RSHelicityAmpl.h

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//____________________________________________________________________________
/*!
 
\class    genie::RSHelicityAmpl
 
\brief    A class holding the Rein-Sehgal's helicity amplitudes.
 
          This class is using the \b Strategy Pattern. \n
          It can accept requests to calculate itself, for a given interaction,
          that it then delegates to the algorithmic object, implementing the
          RSHelicityAmplModelI interface, that it finds attached to itself.
 
\author   Costas Andreopoulos <c.andreopoulos \at cern.ch>
          University of Liverpool
 
\created  May 03, 2004
 
\cpright  Copyright (c) 2003-2025, The GENIE Collaboration
          For the full text of the license visit http://copyright.genie-mc.org          
*/
//____________________________________________________________________________
 
#ifndef _RS_HELICITY_AMPL_H_
#define _RS_HELICITY_AMPL_H_
 
#include <iostream>
 
#include <TMath.h>
 
#include "Framework/Interaction/Interaction.h"
#include "Physics/Resonance/XSection/FKR.h"
 
using std::ostream;
 
namespace genie {
 
class RSHelicityAmpl;
ostream & operator<< (ostream & stream, const RSHelicityAmpl & hamp);
 
class RSHelicityAmpl {
 
friend class RSHelicityAmplModelCC;
friend class RSHelicityAmplModelNCp;
friend class RSHelicityAmplModelNCn;
friend class RSHelicityAmplModelEMp;
friend class RSHelicityAmplModelEMn;
 
public:
 
  RSHelicityAmpl();
  RSHelicityAmpl(const RSHelicityAmpl & hamp);
  ~RSHelicityAmpl() { }
 
  //! return helicity amplitude
  double AmpMinus1 (void) const  { return fMinus1; } /* f(-1) */
  double AmpPlus1  (void) const  { return fPlus1;  } /* f(+1) */
  double AmpMinus3 (void) const  { return fMinus3; } /* f(-3) */
  double AmpPlus3  (void) const  { return fPlus3;  } /* f(+3) */
  double Amp0Minus (void) const  { return f0Minus; } /* f(0-) */
  double Amp0Plus  (void) const  { return f0Plus;  } /* f(0+) */
 
  //! return |helicity amplitude|^2
  double Amp2Minus1 (void) const { return TMath::Power(fMinus1, 2.); } /* |f(-1)|^2 */
  double Amp2Plus1  (void) const { return TMath::Power(fPlus1,  2.); } /* |f(+1)|^2 */
  double Amp2Minus3 (void) const { return TMath::Power(fMinus3, 2.); } /* |f(-3)|^2 */
  double Amp2Plus3  (void) const { return TMath::Power(fPlus3,  2.); } /* |f(+3)|^2 */
  double Amp20Minus (void) const { return TMath::Power(f0Minus, 2.); } /* |f(0-)|^2 */
  double Amp20Plus  (void) const { return TMath::Power(f0Plus,  2.); } /* |f(0+)|^2 */
 
  friend ostream & operator<< (ostream & stream, const RSHelicityAmpl & hamp);
 
  void Print(ostream & stream) const;
 
private:
 
  void   Init(void);
 
  double fMinus1;
  double fPlus1;
  double fMinus3;
  double fPlus3;
  double f0Minus;
  double f0Plus;
};
 
}        // genie namespace
 
#endif   // _RS_HELICITY_AMPL_H_