Start Counter Background Studies

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  • Seema and Sasha's Old Background Study: [1]
  • Sasha's Howto [2]

EM Background Rates

  • Generated 10K dummy events using
$ genphoton -M 10000 -Pmax 0.00001 -Pmin 0.000005 -Thetamin 0. -Thetamax 0.001 -o file_out.ascii
  • Convert the ascii events into HDDM format and smear the z-vertex across the entire 30cm long target

NB: This step is not necessary as HDGEANT automatically smears the vertex across all three dimensions

$ genr8_2_hddm -V"0 0 50 80" file_out.ascii 
  • Use the following file options to process the events through HDGEANT (from latest sim-recon version)
    • The minimum energy for the photon beam was lowered to 1.2 MeV to look at hits contribution in SC from 50 MeV photons: BEAM 12. 9. 0.0012
    • The background rate is set appropriately depending on the threshold:
      • For 10^{7}\gamma /s use BGRATE 1.1 (HDGEANT scales the BGRATE to 2.22)
      • For 10^{8}\gamma /s use BGRATE 11.0 (HDGEANT scales the BGRATE to 22.2)
    • The photon pileup window is set to 100ns: BGGATE 0. 100.
    • The following EM processes are turned on:
      • Compton Scattering: COMP 1
      • Pair Production: PAIR 1
      • Energy Loss: LOSS 1
  • Additional cuts in HDGEANT:
    • The energy threshold in for hits in SC is 150 MeV (but is currently not applied in HDGEANT code)
    • The time window for two hit resolution is 25 ns
  • The hits are then smeared using mcsmear (???)
  • To obtain the appropriate scaling factor for the plots, use the following approach:

f=1/\delta t/N

where, f is scaling factor, \delta t is the time window (BGGATE) in seconds, and N is the number of events generated.

  • Plots 10^{8}\gamma /s

Hadronic Rates

  • To study the hadronic rates, a similar method is used compared to the EM background study.
  • 395K background events are generated using bggen.
  • These events are then passed through HDGEANT
    • The BGRATE and BGGATE options are turned off as we don't want to look at additional photon pile-up (double counting)
    • The same EM processes as above are turned on
    • The BEAM options are still BEAM 12. 9. 0.0012
    • The output is again smeared using mcsmear
  • No normalization factor is applied
  • The following rates are observed:

Energy Cuts