An implementation of the neutrino - (free) nucleon [inverse beta decay] cross section, valid from the threshold energy (1.806MeV) up to hundreds of MeV. Currently cut off at 1/2 nucleon mass. Based on the Strumia/Vissani paper Phys.Lett.B564:42-54,2003. More...

#include <StrumiaVissaniIBDPXSec.h>

Inheritance diagram for genie::StrumiaVissaniIBDPXSec:

Public Member Functions
	StrumiaVissaniIBDPXSec ()

	StrumiaVissaniIBDPXSec (string config)

virtual	~StrumiaVissaniIBDPXSec ()

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 config)

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	dSigDt (const double sMinusU, const double sMinusMnuc, const double t) const

double	MtxElm (const double sMinusU, const double t) const

double	RadiativeCorr (const double Ee) const

double	FinalStateCorr (const double Ee) const

Static Private Member Functions
static double	MAterm (const double t, const double t2, const double f124, const double f22, const double g124, const double g224meM2, const double f1cf2R8, const double g1cg2R16me, const double g1cFsumR)

static double	MBterm (const double t, const double f1cf2, const double g1cg2, const double g1cFsumR, const double f22)

static double	MCterm (const double t, const double f124, const double f22, const double g124)

Private Attributes
double	fCosCabibbo2

double	fg1of0

double	fMa2

double	fMv2

double	fNucleonMMDiff

double	fEpsilon

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

An implementation of the neutrino - (free) nucleon [inverse beta decay] cross section, valid from the threshold energy (1.806MeV) up to hundreds of MeV. Currently cut off at 1/2 nucleon mass. Based on the Strumia/Vissani paper Phys.Lett.B564:42-54,2003.

Strumia A., Vissani F., Phys. Lett. B564, pp42-54 (2003)

Author: Corey Reed <cjreed nikhef.nl> Nikhef

June 22, 2009

Definition at line 32 of file StrumiaVissaniIBDPXSec.h.

Constructor & Destructor Documentation

genie::StrumiaVissaniIBDPXSec::StrumiaVissaniIBDPXSec ( )

StrumiaVissaniIBDPXSec::StrumiaVissaniIBDPXSec ( string config )

Definition at line 34 of file StrumiaVissaniIBDPXSec.cxx.

                                                             :
    XSecAlgorithmI("genie::StrumiaVissaniIBDPXSec", config),
    fXSecIntegrator(0)
 {
 
 }

StrumiaVissaniIBDPXSec::~StrumiaVissaniIBDPXSec ( )

virtual

Definition at line 41 of file StrumiaVissaniIBDPXSec.cxx.

 {
 
 }

Member Function Documentation

void StrumiaVissaniIBDPXSec::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 158 of file StrumiaVissaniIBDPXSec.cxx.

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

void StrumiaVissaniIBDPXSec::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 164 of file StrumiaVissaniIBDPXSec.cxx.

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

double StrumiaVissaniIBDPXSec::dSigDt	(	const double	sMinusU,
		const double	sMinusMnuc,
		const double	t
	)		const

private

Definition at line 214 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // return the differential cross section dS/dt. eqn 3 from reference
    // t = q^2
    //
    // for anue + p -> e+ + n , sMinusU = s - u  and  sMinusMnuc = s - m_p^2
    // for nue  + n -> e- + p , sMinusU = u - s  and  sMinusMnuc = s - m_n^2
    // where s = (p_nu + p_p)^2 and u = (p_nu - p_n)^2
 
    const double numer = kGF2 * fCosCabibbo2;
    const double denom = (2.000 * kPi) * sMinusMnuc*sMinusMnuc;
    assert(TMath::Abs(denom) > fEpsilon);  // avoid divide by zero
 
    return ( (numer / denom) * MtxElm(sMinusU, t) );
 }

double StrumiaVissaniIBDPXSec::FinalStateCorr ( const double Ee ) const

private

Definition at line 379 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // Sommerfeld factor; correction for final state interactions.
    // eqn 15 of the reference
 
    assert(Ee > fEpsilon); // must be non-zero and positive
    const double eta  = 2.000*kPi*kAem
                        / TMath::Sqrt(1.000 - (kElectronMass2 / (Ee*Ee)));
    const double expn = TMath::Exp(-1.000 * eta);
    assert(expn < 1.000);
    return ( eta / (1.000 - expn) );
 }

double StrumiaVissaniIBDPXSec::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 110 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // Compute the total cross section for a free nucleon target
 
    assert(interaction!=0);
    if(! this -> ValidProcess    (interaction) ) return 0.;
    if(! this -> ValidKinematics (interaction) ) return 0.;
 
    assert(fXSecIntegrator!=0);
    double xsec = fXSecIntegrator->Integrate(this, interaction);
 
    return xsec;
 }

void StrumiaVissaniIBDPXSec::LoadConfig ( void )

private

Definition at line 170 of file StrumiaVissaniIBDPXSec.cxx.

