X. DongAug. 5th, 2010 RNC Group Meeting 1 Barrel Time-Of-Flight In Run10 Xin Dong Many thanks to the...

1X. DongAug. 5th, 2010 RNC Group Meeting

Barrel Time-Of-Flight

In Run10

Xin Dong

Many thanks to the TOF group

2Aug. 5th, 2010 RNC Group Meeting X. Dong

TOF Close-out Review

Reviewed on Aug 10-11, 2009 at BNL. Report can be found here:

http://www.bonner.rice.edu/~eppley/TOF_review_2009/STAR_TOF_closeout_report.pdf

Construction stage -> Operation stage


Run 10 “Summary”

120 full barrel trays installed 119 trays were active in Run 10 (one out due to the HV cable issue) - only 1 dead channel out of ~23000 Start detector (upVPD or VPD) hasn’t changed since last year

VPD coincidence (and vertex selection) widely used as the MB condition at high energy collisions A much cleaner trigger in low energy collisions

TOF multiplicity trigger Central trigger UPC trigger

VPD/TOF operation in Run10 went very well. Preliminary calibrations (based on fast offline) are done, and in db.


η~ 0 η~ 0.9 Z

One Tray

One Module

φ

local Y

local Z

“+” ―To TPC center

Barrel TOF Geometry


Tray Alignment Calibration

Use the low luminosity data taken on day 074Do local (x,y,z) alignment in one loop.

Tray alignment calibration constants were uploaded soon during 62 GeV run. Reflected in the fast offline data.

Open: from fit to allSolid: from fit to modules 1-6 only


Conventional Timing Calibration

1. Calibration for the start detectors - VPDs

2. Calculate the start time

3. Calibration for the BTOF trays

- Need TPC tracking

pp

~ 10 2

tt

~ 10 2 but enhanced by at high p limit


200 GeV and 62 GeV (prel.) calibration

62 GeV200 GeV

85ps 90ps

Difference comes from the start sideBingchu Huang


When Going Down Energy

Solutions:

1) Non-Vpd-Start (BTOF self) calibration algorithm implemented

2) Introduce a truncation algorithm in calculating the start time from VPD to suppress the outliers from slow particles

The conventional VPD-start calibration method has some issues:

1) The small VPD acceptance causes to start losing significant amount of events, even central events.

2) Outliers from slow particles increase dramatically, which will dilute the start time resolution significantly.


“Good” events are identified via offline analysis by requiring a valid vertex within |Vz|<75 cm and |Vxy|<2 cm

~ a few % minbias triggered events are “good” events

VPD trigger rate ~ 2*collision rates within |Vz|<75cm

1/3 of VPD trigger triggered events are “good” events~2/3 of “good” minibias events are labeled as VPD triggers

BBC Minimum bias trigger: efficient but with large backgroundVPD trigger: much cleaner but inefficient (missing central/peripheral)

VPD trigger used as our luminosity monitor

Triggers at 7.7 and 11.5 GeV

AuAu 7.7 GeV


39 GeV - Truncation Calib. in VPD

VPD Timing not symmetric in low energy collisions- single particle hit in each channel- slow particles lead to larger timings

Tdiff = Ti - <Tj>(j!=i)

Use truncated mean in calculating the averaged timing. Remove hits with top 20% high timing - coming from slow particles


39 GeV Calibration

Rafael, Bill

Resolution = 86psWith improved start side


Calibration w/o VPD

Calibration completely w/o VPD62 GeV testVery promising timing resolution! R

esol

utio

n (n

s)

# of pions# of pionsT

- T

exp

(ns

)

TDIG board ID

Res

olut

ion

(ns)

# of pionsMing Shao


Startless Calibration Strategy

Step 1:Obtain the calibration constants (at expert level), two ways: - with the standard VPD start calibration

conventional, but require more statistics due to VPD inefficiency - with the new BTOF self calibration

Step 2:Apply the calibration constants to data - Algorithm with the new BTOF self calibration (maximize efficiency)


Tof

- T

ofe

xp (

ns)

Day 125 7.7 GeV Day 125 7.7 GeV

Applying with BTOF self calib. algorithm

7.7 fast offline data

Calibration constants obtained in 39 GeV with VPD-start calibration procedure.

