Performance of Drift Chambers for E906/SeaQuest Drell–Yan

Performance of Drift Chambers
for E906/SeaQuest Drell–Yan Experiment
at Fermilab
Kei Nagai
for SeaQuest Collaboration
Tokyo Institute of Technology
APS/JPS Joint Meeting @ Hawaii
11th Oct., 2014
Contents
1. Introduction
2. SeaQuest Spectrometer
3. Position Resolution of Drift Chambers
4. Single Plane Efficiency of Drift Chambers
5. Summary
SeaQuest
Kei Nagai
1
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1. Introduction
SeaQuest studies the structure of the proton.
-
the flavor asymmetry of anti-quarks in the proton.
120 GeV proton beam at Fermilab is used.
¯ u in the region 0.1< x <0.45 by Drell–Yan process
We will measure d/¯
... x: Bjorken x
We detect muons from Drell–Yan process.
-
momentum ~ 40 GeV
Hadron
q
q¯
Hadron
SeaQuest
+
µ
µ
Kei Nagai
Drell–Yan Process
q q¯
µ+ µ
2
Accelerator
Run2 data taking
Run3 data taking
Shutdown
Nov.
Sep.
Oct.
2013
2014
2014
•
Toward Run3, performance of drift chambers has been
investigated with Run2 data.
•
I will report on
•
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position resolution of drift chambers and
single plane efficiency of drift chambers.
The data were taken with 1
-
SeaQuest
10
12
The intensity will increase to 2
Kei Nagai
protons/s intensity beam.
1012 protons/s.
3
2. SeaQuest Spectrometer
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Target: proton,
deuteron, carbon,
iron, and tungsten
•
Magnet:
momentum
determination of the
muons
•
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There are four tracking stations for detecting muons; Station 1, 2, 3, and 4.
St. 3 consists of two parts;
‣ St. 3+: upper half of St. 3
‣ St. 3- : lower half of St. 3
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Each of St. 1, 2, 3+, and 3- consists of a drift chamber and a hodoscope.
St. 4 consists of proportional tubes and a hodoscope.
SeaQuest
Kei Nagai
4
Chamber Plane Configuration
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Each drift chamber has
six planes; X, X’,V, V’, U,
and U’.
X and X’ planes are vertical.
V and V’ planes are tilted by +14º from vertical direction.
U and U’ planes are tilted by -14º from vertical direction.
Detector
St. 1 Drift Chamber
St. 2 Drift Chamber
St. 3+ Drift Chamber
St. 3- Drift Chamber
SeaQuest
Plane
Plane
Cell
Maximum
Detector
Name Width (cm) Height (cm) Width (mm) Drift Time (ns)
D1
D2
D3p
D3m
102
231
222
222
122
269
160
160
Kei Nagai
6.4
20.8
20.0
20.0
110
280
270
210
5
D3p
D3m
KMag
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We use 18 planes in total for tracking.
In order to investigate chamber
performance, “global tracks” are used.
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•
FMag
Target
“global track” : track reconstructed with
all the chamber planes
D1
D2
global
track
Magnet
Goal of position resolution is calculated based on goal of mass resolution of µ+ and µ-.
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mass resolution < 0.24 GeV (contribution of multiple scattering is dominant)
position resolution < 400 µm
Goal of single plane efficiency is calculated based on tracking efficiency.
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single plane efficiency > 95%
tracking efficiency will be 90% with this single plane efficiency.
‣ assume a global track needs 5 or 6 hits per chamber
SeaQuest
Kei Nagai
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3. Position Resolution of Drift Chamber
Definition :
Position resolution = the standard deviation of the residual at the plane
Wire
Reconstructed
Track
Residual
Chamber Plane
•
Drift Distance
Track quality cuts are applied.
Number of hits associated with track = 18
2
Reduced of track < 3.0
Goal of resolution < 400 µm
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SeaQuest
Kei Nagai
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D1
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D2
Position resolution vs Drift time of each drift chamber.
Smooth curves have been obtained.
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there is no very high or low point
a constant value is used in analysis
SeaQuest
Kei Nagai
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D3p
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•
D3m
Position resolution vs Drift time of each drift chamber.
Smooth curves have been obtained.
