genie::PaisQELLambdaPXSec Class Reference

Implementation of the quasi-elastic scattering formula for production of particles with different masses than the target. More...

#include <PaisQELLambdaPXSec.h>

Inheritance diagram for genie::PaisQELLambdaPXSec:

Public Member Functions
	PaisQELLambdaPXSec ()
	PaisQELLambdaPXSec (string config)
virtual	~PaisQELLambdaPXSec ()
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...
bool	ValidKinematics (const Interaction *i) const
	Is the input kinematical point a physically allowed one? More...
void	Configure (const Registry &config)
void	Configure (string param_set)
Public Member Functions inherited from genie::XSecAlgorithmI
virtual	~XSecAlgorithmI ()
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)
double	MHyperon (const Interaction *interaction) const

Private Attributes
QELFormFactors	fFormFactors
const QELFormFactorsModelI *	fFormFactorsModel
const XSecIntegratorI *	fXSecIntegrator
double	fSin8c2

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

Implementation of the quasi-elastic scattering formula for production of particles with different masses than the target.

Weak Interactions at High Energies A. Pais, Annals of Physics 63, 361-392 (1971) Implemented here is equation 2.34 of the Pais paper, but ignoring lepton mass terms. This equation is given also as Equation 3.37 in the Llewellyn-Smith paper, though this paper uses slightly different notation than that used in the Pais paper, and introduces a small error in the kinematic coefficient of the w2 term. The notation here by and large follows that of the Llewelyn-Smith paper.

Author

Hugh Gallagher Tufts University

June 10, 2004

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

Definition at line 39 of file PaisQELLambdaPXSec.h.

Constructor & Destructor Documentation

PaisQELLambdaPXSec::PaisQELLambdaPXSec

(

)

Definition at line 37 of file PaisQELLambdaPXSec.cxx.

                                       :
XSecAlgorithmI("genie::PaisQELLambdaPXSec")
{

}

PaisQELLambdaPXSec::PaisQELLambdaPXSec

(

string

config

)

Definition at line 43 of file PaisQELLambdaPXSec.cxx.

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

}

PaisQELLambdaPXSec::~PaisQELLambdaPXSec ( )

virtual

Definition at line 49 of file PaisQELLambdaPXSec.cxx.

{

}

Member Function Documentation

void PaisQELLambdaPXSec::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 208 of file PaisQELLambdaPXSec.cxx.

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

void PaisQELLambdaPXSec::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 214 of file PaisQELLambdaPXSec.cxx.

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

double PaisQELLambdaPXSec::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 145 of file PaisQELLambdaPXSec.cxx.

{

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

void PaisQELLambdaPXSec::LoadConfig ( void  )

private

Definition at line 220 of file PaisQELLambdaPXSec.cxx.

{

  double thc ;
  GetParam( "CabibboAngle", thc ) ;
  fSin8c2 = TMath::Power(TMath::Sin(thc), 2);

  // load QEL form factors model
  fFormFactorsModel = dynamic_cast<const QELFormFactorsModelI *> (
                                             this->SubAlg("FormFactorsAlg"));
  assert(fFormFactorsModel);
  fFormFactors.SetModel(fFormFactorsModel); // <-- attach algorithm

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

double PaisQELLambdaPXSec::MHyperon ( const Interaction *  interaction ) const

private

Definition at line 136 of file PaisQELLambdaPXSec.cxx.

{
  const XclsTag & xcls = interaction->ExclTag();

  int pdgc  = xcls.StrangeHadronPdg();
  double MR = PDGLibrary::Instance()->Find(pdgc)->Mass();
  return MR;
}

bool PaisQELLambdaPXSec::ValidKinematics ( const Interaction *  i ) const

virtual

Is the input kinematical point a physically allowed one?

Reimplemented from genie::XSecAlgorithmI.

Definition at line 186 of file PaisQELLambdaPXSec.cxx.

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

  const InitialState & init_state  = interaction->InitState();
  double E = init_state.ProbeE(kRfHitNucRest);

  //resonance, final state primary lepton & nucleon mass
  double MR    = this -> MHyperon  (interaction);
  double ml    = interaction->FSPrimLepton()->Mass();
  double Mnuc  = init_state.Tgt().HitNucP4Ptr()->M();
  double Mnuc2 = TMath::Power(Mnuc,2);

  //resonance threshold
  double ER = ( TMath::Power(MR+ml,2) - Mnuc2 ) / (2*Mnuc);

  if(E <= ER) return false;

  return true;
}

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

virtual

Can this cross section algorithm handle the input process?

Implements genie::XSecAlgorithmI.

Definition at line 152 of file PaisQELLambdaPXSec.cxx.

