Transcript ppt

Steps toward understanding of ACD
First ACD data obtained in fully integrated LAT, with
the use of Tracker and Calorimeter data!
 Goal – complete the analysis of ACD Performance by SVAC workshop
02/28/2006. Results shall be used for settings in future ACD runs and for
LAT simulations
 I am discussing here the basic ACD Performance parameters:
•
MIP Peak position calibration and monitoring – calibration parameter
• Absolute Light Yield determination – goes to Monte Carlo model
• Tiles Light Collection Uniformity – goes to Monte Carlo model
• Pedestal positions – calibration parameter
• Ribbon Performance
Alex Moiseev IA meeting 01/27/2006
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MIP Peak Position Calibration:
• needed to set correct VETO thresholds to achieve required efficiency
• monitoring is needed to determine the health of ACD. We allow for 10%
variation
• Idea is to have MIP peak positions reference file. Now we use reference
file obtained at Goddard in July 2005, with ACD TrigOps test (ACD trigger)
• For future we need to create the reference file to be independent on the
particles flux angular dependence; use tracker to select “normal
incidence” muons. But we cannot do this for side tiles due to LAT trigger
geometry. Top tiles will be calibrated with LAT trigger, and side tiles – with
ACD trigger (how often during a flight?), with re-calibration to off-angle
events
• First try with B30 data – good data! Eric fitted mip peaks; now we need
to apply “normal incidence” cuts and to do fitting again
Alex Moiseev IA meeting 01/27/2006
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Absolute Light
Determination
• Need very clean muon sample
How clean is this? My cuts for tile
[Tile]:
AcdPha[Tile][0]>0
AcdRange[Tile][0]==0
AcdTkrIntSecTileId==Tile
9.99<AcdTkrIntSecPathLengthInTile<12 (or 11.9914 for thick tiles)
AcdActiveDist>25
Seems to be clean after these
cuts; Need to check with more
statistics
TkrNumTracks==1
Tkr1NumHits>30
VtxZ0>580
Tkr1Chisq<2
CalMipNum==1 (?) – reduces statistics significantly
•Light Yield is derived from tile detection efficiency measurement
Bill recommends to use variables from Merit to clean muon sample
Alex Moiseev IA meeting 01/27/2006
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Light Collection Uniformity
• Use track pointing
• Compare
with
“tomography”
measurements performed with every tile
at Goddard before ACD integration
• Not clear if it can be done for side tiles
•Results are very encouraging. We
predicted that light degrades from 100%
to 70% starting at 3 cm from tile edge;
Data shows better – 80-90% at 1-2 cm
Alex Moiseev IA meeting 01/27/2006
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Pedestal position
Problem:
• During all tests at Goddard, and in post-delivery test at SLAC all pedestals stay
within 2-3 ADc counts – what we want. Maximum pedestal shift we can allow
without re-calibration is around 5 ADC counts
• Some (10-15) channels have pedestals moved by up to 40 ADC counts for ADC
CPT – new GASU was used. Different voltage supplied to FREE?
• Tests B13 on January 13-14, 2006: 6 runs in total, and in the first run HV was not
turned ON – same as in ACD CPT Pedestal runs.
• Pedestal values between ACD CPT pedestal runs and that measured from PHA
histograms in first run (no HV) in B13 perfectly agree!
• There are some channels (6-8) with changed pedestals by 15-20 counts in B13
runs with HV ON. Does HV affect 3.3V voltage for FREE?
• Working on getting precise information about actual voltage values
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Ribbon Performance
• Ribbons are critical elements for ACD
efficiency because they seal gaps between
tiles
• Ribbons have strong light attenuation along
its length : ~3 p.e. in the PMT from muon
crossed ribbon in the center, and ~ 10 p.e.
from muon close to PMT. LAT model
simulations needs correct data
• Use of the tracker provide unique
opportunity to study light yield over ribbon
length. It was measured at Goddard twice,
but in both cases without precise pointing.
Now we will compare new results with that
obtained at Goddard
Light yield for Ribbon 602 along its
length on the top of ACD for both
PMTs.
Light yield measured in these tests
agrees very well with that measured at
Goddard for ALL ribbons – 3-4 p.e. in
the ribbon center. It is sufficient to
provide required ACD efficiency with
threshold set to 1-1.5 p.e. (40-60 ADC
counts)
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Direct measurement of Ribbon
efficiency
Approach – same as was done at Goddard.
Efficiency is measured directly for the area
shown by red. This area includes two adjacent
tiles with the gap cover by the ribbon. Tiles
have known light yield. Simulating this setup,
we vary light yield of the ribbon to match
experimental results
obtain ribbon
absolute light yield.
The main thing again is to find clean sample of
muons. Same approach as in slide 3. Works
OK, but need to use statistics from all 60 runs
of B30 – wait until re-processing is completed
Alex Moiseev IA meeting 01/27/2006
ribbon
Tile 1
Tile 2
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Conclusions
• We went through basic ACD performance parameters and found
that obtained data provides everything what we need to determine
them
• Several issues have been identified - pedestal move (Voltage
change?), events with veto in Gem but nothing in HitMap, some tests
in Long Functional have questions (not life threatening) – working on
them
• Waiting until Monday, when data is re-processed, to start detailed
analysis.
• Great appreciation of help from SLAC.
• ACD Ntuple variables (I used only SVAC Ntuples so far) are
excellent, did not find any mistake in them! Thanks a lot, Eric, Anders,
Heather, and all!
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