ReinSehgalRESPXSec.h

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//____________________________________________________________________________
/*!

\class    genie::ReinSehgalRESPXSec

\brief    Computes the double differential cross section for resonance
          electro- or neutrino-production according to the Rein-Sehgal model.

          The computed cross section is the d^2 xsec/ dQ^2 dW \n

          where \n
            \li \c Q^2 : momentum transfer ^ 2
            \li \c W   : invariant mass of the final state hadronic system

          Is a concrete implementation of the XSecAlgorithmI interface.

\ref      D.Rein and L.M.Sehgal, Neutrino Excitation of Baryon Resonances
          and Single Pion Production, Ann.Phys.133, 79 (1981)

\author   Costas Andreopoulos <c.andreopoulos \at cern.ch>
          University of Liverpool

\created  May 05, 2004

\cpright  Copyright (c) 2003-2024, The GENIE Collaboration
          For the full text of the license visit http://copyright.genie-mc.org          
*/
//____________________________________________________________________________

#ifndef _REIN_SEHGAL_RES_PXSEC_H_
#define _REIN_SEHGAL_RES_PXSEC_H_

#include "Framework/EventGen/XSecAlgorithmI.h"
#include "Framework/ParticleData/BaryonResonance.h"
#include "Physics/Resonance/XSection/FKR.h"

namespace genie {

class RSHelicityAmplModelI;
class Spline;
class XSecIntegratorI;

class ReinSehgalRESPXSec : public XSecAlgorithmI {

public:
  ReinSehgalRESPXSec();
  ReinSehgalRESPXSec(string config);
  virtual ~ReinSehgalRESPXSec();

  // implement the XSecAlgorithmI interface
  double XSec         (const Interaction * i, KinePhaseSpace_t k) const;
  double Integral     (const Interaction * i) const;
  bool   ValidProcess (const Interaction * i) const;

  // overload the Algorithm::Configure() methods to load private data
  // members from configuration options
  void Configure(const Registry & config);
  void Configure(string config);

private:

  void LoadConfig (void);

  mutable FKR fFKR;

  const RSHelicityAmplModelI * fHAmplModelCC;
  const RSHelicityAmplModelI * fHAmplModelNCp;
  const RSHelicityAmplModelI * fHAmplModelNCn;
  const RSHelicityAmplModelI * fHAmplModelEMp;
  const RSHelicityAmplModelI * fHAmplModelEMn;

  // configuration data
  bool     fWghtBW;            ///< weight with resonance breit-wigner?
  bool     fNormBW;            ///< normalize resonance breit-wigner to 1?
  double   fZeta;              ///< FKR parameter Zeta
  double   fOmega;             ///< FKR parameter Omega
  double   fMa2;               ///< (axial mass)^2
  double   fMv2;               ///< (vector mass)^2
  double   fSin48w;            ///< sin^4(Weingberg angle)
  double   fVud2;              ///< |Vud|^2(square of magnitude ud-element of CKM-matrix)
  bool     fUsingDisResJoin;   ///< use a DIS/RES joining scheme?
  bool     fUsingNuTauScaling; ///< use NeuGEN nutau xsec reduction factors?
  double   fWcut;              ///< apply DIS/RES joining scheme < Wcut
  double   fN2ResMaxNWidths;   ///< limits allowed phase space for n=2 res
  double   fN0ResMaxNWidths;   ///< limits allowed phase space for n=0 res
  double   fGnResMaxNWidths;   ///< limits allowed phase space for other res
  string fKFTable;             ///< table of Fermi momentum (kF) constants for various nuclei
  bool fUseRFGParametrization; ///< use parametrization for fermi momentum insted of table?
  bool fUsePauliBlocking;      ///< account for Pauli blocking?
  Spline * fNuTauRdSpl;        ///< xsec reduction spline for nu_tau
  Spline * fNuTauBarRdSpl;     ///< xsec reduction spline for nu_tau_bar
  double   fXSecScaleCC;       ///< external CC xsec scaling factor
  double   fXSecScaleNC;       ///< external NC xsec scaling factor
  double   fXSecScaleEM;       ///< external EM xsec scaling factor

  const XSecIntegratorI * fXSecIntegrator;
};

}       // genie namespace

#endif  // _REIN_SEHGAL_RES_PXSEC_H_