STAR timeofflight detector Calibration

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STAR time-of-flight detector Calibration

• Ming SHAO
• USTC

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Detectors
Particle momentum dE/dx
8 resolution ?/K separation to 0.6GeV/c k/p
separation to 1.0GeV/c
Aim at 100ps time resolution (TOF system) ?/K
separation to 1.6GeV/c k/p separation to
3.0GeV/c
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TOF system
Run V
Run VIII
Run IX
Z
pVPD
pVPD
upVPD
upVPD
MRPC TOF
pVPD/upVPD consists of plastic scintillators
fast PMTs, 5.45.7m from TPC geometry center
along the beam line 3 channels each side (runV
and before) to 19 channels each side (after runV)
Full barrel TOF consists of 120 trays, 32 MRPC
modules per tray, 6 channels per module Only one
tray in run V, 5 trays in run VIII and 94 trays
in run IX
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New TOF electronics
2 THUB per side, 4 total 1 TCPU per tray/pVPD,
122 total 1 TPMT/TDIS per pVPD, 2 total 8
TINO/TDIG per tray, 960 total 24 chn. per
TINO/TDIG, 23040 total
Schambach Jo et al., Int. J. Mod. Phys. E 16 2496
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HPTDC INL Correction
Integral Non-Linearity
Differential Non-Linearity
Jing Liu
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Time-TOT Correlation
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Related software
update
Calibration results
Thanks Xin Dong etc.
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VPD
W.J. Llope
Collision Point

• All hits in the same event arrived at the same
  time
• As reference for each other

VPD PMTs
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VPD calibration procedure
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TDC-TOT correlation
TDC1 (TDC2TDC3)/2 (ns)
Run VIII, 200 GeV pp
Run V, 62.4 GeV CuCu
TOT (ns)
TOT (ns)
Use spline fit (3rd polynomials TSplineFit based
on ROOT, developed by François-Xavier Gentit)
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Global offset tune

• Slewing effect correction was done on east/west
  side separately
• Absolute time from east/west side are floating
• Tune the global offset between east/west side to
  match Vz(VPD) with Vz(TPC)

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Resolution before/after calibration
Zebo Tang
6 ns
0.16 ns
Before calibration
After calibration
TDC1 (TDC2TDC3)/2 (ns)
TDC1 (TDC2TDC3)/2 (ns)
Run VIII 200 GeV pp
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TOFr Calibration procedure

• Choose ? sample by limiting dE/dx and momentum
  range (or pre-calibrated TOF)
• T0 correction, different cable length and signal
  transition time
• TOFr TOT and Z position calibration, using
  charged pion sample.
• Iteration several times (if needed)

• Try channel-by-channel first
• Not enough statistics? Then try module-by-module,
  or board-by-board

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T0 correction
Zebo Tang
Run VIII 200 GeV pp
Channel-by-Channel Simple Gaussian function
Fit Shift the mean of TOFmeasured TOFexpected
to 0
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TOFr TOT slewing correction
TOFmeasured TOFexpected (ns)
TOT (ns)
Run V 200GeV CuCu Signal ringing effect
Run VIII 200GeV pp Better signal termination
achieved
TOT (ns)
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Hit position (Z) corrction
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TOF Time Resolution
Run V CuCu 62.4GeV
Run V CuCu 200GeV
Run VIII pp 200GeV
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TOF resolution summary
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Output calibration parameter
Bin boundary
Same statistics in each bin

• Inconvinient to retrieve and use the parameters
  of all of the Splines
• Upload each TOT bin boundaries and the
  corresponding corrections
• Interpolate in each TOT bin

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Events needed for calibration
10 K for slewing correction
Note 1 in pp collisions, the upVPD efficiency
is only 40 when requiring gt2 hits on both
sides Note 2 dN/d? asymmetry in dAu collisions
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TOF calibration w/o start detector

• Fast simulation
• Single channel resolution 90ps
• Time-TOT/Z correlation taken from real data
• T0 obtained by direct average of Ti
• 6 iteration of calibration

Expectation (ideal)
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T0 resolution w/o start detector from data
Run V 62.4 GeV CuCu
After 6-round calibration iteration
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Summary

• VPD Calibration
• INL correction
• TOT correction
• TOF tray Calibration
• INL correction
• T0 correction
• TOT correction
• Hit position (Z) correction

• Calibration database
• INL table
• T0 table
• T-TOT table
• T-Z table
• Calibration w/o VPD
• Fast simulation
• Data results

Thank you !
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Backup Slides
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VPD fired channels
Run VIII 200 GeV pp
Zebo Tang

• 35 events have gt3 hits on either side
  (useable for calibration)
• 40 events have gt2 hits on both sides
  (better start time or
• 15 events have gt3 hits on both sides Vz
  resolution)

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Track projection and Vz correlation
Vertex from track projection (No vertex from TPX
) project tracks matched to TOF hits, get the
closest position to beam line.
Beam line uncalibrated, fix to (0.5,0) cm Should
be different between fills Unnecessary to
parallel to z direction
2D DCA
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Calibration Procedure before run V
Leading-edge trigger, signal charge (ADC) is
measured for correction
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pVPD Calibration start time
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TOFr Calibration MRPC TA TZ
TA slewing correction
Hit position (TZ) correction
7th-order polynomial
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Time resolution determination
Increase with n (assume equal time resolution for
each channel)
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Calibrated time resolution
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Hadron PID
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Electron PID
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Muon PID
200 GeV CuCu
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Run-VIII PID
1.2ltplt1.4 GeV/c