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