Difference between revisions of "Start Counter Background Studies"

Revision as of 11:19, 21 June 2012

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

Pure EM Background

• Generated 100K dummy events using

$ genphoton -M 100000 -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 to process the events through HDGEANT (from latest sim-recon version) [3]
  • 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 or flux for this minimum energy is 2.2e9 photons/s: BGRATE 2.2
  • 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:

where, is scaling factor, is the time window (BGGATE) in seconds, and is the number of events generated.

• Plots
  • Rates [4]
  • Hit Multiplicity [5]
  • R vs Z hit [6]
  • Y vs X hit [7]

• This study was done for the nominal running luminosity of
• For the high luminosity running of , the BGRATE should be set to 11.0 instead of 2.2. One can either scale the above rates by applying an additional factor of

• Or, one can re-run the study with BGRATE set to 11.0. This "value will be scaled automatically to the right value corresponding to the beam energy threshold defined by the BEAM card." - Sasha

• The plots after applying the above scaling factor are:
  • Rates [8]
  • R vs Z hit [9]
  • Y vs X hit [10]

Pure Hadronic Rates

• To study the pure hadronic rates, a similar method is used compared to the EM background study.
• 395K background events are generated using bggen. The bggen card options are: [11]
• These events are then passed through HDGEANT
  • The BGRATE and BGGATE options are turned off as we don't want to look at photon pile-up
  • No EM processes options 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 [12]
  • Hit Multiplicity [13]
  • R vs Z hit [14]
  • Y vs X hit [15]

• GlueX Wiki » Start Counter » Start Counter Background Studies