diff --git a/src/detector_sim.cpp b/src/detector_sim.cpp
index 8032267f2929e039c89f01cc63331c6690b32489..782393694724afcff2b817b1e372a7437ebf93ac 100644
--- a/src/detector_sim.cpp
+++ b/src/detector_sim.cpp
@@ -244,6 +244,9 @@ int main(int argc, char **argv){
       TMatrixD Rot2 = TMatrixD(3,3,rot2);
       TMatrixD Rot2Inv(TMatrixD::kInverted,Rot2);
       
+      //actually not necessary to calculate the momentum vector in the rotated
+      //coordiante system, since it is anyway along the z axis, but let's do it
+      //anyway
       TVectorD p_rot = Rot2*Rot1*temp_state->GetMomentum();
       
       //Rotate the momentum vector due to multiple scattering