genie::ReinSehgalCOHPiPXSec Class Reference

Computes the double differential cross section for CC & NC coherent pion production according to the Rein-Sehgal model. v(vbar)A->v(vbar)Api0, vA->l-Api+, vbarA->l+Api-. More...

#include <ReinSehgalCOHPiPXSec.h>

Inheritance diagram for genie::ReinSehgalCOHPiPXSec:

Collaboration diagram for genie::ReinSehgalCOHPiPXSec:

Public Member Functions
	ReinSehgalCOHPiPXSec ()
	ReinSehgalCOHPiPXSec (string config)
virtual	~ReinSehgalCOHPiPXSec ()
double	XSec (const Interaction *i, KinePhaseSpace_t k) const
	Compute the cross section for the input interaction.
double	Integral (const Interaction *i) const
bool	ValidProcess (const Interaction *i) const
	Can this cross section algorithm handle the input process?
void	Configure (const Registry &config)
void	Configure (string config)
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?
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.
virtual AlgStatus_t	GetStatus (void) const
	Get algorithm status.
virtual bool	AllowReconfig (void) const
virtual AlgCmp_t	Compare (const Algorithm *alg) const
	Compare with input algorithm.
virtual void	SetId (const AlgId &id)
	Set algorithm ID.
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.

Private Member Functions
void	LoadConfig (void)

Private Attributes
double	fMa
	axial mass
double	fReIm
	Re/Im {forward pion scattering amplitude}.
double	fRo
	nuclear size scale parameter
bool	fModPCAC
	use modified PCAC (including f/s lepton mass)
const XSecIntegratorI *	fXSecIntegrator

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)
static string	BuildParamMatKey (const std::string &comm_name, unsigned int i, unsigned int j)
static string	BuildParamMatRowSizeKey (const std::string &comm_name)
static string	BuildParamMatColSizeKey (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.
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.
int	GetParamVectKeys (const std::string &comm_name, std::vector< RgKey > &k, bool is_top_call=true) const
template<class T>
int	GetParamMat (const std::string &comm_name, TMatrixT< T > &mat, bool is_top_call=true) const
	Handle to load matrix of parameters.
template<class T>
int	GetParamMatSym (const std::string &comm_name, TMatrixTSym< T > &mat, bool is_top_call=true) const
int	GetParamMatKeys (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
int	AddLowRegistry (Registry *rp, bool owns=true)
	add registry with lowest priority, also update ownership
int	MergeTopRegistry (const Registry &r)
int	AddTopRegisties (const vector< Registry * > &rs, bool owns=false)
	Add registries with top priority, also udated Ownerships.
Protected Attributes inherited from genie::Algorithm
bool	fAllowReconfig
bool	fOwnsSubstruc
	true if it owns its substructure (sub-algs,...)
AlgId	fID
	algorithm name and configuration set
vector< Registry * >	fConfVect
vector< bool >	fOwnerships
	ownership for every registry in fConfVect
AlgStatus_t	fStatus
	algorithm execution status
AlgMap *	fOwnedSubAlgMp
	local pool for owned sub-algs (taken out of the factory pool)

Detailed Description

Computes the double differential cross section for CC & NC coherent pion production according to the Rein-Sehgal model. v(vbar)A->v(vbar)Api0, vA->l-Api+, vbarA->l+Api-.

The t-dependence of the triple differential cross (d^3xsec/dxdydt) is analytically integrated out.

Is a concrete implementation of the XSecAlgorithmI interface.

References:\n D.Rein and L.M.Sehgal, Coherent pi0 production in neutrino

reactions, Nucl.Phys.B223:29-144 (1983)

D.Rein and L.M.Sehgal, PCAC and the Deficit of Forward Muons in pi+ Production by Neutrinos, hep-ph/0606185

Author

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

Created:\n March 11, 2005

License:\n Copyright (c) 2003-2025, The GENIE Collaboration

For the full text of the license visit http://copyright.genie-mc.org

Definition at line 40 of file ReinSehgalCOHPiPXSec.h.

Constructor & Destructor Documentation

ReinSehgalCOHPiPXSec() [1/2]

ReinSehgalCOHPiPXSec::ReinSehgalCOHPiPXSec

(

)

Definition at line 31 of file ReinSehgalCOHPiPXSec.cxx.

                                           :
XSecAlgorithmI("genie::ReinSehgalCOHPiPXSec")
{
 
}

References genie::XSecAlgorithmI::XSecAlgorithmI().

ReinSehgalCOHPiPXSec() [2/2]

ReinSehgalCOHPiPXSec::ReinSehgalCOHPiPXSec

(

string

config

)

Definition at line 37 of file ReinSehgalCOHPiPXSec.cxx.

                                                        :
XSecAlgorithmI("genie::ReinSehgalCOHPiPXSec", config)
{
 
}

References genie::XSecAlgorithmI::XSecAlgorithmI().

~ReinSehgalCOHPiPXSec()

ReinSehgalCOHPiPXSec::~ReinSehgalCOHPiPXSec ( )

virtual

Definition at line 43 of file ReinSehgalCOHPiPXSec.cxx.

