Transcript Fermilab Test Beam Analysis - Florida Institute of Technology
Fermilab Test Beam analysis for CMS GE1/1-III GEM detector
Aiwu Zhang, V. Bhopatkar, M. Hohlmann, A. M. Phipps, J. Twigger Florida Institute of Technology 25/03/2014
Outline
• Motivation • Setup at Fermilab beam line • Data Analysis
Performances (gain, cluster size, etc.)
Detection efficiency
Tracking methods and resolution results
• Summary
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 2
Motivation of beam test
Performance study for large-area GEM detectors : Study a 1-m long trapezoidal GEM prototype (GE1/1-III) assembled at Florida Tech Study zigzag-strip readout designed by Fl. Tech (not the topic of this talk).
We conducted a beam test at Fermilab in Oct 2013 and collected more than 3 million raw events.
CMS GE1/1-III GEM detector: 1-m long, 22-45 cm trapezoidal detector.
CMS muon upgrade with GEM detector
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 3
Fermilab beam test configuration
CMS
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 4
Data taking & analysis
• Data were collected with AmoreSRS package through
SRU
system,
60 apv25 chips (7680 channels)
were read out simultaneously. • Data are also analyzed using AmoreSRS; cluster information was output into text files for further tracking analysis.
• The entire CMS GE1/1 GEM detector needs 24 APVs, but
we mounted 8 APVs (one APV on one eta sector) at one time
and measured three different groups.
Upper APV Middle APV position Lower APV Sector 8 Sector 1 Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 5
Beam profiles
We have measurements with pure 120GeV proton beam, and mixed hadron beam (energy points 20GeV, 25GeV, 32GeV).
Mixed hadron beam had an elliptical spot, ~6cm by 2cm size; pure proton beam spot was much narrower – a 1-2cm diameter circle.
Most of our raw data were taken with 32GeV mixed hadron beam
.
Mixed hadron beam (32GeV) 120GeV proton beam Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 6
Basic Characteristics of the GE1/1-III GEM detector
1. Cluster charge (in ADC counts) 2. Cluster size (number of strips)
HV 3250V, APV in Middle sector 5 @32GeV beam Distribution fits well to a Landau function, MPV is 305 Mean cluster size vs. HV “gain” curve on sector 5: MPV value of above distribution vs. high voltage Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 7
Basic characteristics of the GE1/1 III GEM detector (cont’d)
3. Gain uniformity: variation of mpv. cluster charge vs. eta sector Time bin of max. signal amplitude.
(3250V, Eta5) 4. Time bin characteristic: The DAQ was configured to record pulses over 9 time bins (25ns/bin) Mean Time bin vs. HV (Eta5)
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 8
Detector efficiency
Efficiencies at 3,4,5,6 sigma (ped. width) cuts on strip charge Efficiencies with the same cut as applied to VFAT (Note: 10 VFAT units ~ 5 sigma) Detector efficiency was measured in middle eta-sector 5 in 32GeV beam.
Different hit thresholds were applied to strip charges (N-sigma cut on pedestal width, N=3,4,5,6).
Efficiency vs. HV fits well to a sigmoid function.
Plateau efficiency ~ 97.8% (with 5 sigma cut).
With the same threshold as for VFAT(10,12,15), plateau efficiency is 97% Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 9
Tracking: Alignment of trackers
Tracking was done first for reference detectors to make sure that trackers were working properly. Also we found resolutions of the trackers in the process.
Only single-cluster events for each tracker were selected for tracking.
Our alignment method (two steps): First Then
shift
the center of the detectors to the beam center
perform rotation
s in (X,Y) plane for the back three trackers, in order to put them in the same orientation as the first tracker.
Example: Shift in X for the first tracker
beam
120GeV
First_X
3.6876
First_Y
1.852
Second_X
-1.77
Second_Y
-2.43
Shift was performed by iterating: (1) Look at residual distributions for straight-line fits on each X and Y plane, fit them with a double-Gaussian function and take the mean values (2) Shift positions by 20% of the mean
Third_X
-8.41
values of the residuals (3) Repeat these steps until all mean residuals for the 4 trackers are less than 10 μm
Third_Y
15.76
Fourth_X
-17.53
Fourth_Y
-0.87
Shift par.
unit: mm 32GeV 10.72
1.018
6.289
-3.296
-1.418
14.95
-10.46
-1.443
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 10
Tracking: Alignment of trackers – rotations
Rotation of other three detectors relative to the first tracker.
• Consider only rotation in XY plane (around Z axis). If detectors are fully aligned, the two coordinate systems have the same origin in XY plane.
• An initial approximate rotation angle α could be calculated as most tracks are close to normal onto the detectors. • In the formula on the right, (x,y) are measured by 1 st ref detector, ( x’,y’) by the other detector (e.g. REF3).
In 1 st ref. system sin( α) = (x’y – xy’)/(x^2 + y^2) Rotated angles after shift (these are the starting points for final optimization):
2 nd ref.
9.5mrad
3 rd ref.
-4.7mrad
4 th ref.
-24.7mrad
Dist. of angle between 2 nd and 1 st ref. det.
• Once the angles are known, the positions in each detector can be corrected.
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 11
Tracking: Alignment of trackers – rotation results
Example: Avg. rotation angle for 2 nd –1 st :
3.9 mrad
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Tracking: Alignment of trackers – rotation results
Rotation angle for 3 rd -1 st :
-17.35mrad
(avg.) Rotation angle for 4 th -1 st :
-48.5mrad
(avg.) Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 13
1 st ref.
σ=36μm
3 rd ref.
σ=42μm
In
clusive residuals in
X
for trackers
2 nd ref.
σ=54μm Double Gaussian Fits
4 th ref.
σ=41μm Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 14
σ=27μm
In
clusive residuals in
Y
for trackers
σ=43μm σ=44μm σ=40μm Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 15
σ=134μm
Ex
clusive residuals in
X
for trackers
σ=77μm σ=88μm σ=91μm Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 16
σ=99μm
Ex
clusive residuals in
Y
for trackers
σ=62μm σ=73μm σ=92μm Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 17
Final resolutions for trackers
1 st _X 2 nd _X 3 rd _X 4 th _X 1 st _Y 2 nd _Y 3 rd _Y 4 th _Y Residual width (ex.) 134 77 88 91 99 62 73 92 error 1.9
1.1
1.1
1.5
1.5
1 1.1
1.2
Residual width (in) 36 54 42 41 27 43 44 40 error 0.5
0.7
0.9
0.7
0.4
0.7
0.7
0.5
Resolution ( μm) 69 64 61 61 52 52 57 61 error 1.4
1.2
1.5
1.4
1.1
1.2
1.2
1.1
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Transfer to polar coordinates
Origin / vertex ~9.94
°
CMS Eta5 REF Det.
X X offset CMS GEM detector has a trapezoidal shape with radial strips and measures ϕ.
We have measured its opening angle to be 9.94
° directly from the pcb; the angle pitch between neighboring strips is a constant (0.453mrad). This angle is not exactly 10 °; need to review r/o board design for the number (also need to be known and verified for next prototypes and final design).
It is most natural to study the CMS spatial resolution in azimuthal direction ( ϕ) instead of in Cartesian coordinates (x, y). What we need to do is to choose the vertex (of CMS GEM) as the origin of the tracker system .
We did not measure the distance between vertex and beam center (it is also hard to measure), so we need to figure out the X and Y offsets for trackers from data in order to make the tracker origin match the CMS GEM detector vertex .
