impact_parameter_distribution.h

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#ifndef __KVSMOOTHIPDIST_H
#define __KVSMOOTHIPDIST_H
 
#include "KVBase.h"
#include "TF1.h"
 
namespace KVImpactParameters {
   class impact_parameter_distribution : public KVBase {
 
   private:
      TH1*  fHisto;
      TF1 fIPdist;
      TF1 fSigmaR;
      TF1 fCentrality;
 
   public:
      impact_parameter_distribution();
      impact_parameter_distribution(TH1*);
      virtual ~impact_parameter_distribution() {}
 
      void FitIPDist(TH1*);
 
      Double_t GetCrossSection() const;
      Double_t GetB0() const
      {
         return fIPdist.GetParameter(1);
      }
      Double_t GetDeltaB() const
      {
         return fIPdist.GetParameter(2);
      }
      Double_t GetCrossSectionPerEvent() const;
      void SetB0(Double_t x)
      {
         fIPdist.SetParameter(1, x);
         fCentrality.SetParameter(0, x);
      }
      void SetDeltaB(Double_t x)
      {
         fIPdist.SetParameter(2, x);
         fSigmaR.SetParameter(0, x);
         fCentrality.SetParameter(1, x);
      }
      void SetDeltaB_WithConstantCrossSection(Double_t deltab, Double_t sigmaR = 0);
      TF1& GetIPDist()
      {
         return fIPdist;
      }
      void Draw(Option_t* opt = "")
      {
         fIPdist.Draw(opt);
      }
      const TF1& GetSigmaR()
      {
         return fSigmaR;
      }
      const TF1& GetCentrality()
      {
         return fCentrality;
      }
      Double_t Calculate_b(Double_t centrality) const;
 
      void NormalizeIPDistToCrossSection()
      {
 
         fIPdist.SetParameter(0, 10.*TMath::TwoPi() / GetCrossSection());
      }
 
      Double_t GetRelativeCrossSection(double b) const
      {
         if (b > 0) return fIPdist.Eval(b) / (b * fIPdist.GetParameter(0));
         return 0;
      }
 
      Double_t GetDifferentialCrossSection(double b) const
      {
 
         if (b > 0) {
            return fIPdist.Eval(b) / fIPdist.GetParameter(0) * 10 * TMath::TwoPi();
         }
         return 0;
      }
      void MakeDifferentialCrossSection()
      {
         fIPdist.SetParameter(0, 10 * TMath::TwoPi());
      }
 
      ClassDef(impact_parameter_distribution, 1) //Realistic impact parameter distribution with smooth fall-off at large b
   };
}
#endif