Changed absorption chance calculation to reflect the terminology

MonteCarlo/src/FiberSD.cc

@@ -176,8 +176,8 @@ G4bool FiberSD::ProcessHits(G4Step* aStep,G4TouchableHistory*){
             G4ThreeVector momDir = aStep->GetPreStepPoint()->GetMomentumDirection();
             //pathLength =  (distance to top of fiber)/sin(polarAngle); polarAngle = atan(y/sqrt(x^2 + z^2));
             G4double pathLength = (m_topOfVolume - pos.y())/sin( atan(momDir.y()/sqrt( pow(momDir.x(),2.0) + pow(momDir.z(),2.0) ) ) );
-            G4double absChance = exp(-pathLength/Absorption);
-            if(CLHEP::RandFlat::shoot(0.0,1.0) < absChance){//This check amounts to if(!absorbed)
+            G4double absChance = 1 - exp(-pathLength/Absorption);
+            if(CLHEP::RandFlat::shoot(0.0,1.0) > absChance){//This check amounts to if(!absorbed)
               //Finally, record the ouput
               if(REDUCED_TREE){
                 m_cherenkovVec->at(rodNum)++;