In the 2003+2004 jet cross section and A_LL paper we quoted a 5% systematic uncertainty on the absolute BTOW calibration.  For the 2005 jet A_LL paper there is some interest in reducing the size of this systematic.

I went back to the electron ntuple used to set the absolute gains and started making some additional plots.  Here's an investigation of E_{tower} / p_{track} versus track momentum.  I only included tracks passing directly through the center of the tower (R<0.003) where the correction from shower leakage is effectively zero.

Full set of electron cuts (overall momentum acceptance 1.5 < p < 20.):

dedx>3.5 && dedx<4.5 && status==1 && np>25 && adc>2*rms && r<0.003 && id<2401

I forgot to impose a vertex constraint on these posted plots, but when I did require |vz| < 30 the central values didn't really move at all.




Here are the individual slices in track momentum used to obtain the points on that plot:







Electrons with momentum up to 20 GeV were accepted in the original sample, but there are only ~300 of them above 6 GeV and the distribution is actually rather ugly.  Integrating over the full momentum range yields a E/p measurement of 0.9978 +- 0.0023, but as you can see the contributions from invididual momentum slices scatter around 1.0 by as much as 4.5%

Next Steps?  -- I'm thinking of slicing versus eta and maybe R (distance from center of tower).