Problem 1407

Summary:	Cross section of elastic scattering for alpha on water is 0
Product:	Geant4	Reporter:	Yamashita Tomohiro <tomoharo>
Component:	processes/hadronic/cross_sections	Assignee:	dennis.herbert.wright
Status:	RESOLVED WONTFIX
Severity:	normal
Priority:	P5
Version:	9.5
Hardware:	PC
OS:	Linux

Description Yamashita Tomohiro 2012-12-12 07:39:21 CET

I used G4HadronElasticPhysics for elastic scattering in a simulation of alpha (helium ion) on water. The elastic scattering never happened. And it seems it is because G4HadronCrossSections returns 0 for the cross section of the elastic scattering. The interaction length for the process is too big as shown below

G4VDiscreteProcess::PostStepGetPhysicalInteractionLength [ hadElastic]
 Particle type - alpha
   mass:        3.72738[GeV]
   charge:      2[e]
   Direction x: 0, y: 0, z: -1
   Total Momentum = 2.63962[GeV]
   Momentum: 0[GeV], y: 0[GeV], z: -2.63962[GeV]
   Total Energy   = 4.56738[GeV]
   Kinetic Energy = 0.84[GeV]
 MagneticMoment  [MeV/T]: 0
   ProperTime     = 0[ns]
 in Material  G4_WATER
InteractionLength= 1.79769e+307[cm]

Comment 1 dennis.herbert.wright 2013-03-09 01:29:24 CET

Unfortunately, there never has been elastic cross section data for d, t and alpha in Geant4.  Perhaps it was thought that this cross section would be small and it was therefore set to zero.   So while this cross section set is listed as valid for d, t and alpha, it does return zero, by design.

I have added a warning to this effect in the Process/Model catalog on the Geant4 web pages.

If you know of a set of d, t or alpha cross sections for hadronic elastic scattering, please let us know and we can look into adding a new cross section data set.