Transcript (ppt)
Outline
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Analysis of some real data taken with the GLAST
minitower (cosmic rays only).
Offline analysis software used.
Full Monte Carlo simulation using GLEAM with the
minitower geometry.
Angular distributions
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Red dotted line is the
geometrical upper limit on
theta (~82 degrees), given the
minitower aspect ratio.
Black histograms: data.
Blue crosses: Monte Carlo.
Red
line:
expected
distribution (CR flux +
detector angular response).
TOT vs. theta
Average of TOT distribution increases as theta increases (the
bigger the angle, the longer the path in the silicon).
Real data
Monte Carlo simulation
TOT vs. theta projected on XZ-YZ
Example of average TOT as a function of the polar angle theta projected on the XZ
or YZ plane (real data). Distributions are shown for the X3 layer (i.e. strips oriented
along Y axis!).
Along the Y axis: the bigger the angle,
the bigger the charge released on a
single strip.
Along the X axis: more complicate
interplay between path length in the
silicon and charge sharing.
TOT vs. phi
Average TOT as a function of the azimuthal angle (real data) is
clearly oscillating:
• Tracks along the strips direction: big TOT.
• Tracks orthogonal to the strips: charge sharing.
Note the 90 degrees phase difference between layers X3 and Y3.
TOT vs. hit multiplicity
Average TOT as a function of the hits multiplicity (number of fired
hits per event) shows a minimum @ 2 (charge sharing on almost
vertical tracks) confirmed by Monte Carlo simulation.
Real data
Monte Carlo simulation
Hitmaps
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Black histogram: data.
Blue crosses: Monte Carlo simulation.
Red line: expected distribution for a “perfect” detector (not including the
shadow effect of not active regions on ladder edges, which are very well
reproduced by the Monte Carlo simulation).
Hitmaps
~ 200 strips not
wire bonded.