Start Counter Background Studies

• 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 control.in 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 $10^{8}\gamma /s$
  • Rates [3]
  • Hit Multiplicity [4]
  • R vs Z hit [5]
  • Y vs X hit [6]
  • Energy [7]

• Plots $10^{7}\gamma /s$
  • Rates [8]
  • Hit Multiplicity [9]
  • R vs Z hit [10]
  • Y vs X hit [11]
  • Energy [12]

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:
  • Rates [13]
  • Hit Multiplicity [14]
  • R vs Z hit [15]
  • Y vs X hit [16]
  • Energy [17]

Energy Cuts

• E > 0.2 MeV
  • EM only [18]
  • Hadronic [19]
• E > 0.3 MeV
  • EM only [20]
  • Hadronic [21]

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