Re: [ROOT] TPythia problems

From: joseph.tuggle@tufts.edu
Date: Fri Jul 26 2002 - 23:40:26 MEST


Thanks Rene -- I ended up switching to TPythia6, and that was a lot
easier to use. I guess it handles the particle list on its own so I
don't have to mess around with it.

Thanks!
Joe

Quoting Rene Brun <brun@pcbrun.cern.ch>:

> Hi Joe,
> 
> By default, TPythia::GenerateEvent produces TMCParticle not TParticle.
> See example below to access the TPCParticle data.
> 
> Rene Brun
> 
> {
>    // dynamically link the shared libraries
>    gSystem->Load("$PYTHIA/libPythia.so");  // Pythia library
>    gSystem->Load("libEG.so");              // Root Event Generator
> interface
>    gSystem->Load("libEGPythia.so");        // Root interface to Pythia
> 
>    TPythia *myPythia = new TPythia();
>    TMCParticle *myParticle;
> 
>    // Assume I've completed all initialization
> 
>    myPythia->Initialize("CMS","p","p",14000);
>    myPythia.GenerateEvent();
>    int numParticles = myPythia.GetNumberOfParticles();
>    TObjArray *particles = myPythia.GetListOfParticles();
>    for(int i = 0; i < numParticles; i++) {
>       myParticle = (TMCParticle*)particles->At(i);
>       int KS   = myParticle->GetKS();
>       float px = myParticle->GetPx();
>       float py = myParticle->GetPy();
>       float pz = myParticle->GetPz();
>       printf("i=%4d, KS=%d, px=%g, py=%g, pz=%g\n",i,KS,px,py,pz);
>    }
> }
> 
> 
> On Fri, 26 Jul 2002, Joseph Tuggle wrote:
> 
> > Hi,
> > 
> > When I use the TPythia class to generate events, I seem to get 
> > uninitialized variables instead of actual values. Here is an
> example...
> > 
> > TPythia myPythia;
> > TParticle *myParticle;
> > 
> > // Assume I've completed all initialization
> > 
> > myPythia.GenerateEvent();
> > int numParticles = myPythia.GetNumberOfParticles();
> > for(int i = 0; i < numParticles; i++) {
> >   myParticle = myPythia.GetParticle(i);
> >   float px = myParticle->Px();
> > }
> > 
> > Now, if I look at px, py, pz, etc, they all seem to be uninitialized.
> 
> > Same for Vx, Vy, Vz, and so on. Is there something simple I'm
> missing?
> > 
> > Thanks,
> > Joe
> > 
> > 
> 
> 



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