Problem 2594

Summary:	Neutrino-nucleus interactions not activated for tau neutrinos
Product:	Geant4	Reporter:	Simon <simon11.thor>
Component:	physics_lists	Assignee:	Vladimir.Ivantchenko
Status:	ASSIGNED ---
Severity:	normal	CC:	Vladimir.Ivantchenko
Priority:	P4
Version:	11.2
Hardware:	All
OS:	All

Description Simon 2024-02-13 17:01:21 CET

In `G4NeutrinoPhysics`, the tau neutrinos do not seem to have any neutrino-nucleus interactions. This is not an issue for muon and electron neutrinos. This is likely caused by a mistake here: https://github.com/Geant4/geant4/blob/master/source/physics_lists/constructors/gamma_lepto_nuclear/src/G4NeutrinoPhysics.cc#L241-L243, which is 
```
  for (G4int i=4; i<=5; ++i) {
    p[i]->GetProcessManager()->AddDiscreteProcess(theNuMuNucleusProcess);
  }
```
Here, `theNuMuNucleusProcess` is added to the tau neutrinos, when `theNuTauNucleusProcess` should be added. This is easily resolved by changing the code to

```
  for (G4int i=4; i<=5; ++i) {
    p[i]->GetProcessManager()->AddDiscreteProcess(theNuTauNucleusProcess);
  }
```

Comment 1 Simon 2024-02-14 11:39:58 CET

Hello,
I tried implementing the change I wrote about in my last comment and recompiled Geant4 but the problem seems to persist. Looking at the source code of https://github.com/Geant4/geant4/blob/master/source/processes/hadronic/cross_sections/src/G4TauNeutrinoNucleusTotXsc.cc, there seem to be several references to the muon neutrino instead of the tau neutrino. Is this intentional or are those also bugs? Do you have any suggestions or workarounds to make tau neutrino-nucleus interactions work in Geant4?