 {
 
    // cabibbo angle
    double cab ;
    GetParam( "CabibboAngle", cab ) ;
    const double cosCab = TMath::Cos(cab);
    fCosCabibbo2 = cosCab*cosCab;
 
    // form factor params
    GetParam( "QEL-FA0", fg1of0 ) ;
    double ma, mv ;
    GetParam( "QEL-Ma", ma ) ;
    GetParam( "QEL-Mv", mv ) ;
    fMa2 = ma*ma;
    fMv2 = mv*mv;
 
    // magnetic moments
 
    double mup, mun ;
    GetParam( "AnomMagnMoment-P", mup );
    GetParam( "AnomMagnMoment-N", mun );
    fNucleonMMDiff    = (mup - 1.000) - mun; // *anamolous* mag. mom. diff.
 
    // numeric
    int epmag ;
    GetParam("EpsilonMag", epmag ) ;
    fEpsilon = TMath::Power(10.000, -1.000 * static_cast<double>(epmag) );
 
    LOG("StrumiaVissani", pINFO) << "*** USING: cos2(Cabibbo)="
                                 << fCosCabibbo2
                                 << ", g1(0)=" << fg1of0
                                 << ", Ma^2=" << fMa2
                                 << ", Mv^2=" << fMv2
                                 << ", xi=" << fNucleonMMDiff
                                 << ", epsilon=" << fEpsilon;
 
    // load XSec Integrator
    fXSecIntegrator =
       dynamic_cast<const XSecIntegratorI *> (this->SubAlg("XSec-Integrator"));
    assert(fXSecIntegrator!=0);
 
 }

double StrumiaVissaniIBDPXSec::MAterm	(	const double	t,
		const double	t2,
		const double	f124,
		const double	f22,
		const double	g124,
		const double	g224meM2,
		const double	f1cf2R8,
		const double	g1cg2R16me,
		const double	g1cFsumR
	)

staticprivate

Definition at line 299 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // return A(t) in the matrix element calculation
    // from eqn 6 (without the factor 16)
    //
    // for speed purposes, no check that |t|^2 = t2 is performed
 
    // store multiply used terms
    const double tmme2 = t - kElectronMass2;
    const double tpme2 = t + kElectronMass2;
 
    double r1  = f124 * ( k4NucMass2 + tpme2);
           r1 += g124 * (-k4NucMass2 + tpme2);
           r1 += f22  * ( (t2/kNucleonMass2) + 4.000*tpme2 );
           r1 += g224meM2 * t;
           r1 += f1cf2R8 * (2.000*t + kElectronMass2);
           r1 += g1cg2R16me;
           r1 *= tmme2;
 
    double r2  = (f124 + (t * (f22 / kNucleonMass2))) * (k4NucMass2 + tmme2);
           r2 +=  g124                                * (k4NucMass2 - tmme2);
           r2 += g224meM2 * tmme2;
           r2 += f1cf2R8 * (2.000*t - kElectronMass2);
           r2 += g1cg2R16me;
           r2 *= kNucMassDiff2;
 
    const double r3 = 32.000 * kElectronMass2 * kNucleonMass * kNucMassDiff
                         * g1cFsumR;
 
    return ( r1 - r2 - r3 );
 }

double StrumiaVissaniIBDPXSec::MBterm	(	const double	t,
		const double	f1cf2,
		const double	g1cg2,
		const double	g1cFsumR,
		const double	f22
	)

staticprivate

Definition at line 339 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // return C(t) in the matrix element calculation
    // from eqn 6 (without the factor 16)
 
    double bterm  = 16.000 * t * g1cFsumR;
           bterm += ( k4EleMass2 * kNucMassDiff
                      * (f22 + (f1cf2 + 2.000*g1cg2)) ) / kNucleonMass2;
    return bterm;
 }

double StrumiaVissaniIBDPXSec::MCterm	(	const double	t,
		const double	f124,
		const double	f22,
		const double	g124
	)

staticprivate

Definition at line 354 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // return C(t) in the matrix element calculation
    // from eqn 6 (without the factor 16)
 
    return ( f124 + g124 - (t * ( f22 / kNucleonMass2 )) );
 }

double StrumiaVissaniIBDPXSec::MtxElm	(	const double	sMinusU,
		const double	t
	)		const

private

Definition at line 232 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // return the square of the matrix element. eqn 5 from the reference paper
    // |M^2| = A(t) - (s-u)B(t) + (s-u)^2 C(t)
    //
    // factor 16 comes from eqn 6
    //
    // for anue + p -> e+ + n , sMinusU = s - u
    // for nue  + n -> e- + p , sMinusU = u - s
    // where s = (p_nu + p_p)^2 and u = (p_nu - p_n)^2
 
