Comparison of Online and Offline Calibrations



This page compares the online and first offline calibrations.  The online calibration table was generated during data-taking using a single long run processed through fastOffline production and uploaded on March 30th.  It uses slopes to set the relative gains in an eta-ring and then normalizes the eta-rings using MIPs.  The first offline calibration uses a significant fraction of the produced transverse and late longitudinal runs.  It sets the relative gains using MIP peaks and then uses electron E/p to set the absolute scale.  It was uploaded on December 7th.

Body Counts:

138 additonal towers are masked in this first offline calibration, leaving 4517 good towers.  1 tower (2916) was masked before but is now listed as OK.  To be honest, I have no idea why it was masked in the online calib; its slope looks fine to me.


The electron E/p scaling in the offline calibration increased the gains by an approximately uniform 10 percent (more at the edges).  This effect is seen in the following plot of offline E_T - online E_T, integrated over all towers that were good in both calibrations:

Now, the interesting thing is the relative changes of offline-online for the east side and the west side.  If I only plot the location of towers whose gains increased by more than 20% I get

There were only 12 towers whose gains decreased by 20%; all of them were on the west side. Finally here's a plot of the E_T change of the remaining towers:

I think the message here is clear:  the gains on the east side have increased more than the gains on the west side!  It's possible that the use of the online calibration in previous Run 6 jet studies is at least partially responsible for the obsereved east-west jet asymmetry.

To get quantitative about this effect we have to go to 1D.  I've attached a PDF of eta-ring by eta-ring histograms like the first one on this page.  The first two pages are the east side; the next two are the west side.  I've found it easiest to analyze if you set your Reader to view two pages at a time; then you'll be comparing towers with the same absolute value of pseudorapidity when you flip.  The conclusion is pretty clear: at midrapidity the difference in offline - online E_T floats around 5 - 8 GeV on the east side, but it's only about 2 - 5 GeV on the west side.