Barrel Time-Of-Flight In Run10. Xin Dong. Many thanks to the TOF group. 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.
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Many thanks to the TOF group
Reviewed on Aug 10-11, 2009 at BNL. Report can be found here:
Construction stage -> Operation stage
- only 1 dead channel out of ~23000
“+” ―To TPC center
Use the low luminosity data taken on day 074
Do 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 all
Solid: from fit to modules 1-6 only
- Need TPC tracking
but enhanced by at high p limit
Difference comes from the start side
The conventional VPD-start calibration method has some issues:
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.
Non-Vpd-Start (BTOF self) calibration algorithm implemented
Introduce a truncation algorithm in calculating the start time from VPD to suppress the outliers from slow particles
BBC Minimum bias trigger: efficient but with large background
VPD trigger: much cleaner but inefficient (missing central/peripheral)
VPD trigger used as our luminosity monitor
“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
1/3 of VPD trigger triggered events are “good” events
~2/3 of “good” minibias events are labeled as VPD triggers
AuAu 7.7 GeV
VPD trigger rate ~ 2*collision rates within |Vz|<75cm
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
Resolution = 86ps
With improved start side
Calibration completely w/o VPD
62 GeV test
Very promising timing resolution!
# of pions
T - Texp (ns)
# of pions
# of pions
TDIG board ID
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
Apply the calibration constants to data
- Algorithm with the new BTOF self calibration (maximize efficiency)
7.7 fast offline data
Calibration constants obtained in 39 GeV with VPD-start calibration procedure.
- Demonstrates the tray stability across different collision systems.
Tof - Tofexp (ns)
Day 125 7.7 GeV
Day 125 7.7 GeV
default time resolution is 110 ps (Run9), may change with p for proton
This is the default method in production!
Dylan TheinMasayuki Wada
Currently not in MuDst, people can calculate it by themselves if needed.
1-Sigma error bar
= (tracks with matchFlag>0)
/ (tracks that can be projected to TOF modules)
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
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 Derradi
Vpd-start calibration - Rafael Derradi, Bingchu Huang, Bill Llope
Non-vpd-start calibration - Ming Shao, Bill Llope
Constants from the Vpd-Start calibration in data base
(alignment not updated when these constants were obtained)
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();
StBTofCalibMaker *btofCalib = new StBTofCalibMaker();
StMyMaker *myMaker = new StMyMaker();