08 Completed Calibration and Uncertainty


The 2008 Calibraton has been uploaded into the database. I was able to find calibration coefficients for 4420 towers. Of the remaining towers, 353 were MIPless and 27 had spectrums that I could not recover by hand.

This year, differently from previous years, known sources of bias are removed. If an event had a nonHT trigger, the tracks from that event were used for the calibration (even if it had an HT trigger). Most of the triggers were fms slow triggered events. Each eta ring was calibrated separately, and then a correction for each crate was applied. After these corrections, I once again made the cuts on the electrons more stringent. No deviation from E/p =1 was found. With the biases eliminated, we now quote a systematic variance instead of a systematic bias as the uncertainty on the calibration.

The source of this uncertainty are the uncertainties on various fits used for each calibration, namely the MIP peak for each tower, the absolute calibration for each eta ring, and the correction for each crate. These uncertainties are highly correlated. I have completed this calibration by recalculating the calibration table 3,000 times varying the MIP peaks, the eta ring corrrections and the crate corrections each time. Using this method, I was able to determine the correlated uncertainty for each calibrated tower. This uncertainty is, on average, 5%.

This uncertainty is different than the systematic bias quoted for 2005 and 2006. It is a true variance on the calibration. To use this uncertainty, analyzers should recalculated their analysis using test tables generated for this purpose. The variance in the results of these multiple analyses will give a direct measure of the uncertainty due to the calibration scale uncertainty. These tables will be uploaded to the database with the names "sysNN". They should be used before clustering, jet finding, etc.