MTD Calibration for Cosmic Ray Triggered Data in RUN 10 at STAR. Lijuan Ruan (BNL), Liang Li (UT Austin) 04/01/2011. Workshop on STAR MTD Production and Related Physics, Hefei, Anhui, China, March 30th - April 1st, 2011 . 1. Motivation.
MTD Calibration for Cosmic Ray Triggered Data in RUN 10 at STAR
Lijuan Ruan (BNL), Liang Li (UT Austin)
Workshop on STAR MTD Production and Related Physics,
Hefei, Anhui, China, March 30th - April 1st, 2011
RUN 10 Au+Au 11 GeV fastoffline production of st_mtd data stream for Reversed Full Field
Selected cosmic ray tiggered events with “cosmic” offline Tigger ID 310803
Global tracks were used
tMTD is calculated by averaging the times from two ends of an MTD strip so that it does not depend on the hit position on the strip.
tTOF1 and tTOF2 are calibrated times associated with TOF hits due to the cosmic ray muons.
tTPC is the calculated time of flight between two TOF trays 1 and 2 with the pathlength and momentum information from TPC.
tSteel is the time of flight from MTD to TOF, also calculated with TPC information
The time difference between TOF+MTD measured time and TPC measured time is
deltaT = (tTOF2 – tTPC + tTOF1)/2 – tMTD - tSteel
Sigma = 0.006 rad
Sigma = 2.5 cm
deltaT0 = tTOF2- tTOF1 – tTPC
TOF timing resolution ~92.9 ps/sqrt(2) ~ 66 ps, close to the result in our intrinsic timing resolution study (M Shao and L Li, International Journal of Modern Physics E, Volume 16, Issue 07-08, pp. 2476-2483 (2007))
The mean value is close to 0
First, we did a T0 offset correction for each strip. Basically we fitted the deltaT
histograms with a Gaussian function and subtracted the obtained mean value
Secondly, we combined all channels and plotted deltaT versus averageTOT=
sqrt(totMtdEast*totMtdWest). The slewing correction curve is obtained by a 4th order
polynomial function fitting the Gaussian mean deltaTs for all averageTOT bins. Then the slewing
correction is done by subracting the function value from tMtd according to its averageTOT value.
The slewing correction is done for only TOT<22 ns because above that the statistics is poor.
A second T0 correction is done thereafter due to the observed T0 shift after the slewing correction
MTD+TOF timing resolution: ~109ps
Timing resolution from TOF: ~46ps
MTD timing resolution: ~99ps