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Electromagnetic background



Dear Colleagues,

I've introduced a new parameter in the control.in file,
EBREM_MIN, which allows one to set a threshold on the low
energy of the generated bremsstrahlung photons (which is
related to the  electromagnetic background studies)
As an example,
 EBREM_MIN  0.0012
sets a threshold of the photon energy to 0.0012 GeV.

If  EBREMS_MIN  is commented, or set to 0, the default
photon-energy  threshold of 0.12 GeV  is used. If the EBREM_MIN
card is set, the rate of background photons is automatically
scaled as follows:
Rate(E_gamma > Thr)  =  Rate(E_gamma > 0.12 Gev) * K,
where K is the scale factor calculated inside the program:
K = 1 for Thr = 0.12 GeV, K > 1 for Thr < 0.12 GeV.
Rate(E_gamma > 0.12 Gev) corresponds to 1.1 GHz and 11 GHz
for low-luminosity (10^7 phot/sec) and high-luminosity
(10^8 phot/sec) runs, respectively.
Note, K is calculated assuming that a beam energy card is set
to BEAM 12. 9.


To be able to use EBREMS_MIN parameter, you have to update
beamgen.F, uginit.F, and control in files from a repository
(HDGeant directory) and recompile hdgeant.

----------

As promised, I also put some very simple examples on the
electromagnetic background simulation to the wiki offline
software "HOWTO" page
http://www.jlab.org/Hall-D/software/wiki/index.php/Offline_Software
"HOWTO to generate electromagnetic background"


Cheers,
       Sascha