| Summary: | Wrong formula for variance calculation | ||
|---|---|---|---|
| Product: | Geant4 | Reporter: | Konstantin <konstik> |
| Component: | processes/electromagnetic/standard | Assignee: | Vladimir.Ivantchenko |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | ||
| Priority: | P4 | ||
| Version: | 10.7 | ||
| Hardware: | All | ||
| OS: | All | ||
| Attachments: | derivation of the variance formula | ||
Hello, thank you for this bug report. It is fixed and the fix will be available with the next Geant4 public release. In tests, which are used for EM physics validation the effect of the fix is very limited, however in other conditions this fix may be useful. VI |
Created attachment 703 [details] derivation of the variance formula Wrong formula for variance calculation in file /geant4.10.07.p01/source/processes/electromagnetic/standard/src/G4UniversalFluctuation.cc (line 149). Here we have for variance: Var = siga^2 = K*l*Tcut*(1-beta^2/2), where K = 2 * pi * m_e * r_cl^2 * c^2 * n_el * z^2. Instead we should use in this case (see attached file for the derivation of the formula): Var = K*l*Tcut*(1-beta^2/2*Tcut/Tmax).