STAR time-of-flight detector Calibration

April 27-29, Hangzhou 1

STAR time-of-flight detector Calibration

Ming SHAO USTC


DetectorsTPC(TPX)- tracking

MRPC TOF (TOFr) – stop time measurement

pVPD/upVPD - start time measurement

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


TOF system

pVPD/upVPD 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 and 94 trays in run IX

Run VRun VIIIRun IX

MRPC TOF

TPCX

Y

TPC pVPDpVPD upVPDupVPDZ


New TOF electronics

Start Detector

TOF Tray

TDIG TDIG

TCPU

DIFFERENTIAL DATA AND CLOCK

TINO TINO

MRPC MRPC

COMMANDS

48 CHAN

48 CHAN

48 CHAN

TRAY CAN BUS

MULTIPLICITY

THUB

COPPER: DATA, SAMPLE CLOCK, RESET TRIGGER STROBE & DATA

TOP LEVEL CAN BUS

COPPER LINKS TO 29 TRAYS

RHIC CLOCK

SIU FIBER

CAN BUS TO 29 TRAYS

TCD

DAQ

48 CHAN

4

L0 Trigger

4

PMTs TPMT TDIS TCPU

Diff. Data & Clk

Local CANbus

Co

pp

er:

Da

ta,

Sa

mp

le C

lk,

Re

set

Trg

Str

ob

e &

Da

ta

Reset & ClockFrom other THUBs

Reset & ClockTo other THUBs

2 THUB per side, 4 total 1 TCPU per tray/pVPD, 122 total

1 TPMT/TDIS per pVPD, 2 total8 TINO/TDIG per tray, 960 total

24 chn. per TINO/TDIG, 23040 total

Schambach Jo et al., Int. J. Mod. Phys. E 16 2496


HPTDC INL Correction

Jing Liu

Integral Non-Linearity

Differential Non-Linearity


Time-TOT Correlation

Leading-edge timing signal, trailing-edge signal width (TOT)

time

Amp.

T1l T2l T2t T1t

Thre.

Time stamp

Leading-edge trigger, signal charge (ADC) is measured for correction

time

Amp.

T1 T2

Thre.

Q1

Q2


update

Calibration results

Related software

Thanks Xin Dong etc.


VPD

Collision Point

VPD PMTs

W.J. Llope

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


VPD calibration procedure


TDC-TOT correlation

Use spline fit (3rd polynomials TSplineFit based on ROOT, developed by François-Xavier Gentit)

Run VIII, 200 GeV ppRun V, 62.4 GeV CuCu

TD

C1 –

(T

DC

2+T

DC

3)/2

(n

s)

TOT (ns)TOT (ns)


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)

Beam line

Vertex Z

zT0+(L/2-Vz)/cT0+(L/2+Vz)/cWest East

upVPDupVPD

CP

1 1

( ) ( / / ) / 2e wi N j N

ei e wj wi j

Vz VPD t N t N c

1 1

( ) /e wi N j N

ei wj e wi j

starte w

t t N N Vz c

TN N


Resolution before/after calibration

~6 ns ~0.16 ns

Bef

ore

cali

brat

ion

After

calibration

TDC1 – (TDC2+TDC3)/2 (ns)

TDC1 – (TDC2+TDC3)/2 (ns)

Run VIII200 GeV pp

Zebo Tang


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)

TOFr Calibration procedure

• Try channel-by-channel first• Not enough statistics? Then

try module-by-module, or board-by-board


T0 correction

TOFmeasured – TOFexpected (ns)

Com

ts

Channel-by-ChannelSimple Gaussian function FitShift the mean of TOFmeasured – TOFexpected to 0

Run VIII200 GeV pp

Zebo Tang


TOFr TOT slewing correction

Run V 200GeV CuCuSignal ringing effect

Run VIII 200GeV ppBetter signal termination achieved

TOT (ns)

TOT (ns)

TO

Fm

easu

red

– T

OF

exp

ecte

d (n

s)


