glast calorimeter crystal position measurement zach fewtrell, nrl/praxis glast integration &...
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![Page 1: GLAST Calorimeter Crystal Position Measurement Zach Fewtrell, NRL/Praxis GLAST Integration & Test Workshop SLAC July 14, 2005](https://reader035.vdocument.in/reader035/viewer/2022062805/5697bffc1a28abf838cc1ae1/html5/thumbnails/1.jpg)
GLAST Calorimeter Crystal Position Measurement
Zach Fewtrell, NRL/PraxisGLAST Integration & Test Workshop
SLACJuly 14, 2005
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Data Set
4 TOWER DATA, ZERO SUPPRESSED
~600K events
~3K hits per cal xtal.
-All values extracted from SVAC tuple files.
- Runs 135002769 - 135002780
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Software Environment
TRACK EXTRAPOLATION & CUSTOM TUPLE GENERATION
- Compiled C++ using ROOT libraries.
- Based on David Smith's/Benoit Lott's anaMeritNtuple.C
- More inclusive of partial xtal hits.
TUPLE ANALYSIS & PLOT GENERATION
- ROOT interactive.
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Plan of action
1 – Retrieve main Tracker track position & vector at end
of track.
2 – Using LAT & Cal geometry constants, extrapolate
track into the Z-center of each Cal layer.
3 – extract cal xtal hit info for appropriate crystal.
4 – calculate longitudinal component of tkrPos – calPos.
5 – ‘diff’ is the main variable I study.
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Initial cuts1 – TkrNTracks > 1
2 – Track can cut tower boundary, i skip layers where track crosses the
boundary.
3 – Partial hits allowed, but I only measured the hits which contain the
middle of the track.
- in any given layer, this should be the strongest hit.
- mostly driven by lack of desire to write more code, plenty of
partial track-hits already included.
4 – cal has to have a readout (ene > 0) duh!
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Step 1: Xtal Ends
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- Tracker extrapolated pos -vs- Cal Recon xtal pos
- scatter plot of all xtal hits..
- Cal clips xtal pos to CsI length, you don’t see the matching tails. This
adds bias to cal recon pos near xtal end.
-- NOTE: This effect is probably less w/ high energy showers.
- FIRST CUT: tkrPos > 23-28mm from xtal end
- SECOND CUT: calPos > 3mm from xtal end
Step 1: Xtal Ends
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Step 2: CalTkr Diff –vs- energy
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Step 2: Diff –vs- ene sigmas
X
XX
Error from pedestal noise.(back-of-envelope)
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Step 2: Diff –vs- ene
1 – Position sigmas at low energies < 10 MeV per xtal
consistent w/ propagated pedestal sigmas.
2 – plots from now on are cut at xtal ene > 7 MeV.
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All Crystals: Diff -vs- xtal index
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Distribution of single channel mean difference
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Distribution of single channel sigmas- consistent w/ other studies.
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Distribution of reduced 2
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Worst case channel T4 L7 X10
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Best Case T1 L3 X10
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Typical Channel – T0 L1 X10