w/ single adc hit
(probably noise hit,
i.e. zero suppress
threshold too low)
“Small” event w/ large fraction of
single adc hit tiles
• Evt # 359
• 4 tiles, one ribbon
• 3 tiles w/ one adc hit
Another “small” event w/ large
fraction of single adc hit tiles
• Event # 562
• 4 tiles hit
• 3 tiles w/ single adc
“big event”
• Evt # 337442
• 74 tiles hit
• 7 tiles w/ single adc
hit
“large” event dominated by single
adc hit tiles
• Evt # 785
• 55 tiles hit
• 38 tiles w/ single adc
Another “large” event with many
single adc hit tiles
• Evt # 3462
• 20 tiles hit
• 15 tiles w/ single adc
hit
Events w/ large numbers of single
adc hit tiles
One entry per event
•
Top left: number of tiles w/ both adcs above
threshold versus total number of tiles
•
Top right: number of tiles w/ only one adc
above threshold
•
Bottom left: black is distribution of RoiVector
coincidences (8 bit word, lowest bit is
coincidence of lowest RoiVector pair, highest
bit is coincidence of highest RoiVector pair,
etc.), red is fraction of events with more than
half the tiles with only one adc above
threshold
•
Bottom right: fraction of events with both
adcs above threshold (the yellow shows the
event selection for the bottom left red
histogram)
Review
•
•
Typical events have zero or at most a
few tiles w/ one adc hit
For events with >10 tiles hit, two classes
of events emerge:
1. Events with a few tiles w/ one adc hit, i.e.
the “big event” shown
2. Events with most tiles w/ one adc hit, i.e. the
other 2 large events shown
Question of the day
• Are the events w/ >10 tiles and mostly w/
one adc hit real physics events or bursts of
noise?
• Check this by looking at ACD triggered
events w/ TKR; i.e. for bursts of noise, we
should see no hits in the TKR, whereas for
“real” large events we should see lots of
hits in the TKR