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Forum: Hadronic Processes
Re: None Tachyonic Particle Problem- Geant4 V 9.3- Ultra High Energy QGSP (Tomasz Sakrejda)
Re: None Re: Tachyonic Particle Problem- Geant4 V 9.3- Ultra High Energy QGSP (Dennis H. Wright)
Date: 08 Mar, 2011
From: Tomasz Sakrejda <Tomasz Sakrejda>

Let me know if I should really hand this over to Vladimir? I'm still not sure because it's a problem with QGSP it seems.

Worked on it some more. I've narrowed the energy range where it occurs down to between 90 and 100 PeV. At 90 PeV, >95% of the runs DO NOT have this problem. (I ran 1000 events and it crashed on the 954th-)

At 100 PeV, it crashes much, much, much more often. I tried four different random seeds and they all gave the tachyonic error. Furthermore, the error is extremely strange- all of the runs crashed on nearly the same step! They crashed at different positions and different step/tracklengths/changes in energy. The process is always the same- hioni. I have a suspicion that the energies of the protons might cross some threshold and that's what causes the problem, but I can't see the energy with sufficient precision and I'm not sure how to get Geant4 to give that information without implementing a TrackingAction class. Here's what I mean:

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
  259 0.000111 -3.2e-05      657     1e+11  0.00262     19.2  5.07e+04      Target hIoni
  259 3.94e-05 8.64e-05 3.46e+03     1e+11    0.014     72.6  5.35e+04      Target hIoni
  260 4.24e-05 3.32e-05 3.48e+03     1e+11  0.00561     12.1  5.35e+04      Target hIoni

My macro is the same as before up to the change in energy, and the inclusion of a setSeeds command.

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1 Idea: Re: Tachyonic Particle Problem- Geant4 V 9.3- Ultra High Energy QGSP   (Vladimir Ivanchenko - 09 Mar, 2011)
(_ None: Re: Tachyonic Particle Problem- Geant4 V 9.3- Ultra High Energy QGSP   (Tomasz Sakrejda - 09 Mar, 2011)
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