{
  // Make sure we are dealing with one of the following channels:
  // v + n --> mu+ + Sigma^{-}
  // v + p --> mu+ + Lambda^{0}
  // v + p --> mu+ + Sigma^{0}

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

  const XclsTag &      xcls       = interaction->ExclTag();
  const InitialState & init_state = interaction->InitState();
  const ProcessInfo &  proc_info  = interaction->ProcInfo();

  bool is_exclusive_strange = (xcls.IsStrangeEvent() && !xcls.IsInclusiveStrange());
  if(!is_exclusive_strange) return false;

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

  bool isP = pdg::IsProton ( init_state.Tgt().HitNucPdg() );
  bool isN = pdg::IsNeutron( init_state.Tgt().HitNucPdg() );

  int pdgc = xcls.StrangeHadronPdg();

  bool can_handle = (
     (pdgc == kPdgSigmaM && isN) ||   /* v + n -> l + #Sigma^{-} */
     (pdgc == kPdgLambda && isP) ||  /* v + p -> l + #Lambda^{0} */
     (pdgc == kPdgSigma0  && isP)   /* v + p -> l + #Sigma^{0}  */
  );

  return can_handle;
}

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

virtual

Compute the cross section for the input interaction.

Implements genie::XSecAlgorithmI.

Definition at line 54 of file PaisQELLambdaPXSec.cxx.

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

  //----- get kinematics & init state - compute auxiliary vars
  const Kinematics &   kinematics  = interaction->Kine();
  const InitialState & init_state  = interaction->InitState();
  const Target &       target      = init_state.Tgt();

  //neutrino energy & momentum transfer
  double E   = init_state.ProbeE(kRfHitNucRest);
  double E2  = E * E;
  double q2  = kinematics.q2();


  //resonance mass & nucleon mass
  double Mnuc  = target.HitNucMass();
  double Mnuc2 = TMath::Power(Mnuc,2);

  //----- Calculate the differential cross section dxsec/dQ^2
  double Gf        = kGF2 / (2*kPi);
  double ml        = interaction->FSPrimLepton()->Mass();
  double ml2       = TMath::Power(ml,2);
  double M1        = Mnuc;
  double M2        = (this)->MHyperon(interaction);
  double v         = (TMath::Power(M2,2) - Mnuc2 - q2) / (2*Mnuc);
  double v2        = TMath::Power(v,2);
  double s         = Mnuc2 + 2*Mnuc*E;
  double u         = Mnuc2 + ml2 + 2*v*Mnuc - 2*Mnuc*E;

// xsec term changes sign for antineutrinos
  bool is_neutrino = pdg::IsNeutrino(init_state.ProbePdg());
  int sign = (is_neutrino) ? -1 : 1;

// Calculate the QEL form factors
  fFormFactors.Calculate(interaction);

  double F1V   = fFormFactors.F1V();
  double xiF2V = fFormFactors.xiF2V();
  double FA    = fFormFactors.FA();
//  double Fp    = fFormFactors.Fp();

// calculate w coefficients
   //start with Mass terms
  double Mp    = M2 + M1;
  double Mm    = M2 - M1;
  double Mm2   = TMath::Power(Mm, 2);
  double Mp2   = TMath::Power(Mp, 2);

   //Powers of Form Factors
  double FA2   = TMath::Power(FA, 2);
//  double FA3   = 0;

   //Calculate W terms

  double w1 = (Mm2 - q2)/(4*Mnuc2)*TMath::Power((F1V + xiF2V), 2) + (Mp2 - q2)/(4*Mnuc2) * FA2;
  double w2 = FA2 + TMath::Power((F1V + xiF2V - Mp * xiF2V / (2 * Mnuc)), 2) - q2 / Mnuc2 * TMath::Power((xiF2V / 2), 2);
  double w3 = 2 * FA * (F1V + xiF2V);

  double xsec = Gf*fSin8c2 / (16*Mnuc2*E2) * (-8*Mnuc2*q2*w1 - 4*(Mnuc2*v2 - q2)*w2 - sign*2*(s - u)*q2*w3 + (s-u)*(s-u)*w2);
  xsec = TMath::Max(xsec,0.);

  //----- The algorithm computes dxsec/dQ2
  //      Check whether variable tranformation is needed
  if(kps!=kPSQ2fE) {
    double J = utils::kinematics::Jacobian(interaction,kPSQ2fE,kps);
    xsec *= J;
  }

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

  //----- Nuclear cross section (simple scaling here)
  int nuc   = target.HitNucPdg();
  int NNucl = (pdg::IsProton(nuc)) ? target.Z() : target.N();
  xsec *= NNucl;

  return xsec;
}

Member Data Documentation

QELFormFactors genie::PaisQELLambdaPXSec::fFormFactors

mutableprivate

Definition at line 61 of file PaisQELLambdaPXSec.h.

const QELFormFactorsModelI* genie::PaisQELLambdaPXSec::fFormFactorsModel

private

Definition at line 62 of file PaisQELLambdaPXSec.h.

double genie::PaisQELLambdaPXSec::fSin8c2

private

Definition at line 64 of file PaisQELLambdaPXSec.h.

const XSecIntegratorI* genie::PaisQELLambdaPXSec::fXSecIntegrator

private

Definition at line 63 of file PaisQELLambdaPXSec.h.

---

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

• Generator/src/Physics/Strange/XSection/PaisQELLambdaPXSec.h
• Generator/src/Physics/Strange/XSection/PaisQELLambdaPXSec.cxx