25 Mar 08 GCR Meeting Notes

LPTA (Fred/Johann/Claudia)
- Can GCRcalib help to calibrate ACD HI charge scale?
  I (Fred P.) modified the compiled macro I used to analyse the GCR events in opssim2 data, and added the reading of digi events (now it reads merit, gcr and digi files). I obtained the spectrum of each PM of each tile when GCRcalib is able to infer a value for the atomic number Z. The plots below show the low-range and high-range spectrum (top and medium plots) for all species, and the high-range spectrum for events tagged as carbons (bottom plots). This is for the PMT A of the central tile at the top of the ACD (left panel) and of the central tile (2nd row, 3rd column) of an ACD side (right panel). The collection time is 43h.
  
  The spectra do not exhibit any clear signature of heavy ions, probably due to all the "stuff where a bunch of particles leave the side of the ACD and cause a pile up of charge" (E. charles), especially in high-energy events. So the next step will be to correlate these results with AcdTrkHitPoca in ACD recon, in order to only keep the hits which have a suitable DOCA to Tkr1 track.
- Protons/Heliums : In order to evaluate the possibilities to extract protons and He for use in GCRCalib, we looked at the various OBF trigger rates, using ~881 sec. from the BigRun simulations (id est ~440 merit files). The resulting table shows the rate of EM (e+/e-/gamma), Protons, Helium, and Ions (Z>2) events passing each filters and each pair of filters :
  
  Thus, it seems natural to concentrate on GAM and DFC filters, which do not share many events and so could be added in principle. For these 2 filters, we looked at the distribution of events for 2 set of cuts: a)Top CalEnergyRaw>15&&TkrNumTracks>0, and b)Bottom same plus abs(1-CalELayer0/CalELayer1)<0.3&&abs(1-CalELayer2/CalELayer1)<0.3 . The color code is : em, protons, helium, ions. The results are: