Physics Lists for low energy antiprotons

Particles, Track, Event, Run and Biasing
1

Geant4 Version: 10.7.2
Operating System: Ubuntu 20.04.6 LTS
Compiler/Version: gcc (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0
CMake Version: cmake version 3.16.3

Hello everyone,

I am using Geant4 to strike low energy (8 keV) antiprotons on an aluminum detector but somehow my antiproton beam in not penetrating the surface of this detector. When I tried to increase the energy of the antiproton beam (around 2 MeV), it got reflected from the surface.

I am using below mentioned physics lists for this.
RegisterPhysics(new G4EmStandardPhysics());
RegisterPhysics(new G4HadronPhysicsFTFP_BERT());
RegisterPhysics(new G4DecayPhysics());
RegisterPhysics(new G4HadronPhysicsINCLXX());
RegisterPhysics(new G4EmStandardPhysics_option4());

Kindly help me regarding this issue.

Thanks in advance