Goal: Use mips from pp minbias events to set absolute gains for EEMC towers, SMD strips, and all pre- and post-shower tiles for the 2006 run.
Basic Method:
A) Dead / unusable channels
The total number of channels that needed to be masked out for this analysis, and for which no gains were determined, was very small. These channels are either not included in the EEMC gains database (for towers) or have gains and errors entries of -2 and 0 (for all MAPMT / PIX channels). A list of the SMD channels that were masked out in the first-pass analysis can be viewed here. After recovering many of the low-statistics strips, the final list of all channels (towers, pre/post, SMD) that could not be analyzed, and a brief description of the problem encountered, can be found here.
B) Relative yields of SMD strips, using slopes
Most strip spectra are very clean. Typical spectrum is shown below:
ADC pedestal and single photoelectron peak are clearly visible. Determination of slope was fairly insensitive to choice of fitting range ® channels 40-140 used here.
Complete sets of fitted spectra, and tables of individual strip gains and errors, are available here. From checking plots by eye, searching gain tables for anomalies, we conclude that only 17 strips out of ~7000 are not usable, beyond the 40 'known' unconnected strips (16 associated with `notches,' 24 from strip number 288). Using 1st-pass gains, no masking, most sectors look very good in terms of uniformity:
C) 1st pass SMD - absolute gains
By comparing to last year's final SMD results, after absolute gains had been set using the technique described on Jan's web page (see items 11 and 12), we find a systematic difference of about 10% in the slopes obtained. Given that the 2005 results were based on Cu-Cu minbias events, while in 2006 we are using pp minbias (different occupancies, different luminosities), this does not seem unreasonable. To account for this, we have simply increased the (empirically determined) ADC ® energy conversion factor by 10%. Comparison of database gains for 2006 to those for 2005, for two typical planes:
Actual 2006 gains for plane 05U (to show range of strip-to-strip variations)
Note: These intermediate gain values should generally not be used for analysis, now that final SMD gains for 2006 are completed! The 1st pass values are loaded in the EEMC database with a 'flavor' of slope2006 ; if used, log file should contain entries of "prelim, invSlope from day89, absScale match to 2005, for 2006 pp, Scott1". For final gain values (see discussion below), flavor = ofl, and log entry should be "final 2006 p+p, using MIP UxV 7vetoXX7veto, from day 89, Scott".
With SMD gains set at roughly 10% level, and with problem channels (SMD strips, towers, and pre/post layers) masked out, check for events with a "mip ID". In each of the 12 sectors:
D) Absolute pre- and post-shower gains
Because passage of a minimum ionizing particle will result in only a small number of photoelectrons (~3) being collected for these components, spectra were fit using a Landau distribution. Absolute gains were determined assuming that the calculated energy deposition would correspond to an ADC value of 1.46 x MPV (most probable value) found in Landau fit.
Complete sets of histograms and fits, and tables of all final gains as loaded into the database, can be accessed below:
preshower-1 | spectra and fits | gain tables |
preshower-2 | spectra and fits | gain tables |
postshower | spectra and fits | gain tables |
E) Absolute tower gains
To determine the tower gains as accurately as possible, more care was taken in the fitting and QA procedures, relative to those used for the pre- and post-shower layers. Specifically:
Complete sets of histograms and fits, and final gain tables, can be accessed below:
EEMC towers | spectra and fits | gain tables |
The absolute gains deduced via these procedures for all 720 towers are compared to their "ideal" values (ET = 60 GeV) for each eta bin in the figure below:
F) Absolute tower gains - comparison to other results