In Geant4.4.0 and 4.3.2 versions the calculation of neutron life time in hydrogen-content mediums (e.g. water, liguid scintillators, etc.) at room temperature gives the wrong results. The obtained neutron lifetime ~20% lower than the reference values. In Geant4.3.01 version the calculations of neutron lifetime at room temperature is correct. The discrepancy in 4.3.2 and 4.4.0 versions comes from wrong treatement of hydrogen capture libraries. The energy of incident neutron is recalculated, taking into account the temperature movement of Hydrogen atoms. See files G4NeutronHPCapture.cc and G4NeutronHPCapturData.cc. But the hydrogen capture crossection data (GNDL libraries) for thermal neutrons had been measured at room temperature and already take into account the temperature Maxwell distribution of Hydrogen atoms. See for example:"Traite de neutronique", Jean Bussac, ISBN 2 7056 6011 0, 1985, France or other book on neutron physics. The previous version of Geant4 - 4.3.01 gives the correct value of neutron lifetime due to the fact that in files G4NeutronHPCapture.cc and G4NeutronHPCaptureData.cc there were no additional recalculations for temperature movements of medium atoms. Olivier Dadoune dadoun@in2p3.fr Bernard Lefievre lefievre@in2p3.fr Igor Machulin machulin@in2p3.fr
if the G4NDL data are room temperature, we have a bug indeed. It was meant to be at 0K. I'll double-check. Many greetings, Hans-Peter.
Hi folks, I checked, and found that the data are 0K cross-sections. Since this is a 1/v cross-section, though, it is invariant under doppler broadening. In addition, from what I see, the doppler broadening on the fly is effective, but as expected changes the mean cross-section only marginally. Since you see a 20% effect, can you please tell me, what the set-up and data was that you used, to benchmark? Many greetings, Hans-Peter.
a sign error in the calculation of the effective luminosity was fixed in the last neutron_hp tag - neu-V04-00-00 Many greetings, Hans-Peter.
