genie::RosenbluthPXSec Class Reference

Differential cross section for charged lepton elastic scattering.
Is a concrete implementation of the XSecAlgorithmI interface.
. More...

#include <RosenbluthPXSec.h>

Inheritance diagram for genie::RosenbluthPXSec:

Public Member Functions
	RosenbluthPXSec ()
	RosenbluthPXSec (string config)
virtual	~RosenbluthPXSec ()
double	XSec (const Interaction *i, KinePhaseSpace_t k) const
	Compute the cross section for the input interaction. More...
double	Integral (const Interaction *i) const
bool	ValidProcess (const Interaction *i) const
	Can this cross section algorithm handle the input process? More...
void	Configure (const Registry &config)
void	Configure (string param_set)
Public Member Functions inherited from genie::XSecAlgorithmI
virtual	~XSecAlgorithmI ()
virtual bool	ValidKinematics (const Interaction *i) const
	Is the input kinematical point a physically allowed one? More...
Public Member Functions inherited from genie::Algorithm
virtual	~Algorithm ()
virtual void	FindConfig (void)
virtual const Registry &	GetConfig (void) const
Registry *	GetOwnedConfig (void)
virtual const AlgId &	Id (void) const
	Get algorithm ID. More...
virtual AlgStatus_t	GetStatus (void) const
	Get algorithm status. More...
virtual bool	AllowReconfig (void) const
virtual AlgCmp_t	Compare (const Algorithm *alg) const
	Compare with input algorithm. More...
virtual void	SetId (const AlgId &id)
	Set algorithm ID. More...
virtual void	SetId (string name, string config)
const Algorithm *	SubAlg (const RgKey &registry_key) const
void	AdoptConfig (void)
void	AdoptSubstructure (void)
virtual void	Print (ostream &stream) const
	Print algorithm info. More...

Private Member Functions
void	LoadConfig (void)

Private Attributes
const XSecIntegratorI *	fXSecIntegrator
const ELFormFactorsModelI *	fElFFModel
ELFormFactors	fELFF
bool	fCleanUpfElFFModel

Additional Inherited Members
Static Public Member Functions inherited from genie::Algorithm
static string	BuildParamVectKey (const std::string &comm_name, unsigned int i)
static string	BuildParamVectSizeKey (const std::string &comm_name)
Protected Member Functions inherited from genie::XSecAlgorithmI
	XSecAlgorithmI ()
	XSecAlgorithmI (string name)
	XSecAlgorithmI (string name, string config)
Protected Member Functions inherited from genie::Algorithm
	Algorithm ()
	Algorithm (string name)
	Algorithm (string name, string config)
void	Initialize (void)
void	DeleteConfig (void)
void	DeleteSubstructure (void)
Registry *	ExtractLocalConfig (const Registry &in) const
Registry *	ExtractLowerConfig (const Registry &in, const string &alg_key) const
	Split an incoming configuration Registry into a block valid for the sub-algo identified by alg_key. More...
template<class T >
bool	GetParam (const RgKey &name, T &p, bool is_top_call=true) const
template<class T >
bool	GetParamDef (const RgKey &name, T &p, const T &def) const
template<class T >
int	GetParamVect (const std::string &comm_name, std::vector< T > &v, bool is_top_call=true) const
	Handle to load vectors of parameters. More...
int	GetParamVectKeys (const std::string &comm_name, std::vector< RgKey > &k, bool is_top_call=true) const
int	AddTopRegistry (Registry *rp, bool owns=true)
	add registry with top priority, also update ownership More...
int	AddLowRegistry (Registry *rp, bool owns=true)
	add registry with lowest priority, also update ownership More...
int	MergeTopRegistry (const Registry &r)
int	AddTopRegisties (const vector< Registry * > &rs, bool owns=false)
	Add registries with top priority, also udated Ownerships. More...
Protected Attributes inherited from genie::Algorithm
bool	fAllowReconfig
bool	fOwnsSubstruc
	true if it owns its substructure (sub-algs,...) More...
AlgId	fID
	algorithm name and configuration set More...
vector< Registry * >	fConfVect
vector< bool >	fOwnerships
	ownership for every registry in fConfVect More...
AlgStatus_t	fStatus
	algorithm execution status More...
AlgMap *	fOwnedSubAlgMp
	local pool for owned sub-algs (taken out of the factory pool) More...

Detailed Description

Differential cross section for charged lepton elastic scattering.
Is a concrete implementation of the XSecAlgorithmI interface.
.

See for example: R.Bradford, A.Bodek, H.Budd, J.Arrington, Nucl.Phys.B159 (2006) 127

Author

Costas Andreopoulos <constantinos.andreopoulos cern.ch> University of Liverpool & STFC Rutherford Appleton Laboratory

Sep 15, 2009

Copyright (c) 2003-2020, The GENIE Collaboration For the full text of the license visit http://copyright.genie-mc.org

Definition at line 32 of file RosenbluthPXSec.h.

Constructor & Destructor Documentation

RosenbluthPXSec::RosenbluthPXSec

(

)

Definition at line 31 of file RosenbluthPXSec.cxx.

                                 :
XSecAlgorithmI("genie::RosenbluthPXSec")
{

}

RosenbluthPXSec::RosenbluthPXSec

(

string

config

)

Definition at line 37 of file RosenbluthPXSec.cxx.

                                              :
XSecAlgorithmI("genie::RosenbluthPXSec", config)
{

}

RosenbluthPXSec::~RosenbluthPXSec ( )

virtual

Definition at line 43 of file RosenbluthPXSec.cxx.

{
  if (fCleanUpfElFFModel) {
    delete fElFFModel;
  }
}

Member Function Documentation

void RosenbluthPXSec::Configure ( const Registry &  config )

virtual

Configure the algorithm with an external registry The registry is merged with the top level registry if it is owned, Otherwise a copy of it is added with the highest priority

Reimplemented from genie::Algorithm.

Definition at line 161 of file RosenbluthPXSec.cxx.

{
  Algorithm::Configure(config);
  this->LoadConfig();
}

void RosenbluthPXSec::Configure ( string  config )

virtual

Configure the algorithm from the AlgoConfigPool based on param_set string given in input An algorithm contains a vector of registries coming from different xml configuration files, which are loaded according a very precise prioriy This methods will load a number registries in order of priority: 1) "Tunable" parameter set from CommonParametes. This is loaded with the highest prioriry and it is designed to be used for tuning procedure Usage not expected from the user. 2) For every string defined in "CommonParame" the corresponding parameter set will be loaded from CommonParameter.xml 3) parameter set specified by the config string and defined in the xml file of the algorithm 4) if config is not "Default" also the Default parameter set from the same xml file will be loaded Effectively this avoids the repetion of a parameter when it is not changed in the requested configuration

Reimplemented from genie::Algorithm.

Definition at line 167 of file RosenbluthPXSec.cxx.

{
  Algorithm::Configure(config);
  this->LoadConfig();
}

double RosenbluthPXSec::Integral ( const Interaction *  i ) const

virtual

Integrate the model over the kinematic phase space available to the input interaction (kinematical cuts can be included)

Implements genie::XSecAlgorithmI.

Definition at line 133 of file RosenbluthPXSec.cxx.

{
  double xsec = fXSecIntegrator->Integrate(this,interaction);
  return xsec;
}

void RosenbluthPXSec::LoadConfig ( void  )

private

Definition at line 173 of file RosenbluthPXSec.cxx.

{
  fElFFModel = 0;

  // load elastic form factors model
  fElFFModel = dynamic_cast<const ELFormFactorsModelI *> ( this -> SubAlg("ElasticFormFactorsModel" ) ) ;

  assert(fElFFModel);

  fCleanUpfElFFModel = false;
  bool useFFTE = false ;
  GetParam( "UseElFFTransverseEnhancement", useFFTE ) ;
  if( useFFTE ) {
    const ELFormFactorsModelI* sub_alg = fElFFModel;
    fElFFModel = dynamic_cast<const ELFormFactorsModelI *> ( this -> SubAlg("TransverseEnhancement") ) ;
    dynamic_cast<const TransverseEnhancementFFModel*>(fElFFModel)->SetElFFBaseModel( sub_alg );
    fCleanUpfElFFModel = true;
  }
  fELFF.SetModel(fElFFModel);

  // load XSec Integrator
  fXSecIntegrator =
      dynamic_cast<const XSecIntegratorI *> (this->SubAlg("XSec-Integrator"));
  assert(fXSecIntegrator);
}

bool RosenbluthPXSec::ValidProcess ( const Interaction *  i ) const

virtual

Can this cross section algorithm handle the input process?

Implements genie::XSecAlgorithmI.

Definition at line 139 of file RosenbluthPXSec.cxx.

{
  if(interaction->TestBit(kISkipProcessChk)) return true;

  const ProcessInfo &  proc_info  = interaction->ProcInfo();

  if(!proc_info.IsQuasiElastic()) return false;
  if(!proc_info.IsEM()) return false;

  const InitialState & init_state = interaction->InitState();

  int  hitnuc = init_state.Tgt().HitNucPdg();
  bool is_pn = (pdg::IsProton(hitnuc) || pdg::IsNeutron(hitnuc));
  if (!is_pn) return false;

  int  probe   = init_state.ProbePdg();
  bool is_chgl = pdg::IsChargedLepton(probe);
  if (!is_chgl) return false;

  return true;
}

double RosenbluthPXSec::XSec ( const Interaction *  i, KinePhaseSpace_t  k  ) const

virtual

Compute the cross section for the input interaction.

