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:

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. 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 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? 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
double	fMa
	axial mass More...

double	fReIm
	Re/Im {forward pion scattering amplitude}. More...

double	fRo
	nuclear size scale parameter More...

bool	fModPCAC
	use modified PCAC (including f/s lepton mass) More...

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)

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

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.

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

March 11, 2005

Definition at line 40 of file ReinSehgalCOHPiPXSec.h.

Constructor & Destructor Documentation

ReinSehgalCOHPiPXSec::ReinSehgalCOHPiPXSec ( )

Definition at line 31 of file ReinSehgalCOHPiPXSec.cxx.

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

ReinSehgalCOHPiPXSec::ReinSehgalCOHPiPXSec ( string config )

Definition at line 37 of file ReinSehgalCOHPiPXSec.cxx.

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

ReinSehgalCOHPiPXSec::~ReinSehgalCOHPiPXSec ( )

virtual

Definition at line 43 of file ReinSehgalCOHPiPXSec.cxx.

 {
 
 }

Member Function Documentation

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();
 }

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();
 }

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;
 }

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);
 }

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;
 }

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;
 }

Member Data Documentation

double genie::ReinSehgalCOHPiPXSec::fMa

private

axial mass

Definition at line 61 of file ReinSehgalCOHPiPXSec.h.

bool genie::ReinSehgalCOHPiPXSec::fModPCAC

private

use modified PCAC (including f/s lepton mass)

Definition at line 64 of file ReinSehgalCOHPiPXSec.h.

double genie::ReinSehgalCOHPiPXSec::fReIm

private

Re/Im {forward pion scattering amplitude}.

Definition at line 62 of file ReinSehgalCOHPiPXSec.h.

double genie::ReinSehgalCOHPiPXSec::fRo

private

nuclear size scale parameter

Definition at line 63 of file ReinSehgalCOHPiPXSec.h.

const XSecIntegratorI* genie::ReinSehgalCOHPiPXSec::fXSecIntegrator

private

Definition at line 66 of file ReinSehgalCOHPiPXSec.h.

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

Generator/src/Physics/Coherent/XSection/ReinSehgalCOHPiPXSec.h
Generator/src/Physics/Coherent/XSection/ReinSehgalCOHPiPXSec.cxx

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation