Particle incident angle study with Mimosa 17
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![Page 1: Particle incident angle study with Mimosa 17](https://reader035.fdocuments.us/reader035/viewer/2022062517/56812c86550346895d913912/html5/thumbnails/1.jpg)
Particle incident angle study with Mimosa 17
C.Dritsa, J.Baudot
Outline• Motivation• Digitiser• Analysis• Summary
11th CBM collaboration meeting GSI Darmstadt
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Motivation
Open charm feasibility studies are of major importance for CBMThe MVD is the key detector for open charm measurements.
Background & Signal Generation
Transport
(GEANT)
Simulate detector’s response
For MVD:gaussian smearing
The actual model using gaussian smearing is not adapted for studying event pile-up and delta electrons.
Can this model be improved ?
The implementation of a more realistic MAPS response ( digitisation model ) will allow us studying the impact of the above points especially on the open charm reconstruction. This work is under progress at IPHC, Strasbourg.
Geometry (thickness, stations’ position)
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Simplistic illustration of the digitisation model
Digitisation model for non depleted detector (MAPS detector):
1. Particle trajectory divided in segments inside the sensitive volume.2. Energy deposited in each segment is translated into charge.3. Charge spread in the sensitive volume within a defined cone.
No Electric Field:
Electrons are diffusing sensitive volume
θ
Advantage of digitiser: possibility to study particles with inclined tracks.Need to adapt the model’s parameters in order to reproduce experimental data.
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Beam Test
•Beam test performed in November 2007 at CERN with a 120 GeV pion beam.
•The chip under test was a MIMOSA 17 :30 μm pitch - 14μm epi
MIMOSA 17
MAPS response to tracks with large incident angle was not studied in detail yet.
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• The two external planes (reference planes) are used for track reconstruction.• The middle plane is the Detector Under Test (DUT): the tracks extrapolated in the DUT are matched with the hit located closest to the reconstructed track position.• Measurements were taken for several angles:• θ: 0°, 15°, 30°, 45°, 60°, 75° and 80°
Analysis steps
Top view of the setup
Reference plane:MIMOSA 17
Reference plane:MIMOSA 17
DUT
θ: 080!
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Charge collected
in each pixel
PitchSize
tN pix
tan
How is the cluster shape affected when track is inclined ?
L
,PitchSizeNU pix
Lt
L: length of the particle trajectory in the epitaxial layert: epitaxial layer thicknessθ: angle of incidence with respect to the vertical
cos
80 tQ tot
tantU
cos
tL ,)/(80 LmeQ tot
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• 7x7 cluster
• Each square represents one pixel
•Color scale normalised
Average Cluster Shape
Q on seed (MPV, e-)
250
249
285
348
506
823
964
Angle (°)
0
15
30
45
60
75
80
0° 15° 30°
45° 60° 75°
80°
Differences in the average cluster shape are obvious for large angles (>60o)
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0° 15° 30°
45° 60° 80°
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Cha
rge
colle
cted
(el
ectr
ons)
Collected charge
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Signal to Noise Ratio on seed
• For small angles (<30o) the SNR is almost constant
• For bigger angles (>60o) the SNR varies significantly
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Residuals
U
Vσ of the distribution of track-hit distance.
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Can the inclination of the track be derived from cluster properties?
The number of significant pixels (above given threshold) is higher for 80° than for 0°.The aspect ratio is different.
Allow to identify and suppress hits from delta electrons?
U
V 0° 80°
Comparison of properties of average clusters for two angles:
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....
...)3()2()1(
3,32,21,1
23,3
22,2
21,1
2
uvuvuv
uvuvuv
QQQ
vQvQvQ
Q
VQWidth defined by :
- 0°- 80°
V cluster width
U c
lust
er
wid
th
V cluster width
Can the inclination of the track be derived from cluster properties?
80°v=
u
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Beam test (pions, 120GeV) on inclined tracks up to 80° was performed.
For small angles (<30o) the SNR of the seed, the charge of the seed and the charge of the full cluster are constant.
For large angles (>60o) the SNR of the seed , the charge of the seed and the charge of the full cluster increase significantly.
The residuals along the V direction (along the rotation axis) remain constant but the residuals along the U direction increase (up to 4 times for 80 degrees, but algorithm not optimised)
It seems possible to identify hits created from tracks with large incident angle. Investigate possible applications of this identification.
Next steps:Implementation of the digitiserPerform simulation study to evaluate the fraction of particles with large incident angle.
Summary and results
MotivationImplement MAPS digitiser.Study MAPS response to inclined tracks.
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1 1
1 1 1 1
1 1 1
Can the inclination of the track using information from the cluster be derived ?
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Q(Vi,Ui) Q(1,1)
Q(0,0)
Q(-1,1)
....
...)1()1()0(
1,11,10,0
21,1
21,1
20,0
2
QQQ
QQQ
Q
VQ
U
V
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1 Digital3 CoG 3x35 CoG 5x57 Eta 4var9 Eta 3x311 Eta 2x213 Eta 5x5
0 degrees 80 degrees
Residuals 7x7 cluster: Different methods
The residuals obtained from eta 3x3 are the best even for 80 degrees rotation
Res
idu
als
(μm
)
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Charge on Seed
250 249 285348
506
823
964
0
200
400
600
800
1000
1200
0 10 20 30 40 50 60 70 80 90
rotation anlge (degrees)
elec
tro
ns
Charge on seedMIMOSA 17 ( 14microns epi )
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Charge 49 pixelsMIMOSA 17 ( 14microns epi )
Charge on 49 pixels
886 895 10051258
1847
3755
5048
0
1000
2000
3000
4000
5000
6000
0 10 20 30 40 50 60 70 80 90
rotation angle
char
ge
on
49
pix
els
(e-)
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Noise on seed
14,8 14,8
14,7
14,8
15
14,9
14,5
14,4
14,5
14,6
14,7
14,8
14,9
15
15,1
0 10 20 30 40 50 60 70 80 90
rotation angle (degrees)
elec
trons
Noise on seedMIMOSA 17 ( 14microns epi )
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Charge on 49 pixels
886 895 10051258
1847
3755
5048
0
1000
2000
3000
4000
5000
6000
0 10 20 30 40 50 60 70 80 90
rotation angle
char
ge
on
49
pix
els
(e-)
cos
80 tQ tot
constQtot cos
if CCE is const and clustering is correct:
Qtot*cos(theta)
750
800
850
900
950
1000
-20 0 20 40 60 80 100
angle (degrees)
Q(4
9pix
els)
*co
s(th
eta)
~10%
Error bars correspond to 1o
error in defining the rotation
angle
With a 10% precision CCE can be approximated as constant wrt the particle incident angle
What about charge collection efficiency at large angles?
Charge on 49 pixels (Qtot)
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0 degrees 80 degrees
Residuals 7x7 cluster
μm μm
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0 15 30
45 60 75
80
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SNR on seed (MPV in e-)
250
249
285
348
506
823
964
Angle (degrees)
0
15
30
45
60
75
80
0 15 30
45 60 75
80
• 7x7 cluster
• Each square represents one pixel
•Color scale normalised
Mean Cluster Form (3D)