= bhabha deflection treatment =

guineapig++ can apply beam-beam effect on Bhabha event input file '''bhabha.ini''' ( and eventually '''bhabha_photon.ini''')

internally, bhabhas are considered as being pairs. For activating the bhabha treatment use in '''acc.dat''' the keywords : '''do_bhabhas, track_secondaries, store_secondaries'''. If do_bhabhas = 1 : reads '''bhabha.ini''' only. If do_bhabha = 2 reads '''bhabha_photon.ini''' in addition.




 * '''bhabha.ini''' and '''bhabha_photon.ini''' can be produced with a dedicated bhabha study tool (e.g. [http://hpjmiady.ifj.edu.pl/programs/node1.html BHLUMI]). A bhabha event input is a couple of 4-momenta (in GeV). The format of the file is then : 

{{{
px1 py1 pz1 E1 px2 py2 pz2 E2 
}}}

( index 1 : electrons; index 2 : positrons )

output files are: 

 * '''bhabha_prod.dat''' : bhabhas from file bhabha.ini with additionnal information : a identifier label and 'mother energy'
The format of the file is : 

{{{
label1 motherEnergy1 E1(GeV) px1/E1 py1/E1 pz1/E1
label2 motherEnergy2 E2(GeV) px2/E2 py2/E2 pz2/E2
............................................
}}}

( index 1 : electrons; index 2 : positrons )

 * '''secondaries0.dat''' : 4-momenta of bhabhas '''before tracking''' : 

{{{
 E(GeV) px/E py/E pz/E x y z process id. label 
}}}

(In case of bhabhas, process is '''always -1''' ) 
 
 * '''secondaries.dat''' : same as bhabhas0.dat, but '''after tracking''' 


'''Note''' : for versions ''before'' guineapig++-0.4.0-b the keywords ''track_bhabhas'' and ''store_bhabhas'' are to be used in place of  ''track_secondaries'' and ''store_secondaries''. In a similar way, the output files are not ''secondaries0.dat'' and ''secondaries.dat'' but : ''bhabhas0.dat'' and ''bhabhas.dat'' .