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 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
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 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
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 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
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 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/


/////////////////////////////////////////////////////
// Class to handle pairs of tracks of opposite charge
// Useful for resonance analysis
// Derives from AliVParticle => 
// usable in Correction Framework
/////////////////////////////////////////////////////
// author : renaud.vernet@cern.ch
/////////////////////////////////////////////////////


#ifndef ALICFPAIR_H
#define ALICFPAIR_H

#include "AliVParticle.h"

class AliESDtrack ;
class AliESDv0;
class AliESDEvent;

class AliCFPair : public AliVParticle {

 public:
  AliCFPair(AliESDtrack* t1, AliESDtrack* t2);
  AliCFPair(AliESDv0* v0, AliESDEvent* esd);
  AliCFPair(const AliCFPair& c);
  AliCFPair& operator=(const AliCFPair& c);
  virtual ~AliCFPair(){};

  AliESDtrack* GetNeg() const {return fTrackNeg;}
  AliESDtrack* GetPos() const {return fTrackPos;}
  AliESDv0*    GetV0()  const {return fV0;}
  virtual Bool_t       PxPyPz(Double_t p[3]) const ;
  virtual Double32_t   P()  const ;
  virtual Double32_t   Pt() const ;
  virtual Double32_t   Px() const ;
  virtual Double32_t   Py() const ;
  virtual Double32_t   Pz() const ;
  virtual Double32_t   E () const ;
  virtual Double32_t   Xv() const ;
  virtual Double32_t   Yv() const ;
  virtual Double32_t   Zv() const ;
  virtual Bool_t       XvYvZv(Double_t x[3]) const ;

  virtual Double32_t OneOverPt() const {return 1/Pt();}
  virtual Double32_t Phi()   const ;
  virtual Double32_t Theta() const ;
  virtual Double32_t M() const ;
  virtual Double32_t Eta() const ;
  virtual Double32_t Y() const ;
  virtual Short_t    Charge() const {return 0;} // returns 0 because opposite charge tracks... maybe to extend to all kinds of pairs

  // PID
  virtual const Double_t *PID() const {return 0;} // return PID object (to be defined, still)


 private:
  Bool_t fIsV0;            //! true if V0 passed to the constructor
  AliESDtrack* fTrackNeg;  //! pointer to the negative track
  AliESDtrack* fTrackPos;  //! pointer to the positive track
  AliESDv0*    fV0;        //! pointer to the V0 if V0 is passed to the constructor
  
  ClassDef(AliCFPair,0);
};

#endif