{
 
}

Member Function Documentation

Configure() [1/2]

void ReinSehgalCOHPiPXSec::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 176 of file ReinSehgalCOHPiPXSec.cxx.

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

References genie::Algorithm::Configure(), and LoadConfig().

Configure() [2/2]

void ReinSehgalCOHPiPXSec::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 182 of file ReinSehgalCOHPiPXSec.cxx.

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

References genie::Algorithm::Configure(), and LoadConfig().

Integral()

double ReinSehgalCOHPiPXSec::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 151 of file ReinSehgalCOHPiPXSec.cxx.

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

References fXSecIntegrator.

LoadConfig()

void ReinSehgalCOHPiPXSec::LoadConfig ( void )

private

Definition at line 188 of file ReinSehgalCOHPiPXSec.cxx.

{
 
  GetParam( "COH-Ma", fMa ) ;
  GetParam( "COH-Ro", fRo ) ;
  GetParam( "COH-ReImAmpl", fReIm ) ;
  GetParam( "COH-UseModifiedPCAC", fModPCAC ) ;
 
  //-- load the differential cross section integrator
  fXSecIntegrator =
      dynamic_cast<const XSecIntegratorI *> (this->SubAlg("XSec-Integrator"));
  assert(fXSecIntegrator);
}

References fMa, fModPCAC, fReIm, fRo, fXSecIntegrator, genie::Algorithm::GetParam(), and genie::Algorithm::SubAlg().

Referenced by Configure(), and Configure().

ValidProcess()

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

virtual

Can this cross section algorithm handle the input process?

Implements genie::XSecAlgorithmI.

Definition at line 157 of file ReinSehgalCOHPiPXSec.cxx.

{
  if(interaction->TestBit(kISkipProcessChk)) return true;
 
  const InitialState & init_state = interaction->InitState();
  const ProcessInfo &  proc_info  = interaction->ProcInfo();
  const Target &       target     = init_state.Tgt();
 
  int nu = init_state.ProbePdg();
 
  if (!proc_info.IsCoherentProduction())  return false;
  if (!proc_info.IsWeak())      return false;
  if (target.HitNucIsSet())     return false;
  if (!(target.A()>1))          return false;
  if (!pdg::IsNeutrino(nu) && !pdg::IsAntiNeutrino(nu)) return false;
 
  return true;
}

References genie::Target::A(), genie::Target::HitNucIsSet(), genie::Interaction::InitState(), genie::pdg::IsAntiNeutrino(), genie::ProcessInfo::IsCoherentProduction(), genie::pdg::IsNeutrino(), genie::ProcessInfo::IsWeak(), genie::kISkipProcessChk, genie::InitialState::ProbePdg(), genie::Interaction::ProcInfo(), and genie::InitialState::Tgt().

Referenced by XSec().

XSec()

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

virtual

Compute the cross section for the input interaction.

Implements genie::XSecAlgorithmI.

Definition at line 48 of file ReinSehgalCOHPiPXSec.cxx.

{
  if(! this -> ValidProcess    (interaction) ) return 0.;
  if(! this -> ValidKinematics (interaction) ) return 0.;
 
  const Kinematics &   kinematics = interaction -> Kine();
  const InitialState & init_state = interaction -> InitState();
 
  //----- Compute the coherent NC pi0 production d2xsec/dxdy
  //      see page 34 in Nucl.Phys.B223:29-144 (1983)
  double E      = init_state.ProbeE(kRfLab); // neutrino energy
  double x      = kinematics.x(); // bjorken x
  double y      = kinematics.y(); // inelasticity y
  double Q2     = 2.*x*y*kNucleonMass*E;  // momentum transfer Q2>0
  double A      = (double) init_state.Tgt().A(); // mass number
  double A2     = TMath::Power(A,2.);
  double A_3    = TMath::Power(A,1./3.);
  double Gf     = kGF2 * kNucleonMass / (32 * kPi3);
  double fp     = 0.93 * kPionMass; // pion decay constant
  double fp2    = TMath::Power(fp,2.);
  double Epi    = y*E; // pion energy
  double ma2    = TMath::Power(fMa,2);
  double propg  = TMath::Power(ma2/(ma2+Q2),2.); // propagator term
  double r2     = TMath::Power(fReIm,2.);
  double sTot   = utils::hadxs::TotalPionNucleonXSec(Epi); // tot. pi+N xsec
  double sTot2  = TMath::Power(sTot,2.);
  double sInel  = utils::hadxs::InelasticPionNucleonXSec(Epi); // inel. pi+N xsec
  double Ro2    = TMath::Power(fRo*units::fermi,2.);
 
  // effect of pion absorption in the nucleus
  double Fabs   = TMath::Exp( -9.*A_3*sInel / (16.*kPi*Ro2) );
 
