G4InuclSpecialFunctions.cc

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// $Id: G4InuclSpecialFunctions.cc 68163 2013-03-15 20:11:44Z mkelsey $
//
// 20100114  M. Kelsey -- Remove G4CascadeMomentum, use G4LorentzVector directly
// 20100914  M. Kelsey -- Migrate to integer A and Z.  Discard pointless
//              verbosity.
// 20120608  M. Kelsey -- Fix variable-name "shadowing" compiler warnings.
// 20130308  M. Kelsey -- New function to compute INUCL-style random value
// 20130314  M. Kelsey -- Restore null initializer and if-block for _TLS_.
// 20130924  M. Kelsey -- Use G4Log, G4Exp, G4Pow for CPU speedup

#include <cmath>

#include "G4InuclSpecialFunctions.hh"
#include "G4PhysicalConstants.hh"
#include "G4LorentzVector.hh"
#include "G4ThreeVector.hh"
#include "G4Log.hh"
#include "G4Exp.hh"
#include "G4Pow.hh"
#include "Randomize.hh"


// Compute power series in random value, with powers-of-Ekin coeffciences

G4double 
G4InuclSpecialFunctions::randomInuclPowers(G4double ekin, 
                                           const G4double (&coeff)[4][4]) {
  G4Pow* theG4Pow = G4Pow::GetInstance();

  G4double S = G4UniformRand();         // Random fraction for expansion

  G4double C, V;
  G4double PQ=0., PR=0.;
  for (G4int i=0; i<4; i++) {
    V = 0.0;
    for (G4int k=0; k<4; k++) {
      C = coeff[i][k];
      V += C * theG4Pow->powN(ekin, k);
    }

    PQ += V;
    PR += V * theG4Pow->powN(S, i);
  }

  return std::sqrt(S) * (PR + (1-PQ)*(S*S*S*S));
}



G4double G4InuclSpecialFunctions::getAL(G4int A) {
  return 0.76 + 2.2 / G4cbrt(A);
}

G4double G4InuclSpecialFunctions::csNN(G4double e) {
  G4double snn;

  if (e < 40.0) {
    snn = -1174.8 / (e * e) + 3088.5 / e + 5.3107;
  } else {
    snn = 93074.0 / (e * e) - 11.148 / e + 22.429;
  }

  return snn; 
}

G4double G4InuclSpecialFunctions::csPN(G4double e) {
  G4double spn;

  if (e < 40.0) {
    spn = -5057.4 / (e * e) + 9069.2 / e + 6.9466;
  } else {
    spn = 239380.0 / (e * e) + 1802.0 / e + 27.147;
  }

  return spn; 
}

// calculates the nuclei Fermi energy for 0 - neutron and 1 - proton

G4double G4InuclSpecialFunctions::FermiEnergy(G4int A, G4int Z, G4int ntype) {
  const G4double C = 55.4;
  G4double arg = (ntype==0) ? G4double(A-Z)/A : G4double(Z)/A;

  return C * G4cbrt(arg*arg);   // 2/3 power
}

G4double G4InuclSpecialFunctions::G4cbrt(G4double x) {
  return x==0 ? 0. : (x<0?-1.:1.)*G4Exp(G4Log(std::fabs(x))/3.);
}

G4double G4InuclSpecialFunctions::inuclRndm() { 
  return G4UniformRand(); 
} 

G4double G4InuclSpecialFunctions::randomGauss(G4double sigma) {
  const G4double eps = 1.0e-6;
  G4double r1 = inuclRndm();
  r1 = r1 > eps ? r1 : eps;
  G4double r2 = inuclRndm();
  r2 = r2 > eps ? r2 : eps;
  r2 = r2 < 1.0 - eps ? r2 : 1.0 - eps; 

  return sigma * std::sin(twopi * r1) * std::sqrt(-2.0 * G4Log(r2)); 
} 

G4double G4InuclSpecialFunctions::randomPHI() { 
  return twopi * inuclRndm();
} 

std::pair<G4double, G4double> G4InuclSpecialFunctions::randomCOS_SIN() {
  G4double CT = 1.0 - 2.0 * inuclRndm();

  return std::pair<G4double, G4double>(CT, std::sqrt(1.0 - CT*CT));
}

G4LorentzVector 
G4InuclSpecialFunctions::generateWithFixedTheta(G4double ct, G4double p, 
                                                G4double mass) {
  G4double phi = randomPHI();
  G4double pt = p * std::sqrt(std::fabs(1.0 - ct * ct));

  // Buffers to avoid memory thrashing
  static G4ThreadLocal G4ThreeVector *pvec_G4MT_TLS_ = 0;
  if (!pvec_G4MT_TLS_) pvec_G4MT_TLS_ = new G4ThreeVector;
  G4ThreeVector &pvec = *pvec_G4MT_TLS_;

  static G4ThreadLocal G4LorentzVector *momr_G4MT_TLS_ = 0;
  if (!momr_G4MT_TLS_) momr_G4MT_TLS_ = new G4LorentzVector;
  G4LorentzVector &momr = *momr_G4MT_TLS_;

  pvec.set(pt*std::cos(phi), pt*std::sin(phi), p*ct);
  momr.setVectM(pvec, mass);

  return momr;
}

G4LorentzVector 
G4InuclSpecialFunctions::generateWithRandomAngles(G4double p, G4double mass) {
  std::pair<G4double, G4double> COS_SIN = randomCOS_SIN();
  G4double phi = randomPHI();
  G4double pt = p * COS_SIN.second;

  // Buffers to avoid memory thrashing  
  static G4ThreadLocal G4ThreeVector *pvec_G4MT_TLS_ = 0;
  if (!pvec_G4MT_TLS_) pvec_G4MT_TLS_ = new G4ThreeVector;
  G4ThreeVector &pvec = *pvec_G4MT_TLS_;

  static G4ThreadLocal G4LorentzVector *momr_G4MT_TLS_ = 0;
  if (!momr_G4MT_TLS_) momr_G4MT_TLS_ = new G4LorentzVector;
  G4LorentzVector &momr = *momr_G4MT_TLS_;

  pvec.set(pt*std::cos(phi), pt*std::sin(phi), p*COS_SIN.first);
  momr.setVectM(pvec, mass);

  return momr;
}