Difference between revisions of "HOWTO to generate electromagnetic background"

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This page contains some general descriptions of the generation procedures
 
This page contains some general descriptions of the generation procedures
 
of electromagnetic background. There are several parameters which has to be
 
of electromagnetic background. There are several parameters which has to be
set in the control.in to handle the simulation:
+
set up in the control.in to handle the simulation:
  
 
*  BEAM  12. 9.  
 
*  BEAM  12. 9.  
  Electron beam energy and position of the coherent Bremsstrahlung peak
+
  Electron beam energy and position of the coherent Bremsstrahlung peak.
  
 
*  BGRATE  11.0  
 
*  BGRATE  11.0  
 
  The rate of background photons in GHz (in the Tagger region before the collimator).  
 
  The rate of background photons in GHz (in the Tagger region before the collimator).  
  This parameter should be set to 1.1 or 11.0 corresponding to the tagged photon beam intensities
+
  This parameter should be set either to 1.1 or 11.0 which would correspond to intensities
of 10^7 and 10^8 photons/sec on target, respectively. For high-luminosity runs one should use 11.0.
+
  of the tagged photon beam of 10^7 and 10^8 photons/sec on target, respectively. For  
 +
high-luminosity runs one should use 11.0.
  
*  BGGATE -50. 50.
+
*  BGGATE   -50.   50.
 
  Time interval in the ns, the earliest and the latest time, where the background photons are  
 
  Time interval in the ns, the earliest and the latest time, where the background photons are  
 
  produced. This parameters is used to simulate electromagnetic pile-up events.
 
  produced. This parameters is used to simulate electromagnetic pile-up events.
  
 
*  EBREMS_MIN 0.12
 
*  EBREMS_MIN 0.12
  The low energy of generated Bremsstrahlung photons can be set using EBREMS_MIN card. If EBREMS_MIN  
+
  The low energy of generated Bremsstrahlung photons. If EBREMS_MIN is commented, or set to 0,  
is commented, or set to 0, the default photon-energy threshold of 0.12 GeV is used. If EBREM_MIN is  
+
the default photon-energy threshold of 0.12 GeV is used. If EBREM_MIN is set, the rate of  
set, the rate of background photons is automatically scaled as follows:
+
generated background photons is automatically scaled as follows:
       Rate(E_gamma > Thr)  =  Rate(E_gamma = 0.12 Gev) *k,
+
       Rate(E_gamma > Thr)  =  Rate(E_gamma = 0.12 Gev) *K( E_gamma = Thr),
  where k is a calibration coefficient. Note, Rate(E_gamma = 0.12 Gev) is set by the BGRATE parameter;
+
  where K is a calibration coefficient which depends on the photon energy threshold, Thr. The dependence
  it should correspond to 1.1 or 11 GHz of the photon rates for high (10^7 photons/sec) and low
+
of K on the energy threshold is shown in Fig. 1. Note, Rate(E_gamma = 0.12 Gev) is set by the BGRATE  
(10^8 photons/sec) luminosities, respectively.
+
  parameter as has been explained in the previous paragraph.
 +
[[Image:scale_em_rate.jpg|thumb|right|Fig. 1. Scale factor for the EM background rate as function of the  
 +
energy threshold of generated Bremsstrahlung photons. The scale factor equals to 1 at E_gamma = 0.12 GeV]]
 +
 
 +
 
 +
== Headline text ==
 +
 
 +
To study detector responses for electromagnetic background the following MC samples
 +
can be used:
 +
 
 +
* MC sample containing one generated photon per event.
 +
Note, the photon is NOT required to pass throught the collimator into the detector area,
 +
i.e., in most cases it will get stuck in the collimator volumes (the number of photons which
 +
pass throught the collimator is, on average, about a factor of seven less than that produced
 +
for the entire energy spectrum)

Revision as of 14:57, 14 May 2008

This page contains some general descriptions of the generation procedures of electromagnetic background. There are several parameters which has to be set up in the control.in to handle the simulation:

  • BEAM 12. 9.
Electron beam energy and position of the coherent Bremsstrahlung peak.
  • BGRATE 11.0
The rate of background photons in GHz (in the Tagger region before the collimator). 
This parameter should be set either to 1.1 or 11.0 which would correspond to intensities
of the tagged photon beam of 10^7 and 10^8 photons/sec on target, respectively. For 
high-luminosity runs one should use 11.0.
  • BGGATE -50. 50.
Time interval in the ns, the earliest and the latest time, where the background photons are 
produced. This parameters is used to simulate electromagnetic pile-up events.
  • EBREMS_MIN 0.12
The low energy of generated Bremsstrahlung photons. If EBREMS_MIN is commented, or set to 0, 
the default photon-energy threshold of 0.12 GeV is used. If EBREM_MIN is set, the rate of 
generated background photons is automatically scaled as follows:
     Rate(E_gamma > Thr)  =  Rate(E_gamma = 0.12 Gev) *K( E_gamma = Thr),
where K is a calibration coefficient which depends on the photon energy threshold, Thr. The dependence 
of K on the energy threshold is shown in Fig. 1. Note, Rate(E_gamma = 0.12 Gev) is set by the BGRATE 
parameter as has been explained in the previous paragraph.
Fig. 1. Scale factor for the EM background rate as function of the energy threshold of generated Bremsstrahlung photons. The scale factor equals to 1 at E_gamma = 0.12 GeV


Headline text

To study detector responses for electromagnetic background the following MC samples can be used:

  • MC sample containing one generated photon per event.

Note, the photon is NOT required to pass throught the collimator into the detector area, i.e., in most cases it will get stuck in the collimator volumes (the number of photons which pass throught the collimator is, on average, about a factor of seven less than that produced for the entire energy spectrum)