  // the xsec in Nucl.Phys.B223:29-144 (1983) is d^3xsec/dxdydt but the only
  // t-dependent factor is an exp(-bt) so it can be integrated analyticaly
  double Epi2   = TMath::Power(Epi,2.);
  double R      = fRo * A_3 * units::fermi; // nuclear radius
  double R2     = TMath::Power(R,2.);
  double b      = 0.33333 * R2;
  double MxEpi  = kNucleonMass*x/Epi;
  double mEpi2  = kPionMass2/Epi2;
  double tA     = 1. + MxEpi - 0.5*mEpi2;
  double tB     = TMath::Sqrt(1. + 2*MxEpi) * TMath::Sqrt(1.-mEpi2);
  double tmin   = 2*Epi2 * (tA-tB);
  double tmax   = 2*Epi2 * (tA+tB);
  double tint   = (TMath::Exp(-b*tmin) - TMath::Exp(-b*tmax))/b; // t integral
 
  double xsec = Gf*fp2 * A2 * E*(1-y) * sTot2 * (1+r2)*propg * Fabs*tint;
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("ReinSehgalCohPi", pDEBUG)
      << "\n momentum transfer .............. Q2    = " << Q2
      << "\n mass number .................... A     = " << A
      << "\n pion energy .................... Epi   = " << Epi
      << "\n propagator term ................ propg = " << propg
      << "\n Re/Im of fwd pion scat. ampl. .. Re/Im = " << fReIm
      << "\n total pi+N cross section ....... sigT  = " << sTot
      << "\n inelastic pi+N cross section ... sigI  = " << sInel
      << "\n nuclear size scale ............. Ro    = " << fRo
      << "\n pion absorption factor ......... Fabs  = " << Fabs
      << "\n t integration range ............ [" << tmin << "," << tmax << "]"
      << "\n t integration factor ........... tint  = " << tint;
#endif
 
  // compute the cross section for the CC case
 
  if(interaction->ProcInfo().IsWeakCC()) {
     // Check whether a modification to Adler's PCAC theorem is applied for
     // including the effect of the muon mass.
     // See Rein and Sehgal, PCAC and the Deficit of Forward Muons in pi+
     // Production by Neutrinos, hep-ph/0606185
     double C = 1.;
     if(fModPCAC) {
        double ml    = interaction->FSPrimLepton()->Mass();
        double ml2   = TMath::Power(ml,2);
        double Q2min = ml2 * y/(1-y);
        if(Q2>Q2min) {
           double C1    = TMath::Power(1-0.5*Q2min/(Q2+kPionMass2), 2);
           double C2    = 0.25*y*Q2min*(Q2-Q2min)/ TMath::Power(Q2+kPionMass2,2);
           C = C1+C2;
        } else {
           C = 0.;
        }
     }
     xsec *= (2.*C);
  }
 
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("ReinSehgalCohPi", pINFO)
         << "d2xsec/dxdy[COHPi] (x= " << x << ", y="
                       << y << ", E=" << E << ") = "<< xsec;
#endif
 
  //----- The algorithm computes d^2xsec/dxdy
  //      Check whether variable tranformation is needed
  if(kps!=kPSxyfE) {
    double J = utils::kinematics::Jacobian(interaction,kPSxyfE,kps);
    xsec *= J;
  }
 
  return xsec;
}

References genie::Target::A(), genie::units::fermi, fMa, fModPCAC, fReIm, fRo, genie::Interaction::FSPrimLepton(), genie::utils::hadxs::InelasticPionNucleonXSec(), genie::ProcessInfo::IsWeakCC(), genie::utils::kinematics::Jacobian(), genie::constants::kGF2, genie::constants::kNucleonMass, genie::constants::kPi, genie::constants::kPi3, genie::constants::kPionMass, genie::constants::kPionMass2, genie::kPSxyfE, genie::kRfLab, LOG, pDEBUG, pINFO, genie::InitialState::ProbeE(), genie::Interaction::ProcInfo(), genie::InitialState::Tgt(), genie::utils::hadxs::TotalPionNucleonXSec(), genie::XSecAlgorithmI::ValidKinematics(), and ValidProcess().

Member Data Documentation

fMa

double genie::ReinSehgalCOHPiPXSec::fMa

private

axial mass

Definition at line 61 of file ReinSehgalCOHPiPXSec.h.

Referenced by LoadConfig(), and XSec().

fModPCAC

bool genie::ReinSehgalCOHPiPXSec::fModPCAC

private

use modified PCAC (including f/s lepton mass)

Definition at line 64 of file ReinSehgalCOHPiPXSec.h.

Referenced by LoadConfig(), and XSec().

fReIm

double genie::ReinSehgalCOHPiPXSec::fReIm

private

Re/Im {forward pion scattering amplitude}.

Definition at line 62 of file ReinSehgalCOHPiPXSec.h.

Referenced by LoadConfig(), and XSec().

fRo

double genie::ReinSehgalCOHPiPXSec::fRo

private

nuclear size scale parameter

Definition at line 63 of file ReinSehgalCOHPiPXSec.h.

Referenced by LoadConfig(), and XSec().

fXSecIntegrator

const XSecIntegratorI* genie::ReinSehgalCOHPiPXSec::fXSecIntegrator

private

Definition at line 66 of file ReinSehgalCOHPiPXSec.h.

Referenced by Integral(), and LoadConfig().

---

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

• ReinSehgalCOHPiPXSec.h
• ReinSehgalCOHPiPXSec.cxx