How to add Energy Straggling PhysicsList in a simulation?

i do a simulation using thermal neutron to bomb Boron-10 with thin target of 2e-6 meter, the energy of alpha produced by reaction is scored, the result is below:

as comparation, the result from mcnp and phits are below:
B10_Alpha_Spectrum

it seems no Energy Straggling take place in geant4, how can i add this PhysicsList?

Hello,

by default energy straggling is enabled in Geant4. You may try out FTFP_BERT_HP physics. It is also possible enable thermal neutron physics on top. In your case there may be a problem how forced interaction is enabled.

VI