Transcript ppt

Gamma-ray Large Area Space
Telescope
Study of the ToT on the
full LAT data sample:
corrections & updates
F. Loparco
INFN Bari
1
What was wrong?
• IA Workshop 6:
• discrepancies between results in full LAT configuration and
previous results
• We did not take the ACD into account! (thanks Anders!)
• Analysis cut correction:
• muons are tagged by GemConditionWord=3 instead of
GemConditionWord=2
2
List of the runs analyzed
A data samples of 20 runs has been analyzed:
135005345, 135005347, 135005349, 135005351, 135005355,
135005357, 135005359, 135005363, 135005365, 135005367,
135005371, 135005373, 135005375, 135005377, 135005379,
135005381, 135005383, 135005385, 135005387, 135005389
These runs have been performed on Jan 14-15, 2006 in the
B2 configuration
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Event selection & definitions
Event Selection:
Trigger from 3 consecutive layers: GemConditionWord=2
= 3!!!!
Single tower events: GemTkrVector[tower] ≠ 0 for only one tower
Single muon tracks in the TKR: TkrNumTracks=1
Triggering Layers = Layers in both views from GltLayer (First Triggering Layer)
to GltLayer+2 (Last Triggering Layer)
Track Layers = Layers in both views from Tkr1FirstLayer (First layer in the
track) to Tkr1LastLayer (Last layer in the track)
0
left ToT

ToT  
right ToT

left and right ToTs
if both left and right ToT  0 or NA
if right ToT  0 or NA
if left ToT  0 or NA
if both left and right ToTs  0
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cosθ distributions
In central bays tracks with large zenith angles are ruled out
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Azimuth angle φ distributions
Symmetries reflect the TKR geometry!
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ToT distributions for triggering layers
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Evaluation of the hit capture efficiency
1 - ε  f(ToT  0)
With the exception of bay 0, for all towers 1-ε < 0.1%
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ToT vs track parameters
Z
Track length
l  1/cos



X
Projected
track length
Y
 l cos 2   sin 2  cos 2  , for X layers

l'  
2
2
2

l
cos


sin

sin
 , for Y layers

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ToT vs zenith angle
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ToT vs zenith angle: linear fit results
The previous histograms have
been fitted with a linear function:
ToT  a  b/cos 
• Fit results slightly changed with
respect to the ones shown at the
IA workshop 6
• As expected, the fit results are
similar for all integrated towers
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ToT vs l/l’
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ToT vs l/l’: linear fit results
The previous histograms have
been fitted with a linear function:
ToT  a  b(l/l )
• Fit results changed with respect
to IA workshop 6
• a small; b  40  ToT is almost
proportional to the ratio l/l’
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Are results compatible with previous ones? Yes, now they are!
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Conclusions
• The ToT dependence on the track parameters has
been investigated
• The analysis cuts have been corrected
• Symmetries in the angular distributions of muon
tracks can be explained taking the geometry into
account
• Results in the full LAT configuration are compatible
with previous analysis
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