Recalibration Using pp data
Originally posted 26 September 2005
Catalog query:
input URL="catalog:star.bnl.gov?production=P05if,tpc=1,emc=1,trgsetupname=ppProduction,filename~st_physics,filetype=daq_reco_mudst,storage=NFS" nFiles="all"
note: 3915/4240 = 92.3% of the available towers were able to be used in the calibration. Lists of bad/weird towers in the pp run are available by tower id:
bad_towers_20050914.txt
weirdtowers_20050914.txt
The relative calibration procedure for pp data is identical to the procedure we used to calibrate the barrel with CuCu data (described below). The difference between pp and CuCu lies in the electron calibration. In the pp data we were able to collect enough electrons on the west side to get an absolute calibration. On the east side we used the procedure that we had done for the west side in CuCu. We used a function that goes like 1/sin(theta) to fit the first 17 eta rings, extrapolated this function to the last three eta rings, and calculated the scale factors that we should get in that region. Here is a summary plot comparing the cucu and pp calibrations for the 2005 run:
Comparing the first two plots, one notices immediately that many of the pp gains on the east (eta < 0) side are quite high. A glance at the last plot on the summary canvas reveals a collection of towers with phi < -pi/2 that have unusually high gains. These towers were added during the pp run and hence their gains are based on nominal HV values without any iteration (thanks Mike, Stephen). If we mask out those towers in the summary plot, the plots look much more balanced:
The bottom plot clearly shows that the final pp gains are ~10% higher than the gains established from the mip calibration using the cucu data. Moreover, the cucu data closely follows a 1/sin(theta) curve, while the curve through the pp data is flatter. This is revealed in the shape of the bottom plot. Note that we never scaled the gains near eta=-1 for the cucu data, which is why there is still a significant drop-off in the ratio of the mean gains in that region.
New calibration and status tables (including the gains for the new towers that were turned on during pp running) are available at
bemcCalib.20050322.000001.root
bemcStatus.20050322.000001.root
It should be noted that the scale factors we used to get the final gains near eta=-1 on the east side were calculated without the new towers since they were throwing off the fit function. However, those new towers still had their final gains scaled before we produced the calibration and status tables.