Hello hps-software,

I have been examining the background rates for the 2.2 GeV data. It appears that the beam is not hitting at the correct spot, but is pushed too far to the electron side. To show this, I have included two background rate plots from the 6.6 GeV data (which appears correct; see "CalorimeterHits_0100_6pt6.
pdf") versus the 2.2 GeV data (which appears offset; see "CalorimeterHits_0100_2pt2.pdf").

To determine what caused this, I first examined the detector and the path the particles take going through it. I fired photons, electrons, and positrons through the detector (I used the 2.2 GeV V4 detector, since the V5 is still a working version) at 30.5 mrad. All the particles appeared to go where they should, so the detector geometry does not appear to be at fault.

To test the input data, I took a background StdHEP file (I used "egs_2.2gev_0.00125x0_200na_
1mb_0mr_10.stdhep") and extracted the momentum of each particle from it and plotted a histogram of px/pz (arctan(px/pz) should be the angle of the beam). It appears that the distribution is a more-or-less Gaussian curve centered around 0 radians with some extra noise at the bottom (probably scattered particles). I included the photon plot (with Gaussian). From my understanding, the input beam should be angled at 30.5 mrad. Also of note, performing the same analysis on a 6.6 GeV background file results in the Gaussian being centered around the expected 30.5 mrad angle. I have also included the photon plot for this. Is there a way to tell SLIC to rotate the 2.2 GeV background input, or am I using the wrong file?

I was unable to check the LCSim output to see if this same distribution occurs there, however, because I am unsure how to loop over an LCIO file programmatically in JAS3. Is there a way, using JAS3's script interface, to load an LCIO file as an ITuple so that it can be looped over, or can JAS3 only open them to look through manually?



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