TUHKMgen/UHKM/StrangeDensity.cxx

   1 #ifndef NAStrangeDensity_h
   2 #include "StrangeDensity.h"
   3 #endif
   4
   5 NAStrangeDensity::NAStrangeDensity():
   6   fTemperature(0.*GeV),
   7   fBaryonPotential(0.*GeV),
   8   fStrangePotential(0.*GeV),
   9   fNMax(5)
  10 {
  11 }
  12 // compute hadron system strangeness density
  13 Double_t NAStrangeDensity::StrangenessDensity(DatabasePDG* database) {
  14   Double_t meanStrangenessDensity = 0.;
  15   for(Int_t particleIndex = 0; particleIndex < database->GetNParticles(); particleIndex++) {
  16     ParticlePDG *particle = database->GetPDGParticleByIndex(particleIndex);
  17     Double_t particleDensity = ParticleNumberDensity(particle);
  18     meanStrangenessDensity += particleDensity*particle->GetStrangeness();
  19   }
  20   return meanStrangenessDensity;
  21 }
  22
  23 // compute hadron number density
  24 Double_t NAStrangeDensity::ParticleNumberDensity(ParticlePDG* pDef) {
  25   Double_t particleMass = pDef->GetMass();
  26   Int_t particleStrangeness = Int_t(pDef->GetStrangeness());
  27   Double_t particleBaryon = pDef->GetBaryonNumber();
  28   //compute chemical potential
  29   Double_t particleChemPotential = fBaryonPotential*particleBaryon +
  30                                    fStrangePotential*particleStrangeness;
  31   //compute degeneracy factor
  32   Double_t particleDegFactor = 2*pDef->GetSpin() + 1.;     // IA: In ParticlePDG() GetSpin() returns spin not 2*spin !!
  33   Double_t d = 1.;//for fermions
  34   if(Int_t(2*pDef->GetSpin())%2 == 0)//it gives 0 for Spin = 0,2,4,.. and it gives 1 for Spin = 1,3,7,
  35     d = -1; //for bosons
  36
  37   Double_t prefactor;
  38   Double_t postfactor;
  39   prefactor = (particleDegFactor*particleMass*particleMass*
  40                fTemperature/hbarc/hbarc/hbarc)/(2.*N_PI*N_PI);
  41   postfactor = 0.;
  42
  43   for(Int_t n = 1; n <= fNMax; n++) {
  44     postfactor += pow(-d,n+1)/(n)*exp(n*particleChemPotential/fTemperature)*
  45       HankelKn(2,n*particleMass/fTemperature);
  46   }
  47   return prefactor*postfactor;
  48 }
  49