University of Iowa

1
University of Iowa
HF sourcing Histograming mode Alexi
Mestvirishvili
ECLIPSE 06 Antalya, Turkey
2
HF minus
Main calibration HTR
running in histograming mode, QIEs running in
normal scale. Reading out of one spigot at the
time (24 channels, 12EM, 12HAD) During sourcing
source was stopped in three different location
First and last for safety reasons. Second stop
for 3 minutes to accumulate data. Position of
second stop point was chosen in the way to have
both long and short fibers illuminated.
Expected signal ?0.01
SignalPedeatal
x10
QIE counts vs position
Ten 10o ? sectors 28 36 and 1 analyzed so far
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Signal pedestal and pedestal separation and
signal versus tower
Gaussian fit applied
EM fibers
HA fibers
Small peak pure pedestal High peak
Signalpedestal
? For these distributions are ?0.0018.
5 wedges 24 tower each
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Problems
Run 1566 1567 Tower 12, phi 36
Run 1490 Tower 23, phi 33
EM channels
HAD channels
Gaussian fit sigma for SP vs Tower
5
Problems (run 1566)
Red signal pedestal Green pedestal
Four different capacitors
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Calibration Precision

• Calibration precision is limited by several
  factor
• Statistical precision of signal
• (relative error on
  signal)
• 2. Pedestal stability
• 3. Internal nonlinearities of absorber and
  fibers
• (believed to be at the level 5, not
  studied for this presentation)
• 4. etc.

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Statistical PrecisionPhi29, tower16, QIE ch 2,8

• Signal pedestal
• Nentries 14290
• Mean 5.05
• Sigma 0.0018
• Err on Mean
• ?/sqrt(Nentries) 1.5x10-5
• b) Pedestal
• Nentries 3408
• Mean 5.039
• Sigma 0.0018
• Err on mean 3x10-5

a)
b)

• ? 5.05 5.039 0.011
• ?? 3.3x10-5

X axis units linearized QIE counts
??/?0.3
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Relative error on signal
Small towers has smaller signals hence big
error
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Pedestal stability
Pedestal stability can be studied from same
data. In one 10o 24 channels (12EM, 12HAD) are
read out during sourcing of one tube. Either 16
or 15 tubes are in one phi sector. In each run
only two channels (1EM, 1HAD) caries signal.
All other channels gives pure pedestal,
provided adjacent towers of one which is
sourced are excluded from data samples One can
easily select samples for the same channel and
well separated in time. App 5 minute is
necessary to source one tube. For example, two
samples for tower 5, when source is in tube 1
(tower 1) and in tube 16 (tower 12) are
separated by more than one 1 hour.
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Pedestal stability
Condition which has to be fulfilled to avoid
contribution From energy leakage from tower to
tower
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? of pedestal distributionstower 1 to 12
Smallest tower Is noisy as well
Tow 12,?36
12
? of pedestal distributiontowers 13 to 24
Small tower noisy as well
Tow 12,?36
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Geometrical corrections
Geometrical corrections has to be applied to
signals from each tower to exclude the
differences in tower shape. Coefficients were
taken from Monte Carlo. They are calculated
with respect to the response of infinite size
tower taken into account actual tower
geometry Coefficients are available in HF
monitoring database and they were calculated in
CMS IN 2004/002
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Geometrical correction how they work (problems ?)
for EM towers
Uncorrected, pedestal subtracted signal for phi
28
For towers having two source tubes geometrical
correction should bring two points close to each
other
for HAD towers
Gains in each group are more or less equal
High
Medium
Low
PMT gains
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Geometrical corrections how they work (problems)
Same as on previous slide
pedestal subtracted, Corrected, signal for phi
28
Points in red ovals move in opposite direction
Points in last group behaves as it should
High
Medium
Low
PMT gains
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SUMMARY

• In general, data quality is good, signal can be
  separated
• well even for small towers
• Statistical precision of HF calibration will be
  very high,
• less than 1.
• 3. Stable pedestal
• 4. Some problems were identified bad
  capacitors, noisy
• channels
• 5. Geometrical scale factors has to be
  recalculated with
• correct tower geometry (!!!!!!!!!)

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Backup slides
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Stability of pedestal Mean
RMS 0.00046
RMS 0.00034
RMS 0.00027
RMS 0.00034