Run 4 BTOW Calibration



The recalibration of the BEMC towers for Run 4 includes the following improvements:

  • recovery of 158 swapped towers
  • identification and removal of 38 towers with possible light leakage / electronics problems
  • identification and removal of 24 towers with bad p/E distributions
  • MIP calibration restricted to low-multiplicity events from minimum-bias data
  • isolation requirement imposed on MIP candidates


  • p0 * 4066 = 28.5 GeV full-scale at zero rapidity (assuming pedestal~30).
  • 2191/2400 = 91.3% of the towers have nonzero gains.
  • Despite the differences in the cuts used, the final gains are similar to the ones currently found in the DB; a histogram of (newgain-dbgain)/newgain for the towers present in both calibrations yields a mean of 0.019 and an rms of 0.03896.


The offline calibration of the BEMC towers for Run 4 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, all electrons in all eta-rings are grouped together and the ratio of their energy and momentum (E/p) is plotted, with the energy calculated from the rescaled gains in the second step. The distribution is fit with a Gaussian and a scale factor is applied so that this Gaussian is centered exactly on 1.000.

Catalog query:

<inputURL="||P05ib||P05ic,sanity=1,tpc=1,emc=1, trgsetupname=ProductionMinBias||productionLow||productionMid||productionHigh,filename~physics, filetype=daq_reco_mudst,magscale~FullField,storage!~HPSS,runnumber>=5028057" nFiles="all" />

Working directories:



MIP Cuts:

  • track momentum > 1
  • track enters, exits same tower
  • 1 track / tower
  • (ADC - ped) > 2*pedRMS
  • trigger == 15007 (mb data)
  • abs(z-vertex) < 30
  • reference multiplicity < 57 (60-100% centrality)
  • isolation cut (all neighboring towers satisfy (ADC-ped) < 2*pedRMS)

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
  • trigger != 15203 (excludes most ht-triggered electrons; should have been trigger == 15007 to get mb-only data)
Adam Kocoloski, 14 Feb 2006