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## Track Momentum Direction

Keywords: Momentum Vector
Forum: Event and Track Management
Date: 18 Mar, 2007
From: Justin Dingley <dinglj@rpi.edu>

 ```Hello all! I have a question regarding the output of the GetMomentumDirection function. I have defined a non-interacting volume in my geometry for tracking bremsstrahlung photon energy and angular distribution. The code snippet below shows how I get the kinetic energy and momentum vector of each photon entering the volume: ....... G4bool CheckVolumeSD::ProcessHits(G4Step* aStep, G4TouchableHistory*) { const G4Track* track = aStep->GetTrack(); if (track->GetDefinition()->GetParticleName() == "gamma") { e = track->GetKineticEnergy(); G4ThreeVector m = track->GetMomentumDirection(); //G4ThreeVector p = track->GetPosition(); mx = m.x(); my = m.y(); mz = m.z(); mm = sqrt(pow(mx,2)+pow(my,2)+pow(mz,2)); angx = acos(mx/mm); angy = acos(my/mm); angz = acos(mz/mm); } return true; } ......... The question I have is about the reference point for the Momentum Vector- is it in relation to the interacting electron vector at the point of photon generation or something else entirely? Thanks in advance, Justin Dingley Rensselaer Polytechnic Nuclear Engineering```

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1 Re: Track Momentum Direction   (Makoto Asai - 18 Mar, 2007)
 to: "Track Momentum Direction"
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