StNegativeBinomial.h

/******************************************************************************
 * $Id: StNegativeBinomial.h,v 1.2 2012/04/25 05:13:24 hmasui Exp $
 * $Log: StNegativeBinomial.h,v $
 * Revision 1.2  2012/04/25 05:13:24  hmasui
 * Use STAR logger. Take into account additional constant inefficiency by using the trigger bias parameter
 *
******************************************************************************/

#ifndef __StNegativeBinomial_h__
#define __StNegativeBinomial_h__

class TH1 ;
#include "Rtypes.h"

//____________________________________________________________________________________________________
//  StNegativeBinomial class: Generate negative binomial distribution
class StNegativeBinomial {
  public:
    //  npp: mean multiplicity in p+p
    //  k:   1/k deviation from poisson (1/k -> 0 poisson)
    //  x:   fraction of hard component
    //  efficiency: detector efficiency
    //  triggerbias: trigger bias
    //  IsConstEfficiency: true-> constant efficiencty, false-> multiplicity dependent efficiency
    StNegativeBinomial(const Double_t npp = 2.38, const Double_t k = 2.00, const Double_t x = 0.13,
        const Double_t efficiency = 1.0, const Double_t triggerbias = 1.0, const Bool_t isConstEfficiency=kTRUE);

    virtual ~StNegativeBinomial();

    Double_t GetTwoComponentMultiplicity(const Double_t npart, const Double_t ncoll) const ;

    Int_t GetMultiplicity(const Double_t npart, const Double_t ncoll) const ;

    TH1* GetMultiplicity(const Double_t npart, const Double_t ncoll,
        const Double_t weight) const ;

    Double_t GetNegativeBinomial(const Int_t n) const ; 
    Double_t GetNegativeBinomial(const Int_t n, const Double_t m) const ; 

    void SetParameters(const Double_t npp, const Double_t k, const Double_t x = -1.0)  ;

    // Getter
    Double_t GetNpp() const ; 
    Double_t GetK()   const ; 
    Double_t GetX()   const ; 
    Double_t GetEfficiency() const ; 
    Bool_t IsConstEfficiency()   const ; 
    void DrawNbd() const ;    

  private:
    // Functions
    Double_t GetEfficiency(const Int_t mult) const ;
    void InitHistogram() ; 

    // Data members
    const Double_t mEfficiency      ; 
    const Double_t mTriggerBias     ; 
    Double_t mNpp                   ; 
    Double_t mK                     ; 
    Double_t mX                     ; 
    const Bool_t mIsConstEfficiency ; 
    static UInt_t mCounter          ; 

    TH1* mhNbd    ; 

    ClassDef(StNegativeBinomial, 0)
};

inline Double_t StNegativeBinomial::GetNpp() const { return mNpp ; }
inline Double_t StNegativeBinomial::GetK()  const { return mK ; }
inline Double_t StNegativeBinomial::GetX()  const { return mX ; }
inline Double_t StNegativeBinomial::GetEfficiency() const { return mEfficiency ; }
inline Bool_t StNegativeBinomial::IsConstEfficiency() const { return mIsConstEfficiency ; }

#endif