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News Re: Primary Vertex Information to Track Information, and question about multiple parent tracks 

Forum: Event and Track Management
Re: Question Primary Vertex Information to Track Information, and question about multiple parent tracks (Young)
Date: 10 Aug, 2013
From: Michael H. Kelsey <Michael H. Kelsey>

On Fri, 09 Aug 2013 22:04:24 GMT, Young wrote:
> I am currently running a calorimeter simulation in Geant4 using HepMC
> event records as the input. (The HepMC event record is produced by a
> Pythia generator, separate to my simulation.)
> 
> My goal is to record which HepMC GenParticle each track originated from.
> As far as I can tell, I could modify the existing PrimaryTransformer
> class (and the EventManager class), so that it takes
> UserPrimaryVertexInformation and converts it into UserTrackInformation,
> attaching it to the corresponding produced tracks. Is there a better way
> to do this?
> 
> My second question is regarding the ParentID of a track that is produced
> at the interaction vertex of two or more particles, for example e+e-
> annihilation. For each of the two gammas produced by e+e- annihilation,
> you could consider either the e+ or the e- track as the "parent track".
> How does Geant4 decide which track to assign the gamma track? In other
> words, if I called the GetParentID() method for one of the gamma tracks,
> which TrackID would it return, the e+ or the e-?

GEANT4 does not support direct interaction between tracks. You cannot do event generation with colliding beams using GEANT4 -- you have to use some other event generator program for that.

The case of positron annihilation arises (in GEANT4) only in the context of a positron track interacting with an atom (i.e., one of the orbital electrons). In that case, the gammas are unambigously assigned as daughters of the positron.

  -- Michael Kelsey

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1 None: Re: Primary Vertex Information to Track Information, and question about multiple parent tracks   (Young - 11 Aug, 2013)
1 Idea: Re: Primary Vertex Information to Track Information, and question about multiple parent tracks   (Gumplinger Peter - 15 Aug, 2013)
2 None: Re: Primary Vertex Information to Track Information, and question about multiple parent tracks   (Marek Szuba - 19 Aug, 2013)
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