Problem 1719

Summary: Bug in Zeff computation for sampling calorimeters
Product: Geant4 Reporter: aferrero19752
Component: parameterisations/gflashAssignee: Marc.Verderi
Status: ASSIGNED ---    
Severity: major CC: aferrero19752
Priority: P5    
Version: 10.1   
Hardware: All   
OS: All   

Description aferrero19752 2015-03-10 10:46:01 CET 
I've recently started to look into the gflash code and I'm comparing results obtained with geant4 and the original fortran GFlash code.

While doing that, I've noticed that the computation of the effective Z for sampling calorimeters looks suspicious:

  Zeff   = ( W1*Z2 ) + (W2*Z1);    //X0*Es/Ec;
  Aeff   = ( W1*A1 ) + (W2*A2);


My impression is that Z1 and Z2 are swapped in the computation of Zeff. Since Zeff enters in several formulas for the computation of the longitudinal ad transverse shower shapes, I think this bug (if confirmed) could have a major impact on the simulation.


The suspicious line appears in 
source/parameterisations/gflash/src/GFlashSamplingShowerParameterisation.cc
Comment 1 Marc.Verderi 2015-10-02 12:50:57 CEST 
Sorry for the (so) long silence on this.

I agree the Z1 and Z2 are swapped.

The bug report is kept open for now, while making validations.