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 19
Tracker Inclusive residuals in “r”
σ=46μm σ=69μm σ=55μm σ=59μm Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 20
Tracker Inclusive residuals in “ϕ”
σ=21μrad σ=31μrad σ=23μrad σ=25μrad Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 21
Resolutions in polar coordinates
REF2_r REF3_r UVA3_r REF1_r REF2_ ϕ REF3_ ϕ UVA3_ ϕ REF1_ ϕ exclu. width 166 98 89 137 75 44 38 56 Error 0.9
0.4
0.4
0.5
0.3
0.2
0.1
0.2
inclu. width 46 69 55 59 21 31 23 25 Error 0.2
0.3
0.2
0.2
0.1
0.2
0.1
0.1
Resolution (geom. mean) 80 82 70 90 39 37 30 38 Error 0.4
0.5
0.4
0.5
0.2
0.2
0.2
0.2
Unit μm μrad Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 22
Comparison of tracker resolutions in Cartesian and polar coordinates
REF2
σ ϕ [μrad]
3.6
46 4.2
21
REF3 UVA3 -3.6
-11.6
69 55 -5.7
-3.6
31 23
-3.6
-11.6
σ x [ μm] 46
σ y [ μm] 45 66
55 -8
49
REF1 10 59 5
25
10 59 10 55
53
• • Resolutions in (x,y) are also calculated at this origin.
• Resolutions in r are very close to resolutions in X.
The last column shows the calculated resolutions in y from resolutions in ϕ, they match with the measured resolutions in y
.
• Also,
• Tracking in polar coordinates works well and gives high resolutions.
σ y σ ϕ L Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 23
Resolution study for CMS GE1/1-III GEM detector
vertex ~9.94
°
CMS Eta5 REF Det.
X X offset Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 24
X and Y offsets optimization
Track 2 in ϕ versus X @
Y=-30mm
Track 2 in ϕ versus X @
Y=-28mm
Look at track χ 2 in ϕ in versus X offset,
only between Y at -28mm and -30mm, it shows a parabolic curve
. (Y beyond that range gives bad curves) Y=-29mm is taken as the optimized offset; we fit this curve, then we get Track 2 in ϕ versus X optimized X offset at -1864mm . @
Y=-29mm
Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 25
Double check Y offset and global rotation parameter
Track Χ 2 in ϕ versus Y @
X=-1864mm
Minimum point gives Y=-29.1mm Double check Y offset, -29.1mm
Consistent with -29mm on last slide.
Rotation angle
is near zero (28 μrad) Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 26
Resolutions for CMS GEM detector at eta sector 5
Inclusive residual σ= 86μrad Exclusive residual σ= 111μrad
Excl. residual from VFAT test beam in 2012 P. Barria • Inclusive (exclusive) residual widths are 86 (111) μrad or 160 (207) μm • Again form the geometric mean:
Resolution is 98 μrad or 182 μm
.
• This resolution is considerably better than the VFAT resolution (276 μm) as expected for electronics that measures charge-sharing well Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 27
Resolution versus HV
Repeat same analysis for data sets taken with different HV applied to CMS GE1/1-III during HV scan.
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Comparison of resolution and detection efficiency
resolution •
Compare the resolution and efficiency vs. HV
•
The best spatial resolution is obtained when the detector is operated on the efficiency plateau (as expected)
efficiency Aiwu Zhang et al., FNAL Test Beam Analysis / CMS GEM Workshop VIII, March 2014 29
Summary and outlook
• The beam test at Fermilab was successful; the CMS GE1/1-III GEM detector and the tracking detectors performed very well.
• GE1/1 GEM was stable with high detection efficiency (97.8%).
• The response uniformity for eta sectors 7 and 8 were somewhat worse. This could be due to uneven gaps when stretching the foils.
• Spatial resolution analysis in Cartesian and polar coordinates is working properly.
• Current best measurement for spatial resolution for eta sector 5 is 98 μrad or 182μm (at 3250V). Spatial resolution improves with increasing HV until plateau is reached.
Future work: • Measure resolutions for other sectors of the GEM detector and position dependence (as fct. of r and ) • Do tracking with simulated VFAT clusters.
• Study and correct for non-linear response of strips.
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