Hit position (Z) corrction

TO

Fm

easu

red –

TO

Fex

pec

ted

(ns)

Hit Position Z (cm)

Run V 200 GeV CuCu

Run VIII 200 GeV pp

MRPC stripMRPC stripReadoutReadout

Finite signal propagation speed vs. hit position


TOF Time Resolution Run V CuCu 62.4GeV

Run V CuCu 200GeV

Run VIII pp 200GeV


TOF resolution summary

Operation conditionTime Resolution (ps)

pVPDTOFr

(overall)TOFr

(stop time)

Run III200GeV d+Au ~85 ~120 ~85

200GeV p+p ~140 ~160 ~80

Run IV

62GeV (Au+Au) ~55 ~105 ~89

200GeV (Au+Au)

FF/RFF ~27 ~74 ~70

HF ~20 ~74 ~71

Run V200GeV Cu+Cu (TOT) ~ 50 ~92 ~7562GeV Cu+Cu (TOT) ~ 82 ~125 ~94

Run VIII200 GeV d+Au NA NA NA

200 GeV p+p (TOT) ~83 ~112 ~75

Run IX 500 GeV p+p ~85 ~110 ~77


Output calibration parameter

• 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

Bin boundarySame statistics in each bin


#Events needed for calibration

Collisions <dNchraw/d>a

rXiv:

0808.2041

×1/4(pure pion)

×80% (match)

×2 ()

Useable hits per channel

#Events for

channel-by-

channel

#Events for

module-by-

module

#Events for

board-by-

board

#Events for T0

(500/channel

)

p+p (MB) 2.4 0.96 4.2e-5 240 M 40 M 10 M 12 M

d+Au(MB) 10.2 4.1 1.8e-4 56 M 9.3 M 2.3 M 2.8 M

Au+Au(MB) 200 80 3.5e-3 2.9 M 0.5 M 0.12 M 0.15 M

Au+Au

(0-10%)

515 206 8.9e-3 1.2 M 0.2 M 0.05 M 0.06 M

10 K for slewing correction

Note 1: in pp collisions, the upVPD efficiency is only ~40% when requiring >=2 hits on both sides

Note 2: dN/d asymmetry in dAu collisions


Expectation (ideal)

TOF calibration w/o start detector

nTTtofZcorTOTcorTDCTn

i iiiii

10__

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


T0 resolution w/o start detector – from data

expected) (as ps74~0

2ps74~0

T

nTTi

60ps) :(expected ps63~0

3ps89~0

T

nTTi

n

i i

n

i iiii tofZcorTOTcorTDCT1

2

1

2 __0

Run V 62.4 GeV CuCu

After 6-round calibration iteration


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

TThhaannkk yyoouu !!


Backup Slides


VPD fired channels

• ~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)

Run VIII200 GeV pp

Zebo Tang


Track projection and Vz correlation

2D DCA

Beam line uncalibrated, fix to (0.5,0) cmShould be different between fillsUnnecessary to parallel to z direction

Vertex from track projection (No vertex from TPX ): project tracks matched to TOF hits, get the closest position to beam line.


Calibration Procedure – before run V

Leading-edge trigger, signal charge (ADC) is measured for correction

time

Amp.

T1 T2

Thre.

Q1

Q2


pVPD Calibration – start time

xdx

c

x

baxf


TOFr Calibration – MRPC TA & TZ

TA slewing correction Hit position (TZ) correction

2x

e

xx

d

x

c

x

baxf

7th-order polynomial


Time resolution determination

332~

22~

0

321

21

nTTT

nTT

TTi 35.1~

22~

0

nT

nT

TT

i

i

i

Increase with n (assume equal time resolution for each channel)

320~3~

20~2~

0

nTTT

nTTT

T

ii

ii


Calibrated time resolution


Hadron PID


Electron PID


Muon PID

200 GeV CuCu


Run-VIII PID

1.2<p<1.4 GeV/c

Documents

STAR time-of-flight detector Calibration