G4InuclParamMomDst.cc

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// $Id: G4InuclParamMomDst.cc 67863 2013-03-11 19:00:21Z mkelsey $
// Author:  Michael Kelsey (SLAC)
// Date:    7 March 2013
//
// Description: intermediate base class for INUCL parametrizations of
//      final-state momentum distributions in Bertini-style cascade
//
// 20130308  M. Kelsey -- Move PQ,PR calculation to G4InuclSpecialFunctions.
// 20130924  M. Kelsey -- Replace std::pow with G4Pow::powN() for CPU speed

#include "G4InuclParamMomDst.hh"
#include "G4InuclSpecialFunctions.hh"
#include "G4InuclParticleNames.hh"
#include "G4Pow.hh"
#include "Randomize.hh"

using namespace G4InuclSpecialFunctions;
using namespace G4InuclParticleNames;


// Use coefficients in power expansion of random fraction

G4double 
G4InuclParamMomDst::GetMomentum(G4int ptype, const G4double& ekin) const {
  if (verboseLevel>3) {
    G4cout << theName << "::GetMomentum: ptype " << ptype << " ekin " << ekin
       << G4endl;
  }

  G4int JK = (ptype==pro || ptype==neu) ? 0 : 1;    // nucleon vs. other

  if (verboseLevel > 3) G4cout << " JK " << JK << G4endl;

  G4Pow* theG4Pow = G4Pow::GetInstance();   // For convenience

  G4double Spow = randomInuclPowers(ekin, coeffPR[JK]);

  G4double C=0., PS=0.;
  for(G4int im = 0; im < 3; im++) {
    C = coeffPS[JK][im];
    PS += C * theG4Pow->powN(ekin, im);

    if (verboseLevel >3) {
      G4cout << " im " << im << " : coeffPS[JK][im] " << C
         << " ekin^im " << theG4Pow->powN(ekin, im) << G4endl;
    }
  }
  
  G4double PRA = PS * Spow;

  if (verboseLevel > 3) 
    G4cout << " PS " << PS << " Spow = sqrt(S)*(PR+(1-PQ)*S^4) " << Spow
       << " PRA = PS*Spow " << PRA << G4endl;

  return std::fabs(PRA);
}