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there is no very high or low point
a constant value is used in analysis
SeaQuest
Kei Nagai
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Summary of Position Resolution
Plane Name
D1U
D1U’
D1X
D1X’
D1V
D1V’
D2V
D2V’
D2X’
D2X
D2U
D2U’
Goal
400 µm
400 µm
Result
260 µm
240 µm
370 µm
350 µm
220 µm
220 µm
370 µm
320 µm
380 µm
370 µm
390 µm
390 µm
Plane Name
D3pV’
D3pV
D3pX’
D3pX
D3pU’
D3pU
D3mV’
D3mV
D3mX’
D3mX
D3mU’
D3mU
Goal
400 µm
400 µm
Result
370 µm
380 µm
320 µm
330 µm
320 µm
340 µm
330 µm
340 µm
420 µm
470 µm
320 µm
410 µm
• The position resolutions shown here are average values of the planes.
• Position resolution at each plane of D1, D2 and D3p is better than goal.
• Some planes on D3m are worse than goal but are tolerable.
SeaQuest
Kei Nagai
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4. Single Plane Efficiency of Drift Chamber
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Definition of single plane efficiency (of D1X, for example)
‣ Track must have a hit on all planes except D1X
‣ Efficient
track: track which does
have a hit on D1X
In-efficient track: track which does not have a hit on D1X
‣ Efficiency of D1X
Number of efficient tracks
Number of efficient and in-efficient tracks
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Efficiency of other planes is obtained by the same method.
Goal of efficiency > 95%
SeaQuest
Kei Nagai
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Efficiency
Effciency
1.04
D2
D1
1.02
D3p
D3m
maximum (100%)
1
0.98
0.96
Goal (95%)
0.94
0.92
90%
0.9
D3mV’
D3mV
D3mX’
D3mX
D3mU’
D3mU
D3pU
D3pU’
D3pX
D3pX’
D3pV
D3pV’
D2U’
D2U
D2X
D2X’
D2V’
D2V
D1V’
D1V
D1X’
D1X
D1U
0.86
D1U’
Stat. errors are smaller than points.
0.88
of each plane of D1
• Efficiency
and D3m is better than goal.
Planes
• Efficiency of each plane of D3p is lower than goal.
- HV was set lower to suppress rather-high leak current.
- D3p >90%, the others >95% → the effect of in-efficiency of D3p is small.
- We are optimizing the D3p now toward Run3.
‣ Attach aluminum Mylar to D3p in order to avoid humidity going into the
chamber.
SeaQuest
Kei Nagai
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There are some remaining problems on the efficiency.
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The figure on the left shows
local efficiency of D1U’.
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Horizontal axis: Wire position
Vertical
axis: Efficiency
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Efficiency is highest at the center
of the plane.
What causes such a phenomenon?
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Wire hit rate dependence or performance of tracking might be the
reason.
I’m investigating that now.
SeaQuest
Kei Nagai
13
5. Summary
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SeaQuest studies the structure of the proton, especially studies the flavor
asymmetry of anti-quarks in the proton.
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SeaQuest spectrometer has four tracking stations for detecting muons; Station 1,
2, 3, and 4.
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Station 1, 2, and 3 have drift chamber(s).
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The position resolution of each plane of drift chambers is better than goal (400
µm) except three planes of D3m, but they are tolerable.
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The single plane efficiency of each plane of D1 and D3m is larger than goal (95%).
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Efficiencies of two planes of D2 and all the planes of D3p are less than goal, but
the effect is not very large because the efficiencies of the other planes are high.
There are some remaining problems on efficiency to be studied.
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SeaQuest
Effect of wire hit rate and effect of performance of tracking on the single plane
efficiency will be investigated.
Kei Nagai
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Backup
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Backup: humidity and leak current
leak current
humidity
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Backup: St. 3 chambers
D3p
• Clear mylar is attached.
- useful when wire repairing
D3m
• aluminized mylar
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Backup: multiplicity dependence
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Noise hit removal is applied for tracking.
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It would remove true hit accidentally.
→ efficiency drops happen more at higher multiplicity region.
Investigation of the behavior at
low multiplicity region is
ongoing.
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It would be due to tracking?
The highest efficiency would
be the true chamber
efficiency.
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Backup: Iteration analysis
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Position resolution and relation between drift time and drift distance are
required for track reconstruction, but they are unknown at first.
For track reconstruction, they are assumed.
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After track reconstruction, position resolution and relation between drift
distance and drift time are obtained.
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They are results of the track obtained by assumed values, so it is not
obvious if they are correct values.
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Using them, the track reconstruction is done again. Position resolution and
relation between drift distance and drift time are obtained again.
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Doing such things again and again, the values get closer to the true values.
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Backup: RT curve
After the analysis iterated four times
Drift Distance
Drift Distance
No iteration
Drift Time
Drift Time
RT curve: relation between the drift distance (R) and drift time (T)
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Backup: Residual
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