Time stamping with the TPC
Martin Killenberg
5. Oktober 2010
Martin Killenberg (CERN)
Time stamping with the TPC
1
How does time stamping with the TPC work?
In the barrel it only works in combination
with an external silicon detector
The TPC measures time since beginning of the bunch train
z = (tdrift + BX · ∆tBX ) · vdrift
The silicon sensor measures z directly, without timing information.
From this the time stamp BX · ∆tBX is determined.
Cathode
Anode (Readout)
Silicon Envelope
Martin Killenberg (CERN)
Time stamping with the TPC
2
How does time stamping with the TPC work?
In the end cap the TPC can determine the time stamp stand alone
The fist hit that arrives at the end plate gives the time offset
Cathode
Anode (Readout)
Silicon Envelope
Martin Killenberg (CERN)
Time stamping with the TPC
3
Current status
Shoot muons from the vertex
Run full digitisation and reconstruction
Shift the reconstructed track to a random event within the bunch train
Barrel region:
Calculate intersection of reconstructed helix with silicon envelope
Calculate intersection of MC truth with silicon envelope (cylinder)
Smear SET hit with detector resolution
Calculate time stamp and difference to MC truth
Calculate the bunch crossing from the time stamp
End cap region:
TPC stand alone time stamping (arrival time of first hit)
Vertex is smeared with size of beam packages
Martin Killenberg (CERN)
Time stamping with the TPC
4
Barrel Time Stamping
timeStampHisto
Entries
10000
Mean
-0.2091
RMS
1.588
Difference Reconstructed Time Stamp - MC Time Stamp
Number of Entries
500
400
300
200
100
0
-10
-8
-6
-4
-2
0
2
4
Time Stamp Difference [ns]
6
8
10
Example:
50 GeV muons, λ = 50◦ (corner of the TPC), 100 µm SET resolution
Parameters
3 dip angles: 5.71◦ (tan(λ) = 0.1), 30◦ , 50◦
7 energies (2 – 200 GeV)
4 SET resolutions: 0 µm, 50 µm, 100 µm, 150 µm
Martin Killenberg (CERN)
Time stamping with the TPC
5
Barrel Time Stamping
Width of time stamp difference distribution [ns]
Time Stamping Accuracy (SET Resolution 100 µm)
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
dip angle 5 deg
dip angle 30 deg
dip angle 50 deg
0.2
0
1
10
100
1000
Energy [GeV]
Martin Killenberg (CERN)
Time stamping with the TPC
6
Barrel Time Stamping
Width of time stamp difference distribution [ns]
Time Stamping Accuracy (Dip Angle 5 deg)
3
SET resolution 150 µm
SET resolution 100 µm
SET resolution 50 µm
SET resolution 0 µm
2.5
2
1.5
1
0.5
0
1
10
100
1000
Energy [GeV]
Martin Killenberg (CERN)
Time stamping with the TPC
7
Barrel Time Stamping
Width of time stamp difference distribution [ns]
Time Stamping Accuracy (Muon Energy 50 GeV)
3
SET resolution 150 µm
SET resolution 100 µm
SET resolution 50 µm
SET resolution 0 µm
2.5
2
1.5
1
0.5
0
0
10
Martin Killenberg (CERN)
20
30
Dip angle [deg]
Time stamping with the TPC
40
50
8
Barrel: Determining the Bunch Crossing
Difference Reconstructed BX - MonteCarlo BX
BXOffsetHisto
Entries
10000
Mean
0.152
RMS
2.763
Number of Entries
1400
1200
1000
800
600
400
200
0
-20
-15
-10
-5
0
5
10
Bunch Crossing Difference
15
20
90 % of the muons are reconstructed correctly to ± 5 bunch crossings1
1
Energy 50 GeV, dip angle 5◦ , SET resolution 50 µm
Martin Killenberg (CERN)
Time stamping with the TPC
9
End Cap Time Stamping
Difference Reconstructed Time Stamp - MC Time Stamp
180
timeStampHisto
Entries
5001
Mean
101.4
RMS
8.897
160
Number of Entries
140
120
100
80
60
40
20
0
80
90
100
110
120
Time Stamp Difference [ns]
130
Example: 50 GeV muons, λ = 60◦
Width of distribution O(10 ns)
Much wider than barrel distribution
Measurement depends only on a single point
Single point resolution is lower than track resolution
Offset of O(100 ns) is currently being investigated. Depends on the angle
and the energy.
Can the time stamping be improved using the ETD as external reference?
Martin Killenberg (CERN)
Time stamping with the TPC
10
Conclusions
Barrel
TPC has very good time stamping capability
Time stamping capability strongly depends on SET resolution
Low dependeny on energy and dip angle
TPC track resolution 1.2 ns (perfect SET)
Time stamping resolution < 1.5 ns (SET resolution 50 µm)
90 % of the muons are reconstructed correctly to ± 5 bunch crossings
Not included (yet)
Multiple scattering in field cage (O(10 µm) for 2 GeV muons)
Time of flight effects
End Cap
Single point resolution limits time stamping accuracy to 10 ns
100 ns offset is currently being investigated
Using the ETD might improve the resolution
Martin Killenberg (CERN)
Time stamping with the TPC
11