Introduction

The final BTOW calibration for Run 5 offers the following improvements over previous database calibrations:

• recovery of 194 swapped towers
• identification and exclusion of 51 towers with correlated firing problems
• identification and exclusion of 33 towers with p/E~0.6
• exclusion of 58 towers with PMTs replaced by Stephen and Oleg during the shutdown
• isolation cut removes background from MIP spectra, identifies correlated towers
• 30 cm vertex cut introduced to reduce path length differences among MIPs
• uniform scale factor (1.04613) introduced after eta ring electron normalization to set E/p==1 when integrated over all towers

p0 = 0.00696912 for the fit parameter implies an <ET> = 28.3 GeV on the west side, but the gains do not seem to be well described by the 1/sin(theta) fit

3997/4240 = 94.3% of commissioned towers have nonzero gains

Procedure

The offline calibration of the BEMC towers for Run 5 is accomplished in three steps. In the first step, MIPs are collected for each tower and their pedestal-subtracted ADC spectra are plotted. The MPV of the distribution for each tower is translated into a gain using an equation originally established by test-beam data (SN 0433). In the second step, electrons are collected for each eta-ring and the ratio of their momentum and energy (with the energy calculated using the MIP gains from step 1) is plotted as a function of the distance between the track and the center of the tower. The calculated curve is fit to a GEANT simulation curve, allowing extraction of scale factors for the MIP gains in each eta ring. Finally, electrons in all eta-rings that pass through the center of a tower are grouped together and the ratio of their energy and momentum (E/p) is plotted, using the energy calculated from the rescaled gains in the second step. The ditribution is fit with a Gaussian and a scale factor is applied so that this Gaussian is centered exactly on 1.000.

Catalog query:

Working directories:

The 2005 directory contains jobs run using Dave Relyea's offline pedestals (the bulk of the data), while the earlyfiles directory uses online pedestals for runs before April 26th that are not included in the offline pedestal calculations.

MIP Cuts:

• track momentum > 1
• track enters, exits same tower
• 1 track / tower
• (ADC - ped) > 2*pedRMS
• abs(z-vertex) < 30
• isolation cut (all neighboring towers satisfy (ADC-ped) < 2*pedRMS)
• no trigger selection (previous statement of mb-only triggers was in error)

Electron Cuts:

• 1.5 < track momentum < 20
• track enters, exits same tower
• 1 track / tower
• # track points > 25
• 3.5 < dEdx < 4.5 keV/cm
• (ADC - ped) > 2*pedRMS
• no trigger selection

For More Information:

Detailed information on this and other BTOW calibrations, including tower-by-tower MIP and p/E spectra and a summary of outstanding issues, is available at

http://www.star.bnl.gov/protected/spin/kocolosk/barrel_calibration/saved_tables/

The calibration summarized here has the timestamp 20050101.000001.