G4NumIntTwoBodyAngDst.icc

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// $Id: G4NumIntTwoBodyAngDst.icc 71719 2013-06-21 00:01:54Z mkelsey $
// Author:  Dennis Wright (SLAC)
// Date:    28 January 2013
//
// Description: implementation base for numerically integrated two-body
//              final state angular distributions in Bertini-style cascade
//
// 20130219        M. Kelsey: Move to .icc file, required for templated classes
// 20130620  Fix Coverity #50295, recursive #include.
// 20130924  M. Kelsey -- Use G4Log, G4Exp for CPU speedup

#ifndef G4NumIntTwoBodyAngDst_icc
#define G4NumIntTwoBodyAngDst_icc 1

#include "G4Log.hh"
#include "G4Exp.hh"
#include "Randomize.hh"


template <G4int NKEBINS, G4int NANGLES> G4double
G4NumIntTwoBodyAngDst<NKEBINS,NANGLES>::
GetCosTheta(const G4double& ekin, const G4double& pcm) const
{
  G4double costh=1.0, slope=1.0;           // Buffers for final result
  G4double xrand = G4UniformRand();                // Random value to sample CDF

  if (ekin < labKE[nDists-1]) {
    Interpolate(ekin);                             // Get intermediate CDF @ energy
    for (G4int i=1; i<nAngles; i++) {
      if (xrand < angDist[i]) {
        slope = (cosBins[i] - cosBins[i-1])/(angDist[i] - angDist[i-1]);
        costh = (xrand - angDist[i-1])*slope + cosBins[i-1];
        break;
      }
    }
  } else {
    slope = 2.*tcoeff*pcm*pcm; 
    costh = G4Log(1.0 - xrand*(1. - G4Exp(2.*slope) ) )/slope - 1.0;
  }
  return costh;
}


// Find normalized indefinite integral of angular distribution at interpolated
// kinetic energy

template <G4int NKEBINS, G4int NANGLES>
void G4NumIntTwoBodyAngDst<NKEBINS,NANGLES>::Interpolate(const G4double& ekin) const
{
  for (G4int j=1; j<nDists; j++) {
    if (ekin >= labKE[j]) continue;        // Find desired pair of cos(theta) CDFs

    G4double frac = (ekin - labKE[j-1])/(labKE[j] - labKE[j-1]);
    for (G4int i=0; i < nAngles; i++) {
      angDist[i] = (1.0 - frac)*angDists[j-1][i] + frac*angDists[j][i];
    }

    break;
  }
}

#endif     /* G4NumIntTwoBodyAngDst_icc */