- Demonstrates the tray stability across different collision systems.



Particle flight time from TOF Track length from TPC

Depend on masses of particles

Can be fitted with Gaussians

default time resolution is 110 ps (Run9), may change with p for proton

PID method (I)

Masayuki Wada

This is the default method in production!


Calculate m2 from

get the probability of being a particle

Currently not in MuDst, people can calculate it by themselves if needed. momentum and position resolution are essentially determined by the

TPC

Dylan TheinMasayuki Wada

1-Sigma error bar

PID method (II) - M2


In progress

PID combining TOF and dE/dx

Masayuki Wada

Yuri Fisyak


pp2pp Run9

Efficiency = (tracks with matchFlag>0) / (tracks that can be projected to TOF modules)

Remarks on Efficiency & Acceptance

Acceptance: eta -0.9 - 0.9 at Vz=0 phi averaged acceptance ~0.87 due to tray gaps

TOF Matching * Acceptance ~ 0.8 * 0.87 ~ 0.7 single track at plateau - Run9 only 86 trays (out of 120), thus total TOF acceptance * efficiency ~ 0.5


Summary

1) Run10 TOF operation went quite well.

2) Preliminary calibrations have been done - Promising performance in various collision energies

High energy datasets (200, 62.4 GeV)- Wait for the final TPC calibration and complete the TOF

calibration for production Low energy production are using the fast offline calibration

- Check the TOF calibration when doing your analysis

3) TOF PidTraits is available in the MuDst for physics analysis now developing an integrated PID algorithm combining TOF+dE/dx+(…)


Calibration Status

Preliminary 200 GeV and 62 GeV calibration were done, and constants were in db.39 GeV calibration were finished, constants will be uploaded to db soon.7.7 GeV calibration is underway (in accumulating enough statistics)

- based on fast offline (preliminary TPC calibration)

Important infrastructure updates:1) Low energy runs: to suppress the outliers from slow particles, introducing a truncation algorithm in calculating the start time from VPD.2) Non-Vpd-Start (BTOF self) calibration algorithm is implemented in the calibration maker to allow the BTOF self calibration.

Fast offline QA - Ulisses Gulart, Rafael Derradihttp://www.star.bnl.gov/protected/lfspectra/usouza/TofQA/web/tofQA_woCalib_day126.html

Vpd-start calibration - Rafael Derradi, Bingchu Huang, Bill LlopeNon-vpd-start calibration - Ming Shao, Bill Llope


Applying with BTOF self calib. algorithm

62 GeV:Constants from the Vpd-Start calibration in data base

(alignment not updated when these constants were obtained)

62 GeV


How to load TOF calibration

…gSystem->Load("StBTofUtil");gSystem->Load("StVpdCalibMaker");gSystem->Load("StBTofCalibMaker");

StChain *chain = new StChain("StChain");

StMuDstMaker *muDstMaker = new StMuDstMaker(0,0,"",fileList,"MuDst.root",nfiles);

St_db_Maker *dbMk = new St_db_Maker("db","MySQL:StarDb","$STAR/StarDb","StarDb");

StVpdCalibMaker *vpdCalib = new StVpdCalibMaker();vpdCalib->setMuDstIn();

StBTofCalibMaker *btofCalib = new StBTofCalibMaker();btofCalib->setMuDstIn();

StMyMaker *myMaker = new StMyMaker();…


Introduce xLocal

Bingchu Huang

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X. DongAug. 5th, 2010 RNC Group Meeting 1 Barrel Time-Of-Flight In Run10 Xin Dong Many thanks to the...

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