Status of TOF Calibration and the future

•Framework•Calibration w/o tracking•PID•Calibration with tracking•Performance•Summary

Akio KiyomichiUniv. of Tsukuba

Tsukuba-Yonsei Workshop December 5, 2000

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]2

Basic Design

• Scintillator: Bicron BC404– decay constant : 1.8 ns

– attenuation length : 160cm

• PMT : Hamamatsu R3478S– rise time : 1.3 ns

– transit time : 14 0.36 ns

• HV Bleeder with chip resisters

PMT

light

light

vtt

x

vltt

t

2

/2

21

210

),( 0 xt

)exp(

/

01

01

x

aa

vxtt light

TimingPulse Height

)exp(

/)(

02

02

xl

aa

vxltt light

{

{{

2)

2()

2(

2)

2()

2(

12221

122210

tvttvx

tttt

lightlight

80 ps

1.3 cm

Scintillator:1.5x1.5x64cm

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]3

TOF Performance at CERN-WA98

~ 85ps

Time-of-Flight [ns]

Used high momentum TOF resolution for all 500 slats

(1996)

• 5 panels of TOF tested at CERN-WA98.• Overall TOF resolution of < 85ps obtained.

– TOF counter ~80ps + Start counter ~30ps

• For PHENIX, we will reach TOF resolution <95ps.– TOF counter ~80ps + BBC counter ~50ps

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]4

TofCalibratorTofCalibrator

Calibration Framework

DST

PRDF

CAMERAreconstruction

PASS:0rough calibration

PASS:1~calibration w/ tracking

• Taking account 8/9 parameter so far

1. Time offset2. Slewing parameter 3. Y position offset4. Light velocity in scint.5. Energy loss conversion factor6. Time conversion factor 7. Charge conversion factor8. TVC/QVC pedestal9. Global Time offset

9 TOF parameter set

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]5

Rough Calibration: Zero-field Run

• Rough calibration parameters obtained. [~200ps level]

– T0 value and Z-vertex information from BBC.

– NO tracking information used yet. (To be done)

– Timing offset, Position offset and Gain Correction

Time offset

y position offset

t = 5 nsec~ length of scinti. 64cm

• BBC Z vertex (-40 < z < 40 cm) are required• L : straight path ( from z-vertex TOF hit position with retracted geometry)• Including BBC Coins, ZDC coins, BBC&ZDC trigger

Calibration condition

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]6

Track matching and TOF intrinsic timing resolution

• TOF-TEC = 2cm:

– Corresponding timing resolution is 120 ps.

– Consistent with TOF intrinsic timing resolution of 120ps operated without slewing correction.

TIME ~ 120 ps

position ~ 2cm

TECPC3TOF

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]7

Particle Identification

• We can see clear ,K,p separation

• No slewing correction• No final timing adjustment

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]8

TOF resolution (before New calibration)

• Select High-momentum pion.• Current Time of Flight resolution is ~170ps.

– BBC, TOF, Tracking Chamber

• No slewing correction yet.• No final adjustment of relative timing offset yet.

~ 170 ps

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]9

TOF Calibration Passes

• Calibration w/o Tracking– pass0: Rough Calibration

• Calibration with Tracking( selection for timing calibration)– pass1: Y-position offset

– pass2: Rough Timing offset

– pass3: Slewing correction

– pass4: Timing offset [slat by slat]

– *pass5: more adjustment position offset

– *pass6: Timing offset [run by run]

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]10

Used DST data

• phs5 + projection

• Run 10726 -12087 (~500K event)

• Statistics: 200~500 hits per slat

•dch_quality>20•dR < 5cm cut•phs5+projection

•0.1 < m2 < 0.1 (pion) for Timing calibration

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]11

pass1: Y-position offset

• Estimate Y-position offset and Light Velocity.– Light Velocity ~15cm/ns

– Y-position offset

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]12

pass2: Rough Timing offset

• Estimate Time offset value based on the pion selection [slat by slat]

• Difference between new and old– 1ns(peak-edge) + 1.4ns(BBC Time-offset)

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]13

pass3: Slewing correction

• We use leading edge discriminator.• Fitting function: y = A + B/sqrt(x)

• Estimate slewing parameters (A,B)– Typical value for WA98

• A = -0.4~ -0.27 ,B = 11~21

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]14

pass4: Timing offset

• Estimate Time offset value based on the pion selection after slewing correction [slat by slat]

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]15

Performance

• Use recent DST (product in Dec.1 - 4)– about 100 files : ~100K event

• Select high momentum pion+– dR<5cm, 0.05<m2<0.1, pt>1.5GeV/c

– TOF - T0(BBC)*0.975 - flighttime(Tracking)

• close to achieve <100ps !?

< 110ps

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]16

Future plan / known problem

• We will get DSTs for whole runs in few weeks.– ~5M event

• We should try – Check Run dependence

– BBC/TOF timing conversion factor.

– Slewing correction using more statistics.

Timing conversion factor gap

Tsukuba-Yonsei workshop Dec. 5, 2000

Akio Kiyomichi [Univ. of Tsukuba]17

Summary

• Calibration code is now available.– We can do iterative process from DST.

• Taking account 8/9 parameters.– Only global time offset is still 0 value.

– It will check by next DST.

• TOF resolution reach < 110 ps in recent DST.(very preliminary)