Re: GEANT Branching Fraction Table

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Thu, 31 Jul 2008, Alexander Somov wrote:

Dear Matt et all,

why do you want Geant let the eta or pi0 decay.
Pythia can do this for you as well,
You need to put for the pi
mdcy(pycomp(211),1)=1

if you do
call pylist(12)
you get a list of all decays included.

Of course geant works as well, but to do it in pythia might be easier.

cheers elke




> Date: Thu, 31 Jul 2008 17:46:55 -0400 (EDT)
> From: Alexander Somov <somov@jlab.org>
> To: Matthew Shepherd <mashephe@indiana.edu>
> Cc: GlueX Software <halld-offline@jlab.org>
> Subject: Re: GEANT Branching Fraction Table
>
>
> You have to recompile HDGeant (, i.e., parameters should be hardcoded).
> You can overwrite the branching fractions in the uginit.F file
> (in the Simulation/HDGeant directory) where geant is initialized:
>
>       integer my_ipart
>       real    my_bratio(6)
>       integer my_mode(6)
>
>       data my_bratio/0.0,0.0,0.0,0.0,0.0,0.0/
>       data my_mode/0,0,0,0,0,0/
>
>       ......
>
> *             Initialize GEANT tracking structures
> *
> C..geant..
> C     eta - > gamma gamma
>       my_mode(1)   = 10100
> C     Br = 100%
>       my_bratio(1) = 100.0
>       CALL GSDK(17,my_bratio,my_mode)
> C     number 17 stands for eta
>
> ---------------------------------
>
> Then, make.
>
>
> When you start hdgeant you should get the message:
>  *** GSDK ***: Warning, redefinition of decay for particle:
> 0Part                         Options        Mass    Charge    Life time      User words
>
>    17 ETA                        3       0.5475E+00     0.    0.54850E-18
>
>
>
> I've just generetaed a few events with eta's. It's forced to decay into 2
> gammas. See also some details in the www page I've sent to you in my last
> mail.
>
> Cheers,
>        Sascha
>
>
>
>
>
>
>
>
> On Thu, 31 Jul 2008, Matthew Shepherd wrote:
>
> >
> > Sascha,
> >
> > Thanks -- yes, for PYTHIA, just the eta itself is passed onto GEANT.
> > Do you know how to override the default decay branching fractions in
> > the code?
> >
> > I see that (unfortunately) GEANT has builtin a non-zero branching
> > fraction for eta -> pi^0 gamma gamma which one of the rare signal
> > mdoes that Liping is interested in.
> >
> > -Matt
> >
> >
> > On Jul 31, 2008, at 3:07 PM, Alexander Somov wrote:
> >
> > >
> > > http://wwwasdoc.web.cern.ch/wwwasdoc/geant_html3/node73.html#DRAW001
> > > (the same table is in geant 3.21 manual)
> > >
> > > (I am not sure that your eta decays in geant; it might decay
> > > in the event generator directly (?))
> > >
> > > Sascha
> > >
> > >
> > > On Thu, 31 Jul 2008, Matthew Shepherd wrote:
> > >
> > >>
> > >> Hi,
> > >>
> > >> Can anyone tell me where the branching fraction table for eta's is
> > >> coded into GEANT3?
> > >>
> > >> Thanks!
> > >>
> > >> -Matt
> > >>
> > >>
> > >
> >
> >
>
>

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