Implements genie::XSecAlgorithmI.

Definition at line 50 of file RosenbluthPXSec.cxx.

{
  if(! this -> ValidProcess    (interaction) ) return 0.;
  if(! this -> ValidKinematics (interaction) ) return 0.;

  // Get interaction information
  const InitialState & init_state = interaction -> InitState();
  const Kinematics &   kinematics = interaction -> Kine();
  const Target &       target     = init_state.Tgt();

  int nucpdgc = target.HitNucPdg();
  double E  = init_state.ProbeE(kRfHitNucRest);
  double Q2 = kinematics.Q2();
  double M  = target.HitNucMass();

  double E2 = E*E;
  double E3 = E*E2;
  double M2 = M*M;

  // Calculate scattering angle
  //
  // Q^2 = 4 * E^2 * sin^2 (theta/2) / ( 1 + 2 * (E/M) * sin^2(theta/2) ) =>
  // sin^2 (theta/2) = MQ^2 / (4ME^2 - 2EQ^2)

  double sin2_halftheta = M*Q2 / (4*M*E2 - 2*E*Q2);
  double sin4_halftheta = TMath::Power(sin2_halftheta, 2.);
  double cos2_halftheta = 1.-sin2_halftheta;
  //unused double cos_halftheta  = TMath::Sqrt(cos2_halftheta);
  double tan2_halftheta = sin2_halftheta/cos2_halftheta;

  // Calculate the elastic nucleon form factors
  fELFF.Calculate(interaction);
  double Gm  = pdg::IsProton(nucpdgc) ? fELFF.Gmp() : fELFF.Gmn();
  double Ge  = pdg::IsProton(nucpdgc) ? fELFF.Gep() : fELFF.Gen();
  double Ge2 = Ge*Ge;
  double Gm2 = Gm*Gm;

  // Calculate tau and the virtual photon polarization (epsilon)
  double tau     = Q2/(4*M2);
  double epsilon = 1. / (1. + 2.*(1.+tau)*tan2_halftheta);

  // Calculate the scattered lepton energy
  double Ep  = E / (1. + 2.*(E/M)*sin2_halftheta);
  double Ep2 = Ep*Ep;

  // Calculate the Mott cross section dsigma/dOmega
  double xsec_mott = (0.25 * kAem2 * Ep / E3) * (cos2_halftheta/sin4_halftheta);

  // Calculate the electron-nucleon elastic cross section dsigma/dOmega
  double xsec = xsec_mott * (Ge2 + (tau/epsilon)*Gm2) / (1+tau);

  // Convert dsigma/dOmega --> dsigma/dQ2
  // xsec *= (kPi/(Ep*E)); // bug introduced in v3.0.6
  xsec *= (kPi/(Ep2)); // fixed before v3.2

  // The algorithm computes dxsec/dQ2
  // Check whether variable tranformation is needed
  if(kps!=kPSQ2fE) {
    double J = utils::kinematics::Jacobian(interaction,kPSQ2fE,kps);
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
    LOG("Rosenbluth", pDEBUG)
       << "Jacobian for transformation to: "
       << KinePhaseSpace::AsString(kps) << ", J = " << J;
#endif
    xsec *= J;
  }

  // If requested, return the free nucleon xsec even for input nuclear tgt
  if( interaction->TestBit(kIAssumeFreeNucleon) ) return xsec;

  // Take into account the number of nucleons/tgt
  int NNucl = (pdg::IsProton(nucpdgc)) ? target.Z() : target.N();
  xsec *= NNucl;

  // Compute & apply nuclear suppression factor
  // (R(Q2) is adapted from NeuGEN - see comments therein)
  double R = nuclear::NuclQELXSecSuppression("Default", 0.5, interaction);
  xsec *= R;

  return xsec;
}

Member Data Documentation

bool genie::RosenbluthPXSec::fCleanUpfElFFModel

private

Definition at line 56 of file RosenbluthPXSec.h.

ELFormFactors genie::RosenbluthPXSec::fELFF

mutableprivate

Definition at line 55 of file RosenbluthPXSec.h.

const ELFormFactorsModelI* genie::RosenbluthPXSec::fElFFModel

private

Definition at line 54 of file RosenbluthPXSec.h.

const XSecIntegratorI* genie::RosenbluthPXSec::fXSecIntegrator

private

Definition at line 53 of file RosenbluthPXSec.h.

---

The documentation for this class was generated from the following files:

• Generator/src/Physics/QuasiElastic/XSection/RosenbluthPXSec.h
• Generator/src/Physics/QuasiElastic/XSection/RosenbluthPXSec.cxx