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STAR TOF Calibration

STAR TOF Calibration. TPC(TPX) - tracking. pVPD/upVPD - start time measurement. MRPC TOF (TOFr) – stop time measurement. 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

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STAR TOF Calibration

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  1. STAR TOF Calibration

  2. TPC(TPX)- tracking pVPD/upVPD - start time measurement MRPC TOF (TOFr) – stop time measurement 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

  3. TOF system pVPD/VPD consists of plastic scintillators + fast PMTs, 5.4~5.7m 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, 94 trays in run IX and all 120 trays in runX

  4. TOF Electronics 2 THUB per side, 4 total 1 TCPU per tray/VPD, 122 total 1 TPMT/TDIS per VPD, 2 total 8 TINO/TDIG per tray, 960 total 24 channel per TINO/TDIG, 23040 total

  5. HPTDC INL Correction Integral Non-Lineraity Diffrential Non-Lineraity

  6. Related software update Calibration results

  7. Leading-edge timing signal, trailing-edge signal width (TOT) Leading-edge trigger, signal charge (ADC) is measured for correction Amp. Amp. Q1 Thre. Thre. Q2 T1lT2l T2tT1t time T1T2 time Time stamp TOF Calibration –runV (and later on)

  8. VPD Collision Point • All hits in the same event arrived at the same time • As reference for each other VPD PMTs

  9. VPD calibration procedure

  10. TDC-TOT correlation TDC1 – (TDC2+TDC3)/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)

  11. Resolution before/after calibration ~6 ns ~0.16 ns Before calibration After calibration TDC1 – (TDC2+TDC3)/2 (ns) TDC1 – (TDC2+TDC3)/2 (ns) Run VIII 200 GeV pp

  12. T0+(L/2+Vz)/c T0+(L/2-Vz)/c East West z CP Beam line Vertex Z upVPD upVPD 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)

  13. 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

  14. Comts TOFmeasured – TOFexpected (ns) T0 correction Run VIII 200 GeV pp Channel-by-Channel Simple Gaussian function Fit Shift the mean of TOFmeasured – TOFexpectedto 0

  15. TOFr TOT slewing correction TOFmeasured – TOFexpected (ns) TOT (ns) Run V 200 GeV CuCu Signal ringing effect Run VIII 200 GeV pp Better signal termination achieved TOT (ns)

  16. Run VIII 200 GeV pp Finite signal propagation speed vs. hit position TOFmeasured – TOFexpected (ns) Hit Position Z (cm) Run V 200 GeV CuCu Readout MRPC strip Hit position (Z) corrction

  17. TOF Time Resolution Run V CuCu 62.4GeV Run V CuCu 200GeV Run VIII pp 200GeV

  18. TOF resolution summary

  19. TOF calibration w/o start detector Fast simulation TOF mean time resolution: 90ps Time-TOT/Z correlation taken from run V CuCu data T0 obtained by direct average of Ti Several iteration of calibration Expectation (ideal)

  20. T0 w/o start detector – from data Run V 62.4 GeV CuCu After 6-round calibration iteration

  21. Summary • Calibration database • INL table • T0 table • T-TOT table • T-Z table • Calibration w/o VPD • Fast simulation • Data results • VPD Calibration • INL correction • Slewing correction • TOF tray Calibration • INL correction • T0 correction • Slewing correction • Hit position correction

  22. BackupSlides

  23. 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

  24. #Events needed for calibration 10 K for slewing correction Note in pp collisions, the upVPD efficiency is only ~40% if requiring >=2 hits on both sides

  25. VPD fired channels Run VIII 200 GeV pp Zebo Tang • ~35% events have >=3 hits on either side (useable for calibration) • ~40% events have >=2 hits on both sides (better start time or • ~15% events have >=3 hits on both sides Vz resolution)

  26. 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

  27. Amp. Q1 Thre. Q2 T1T2 time Calibration Procedure – before run V Leading-edge trigger, signal charge (ADC) is measured for correction

  28. pVPD Calibration –start time

  29. TOFr Calibration –MRPC TA & TZ TA slewing correction Hit position (TZ) correction 7th-order polynomial

  30. Time resolution determination Increase with n (assume equal time resolution for each channel)

  31. Calibrated time resolution

  32. Hadron PID

  33. Electron PID

  34. Muon PID 200 GeV CuCu

  35. Run-VIII PID 1.2<p<1.4 GeV/c

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