    // store multiply used variables to reduce number of calculations
    const double t4m      = t / k4NucMass2;
    const double t2       = t * t;
 
    const double fdenomB  = 1.000 - (t / fMv2);
    const double fdenom   = (1.000 - t4m)*fdenomB*fdenomB;
    const double g1denom  = 1.000 - (t / fMa2);
    const double g2denom  = kPionMass2 - t;
    assert(TMath::Abs(fdenom)  > fEpsilon);   // avoid divide by zero
    assert(TMath::Abs(g1denom) > fEpsilon);   // avoid divide by zero
    assert(TMath::Abs(g2denom) > fEpsilon);   // avoid divide by zero
 
    const double f1       = (1.000 - ( (1.000+fNucleonMMDiff) * t4m)) / fdenom;
    const double f2       = fNucleonMMDiff / fdenom;
    const double g1       = fg1of0 / (g1denom*g1denom);
    const double g2       = (2.000 * kNucleonMass2 * g1) / g2denom;
 
    const double f12      = f1 * f1;
    const double f124     = 4.000 * f12;
    const double f22      = f2 * f2;
    const double g12      = g1 * g1;
    const double g124     = 4.000 * g12;
    const double g22      = g2 * g2;
    const double g224meM2 = 4.000 * g22 * kElectronMass2 / kNucleonMass2;
 
    const double g1cFsumR   = g1 * (f1+f2);
    const double f1cf2      = f1 * f2;
    const double g1cg2      = g1 * g2;
    const double f1cf2R8    = f1cf2 * 8.000;
    const double g1cg2R16me = g1cg2 * 16.000 * kElectronMass2;
 
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
    LOG("StrumiaVissani", pDEBUG) << "*** t = " << t
                                  << ", g2 = " << g2
                                  << ", g1 = " << g1
                                  << ", f1 = " << f1
                                  << ", f2 = " << f2;
 #endif
 
    // ok - now calculate the terms of the matrix element
    const double mat = MAterm(t, t2, f124, f22, g124,
                              g224meM2, f1cf2R8, g1cg2R16me, g1cFsumR);
    const double mbt = MBterm(t, f1cf2, g1cg2, g1cFsumR, f22);
    const double mct = MCterm(t, f124, f22, g124);
 
    const double M2  = mat - (sMinusU * (mbt - (sMinusU * mct)));
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
    LOG("StrumiaVissani", pDEBUG) << "*** Matrix element = " << (M2 / 16.000)
                                  << " [16A=" << mat << "] [16B=" << mbt
                                  << "] [16C=" << mct << "]";
 #endif
 
    return ( M2 / 16.000 );
 }

double StrumiaVissaniIBDPXSec::RadiativeCorr ( const double Ee ) const

private

Definition at line 365 of file StrumiaVissaniIBDPXSec.cxx.

 {
    // radiative correction to the cross section. eqn 14 from the reference
    // only valid for Ev<<m_p!
 
    assert(Ee > fEpsilon); // must be non-zero and positive
    double rc  = 6.000 + (1.500 * TMath::Log(kProtonMass / (2.000*Ee)));
           rc += 1.200 * TMath::Power((kElectronMass / Ee), 1.500);
           rc *= kAem / kPi;
           rc += 1.000;
    return rc;
 
 }

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

virtual

Is the input kinematical point a physically allowed one?

Reimplemented from genie::XSecAlgorithmI.

Definition at line 140 of file StrumiaVissaniIBDPXSec.cxx.

 {
    if(interaction->TestBit(kISkipKinematicChk)) return true;
 
    const InitialState & init_state = interaction -> InitState();
    const double Ev = init_state.ProbeE(kRfHitNucRest);
    static const double Ecutoff = kNucleonMass / 2;
    if (Ev > Ecutoff) {
       LOG("StrumiaVissani", pERROR) << "*** Ev=" << Ev
                                     << " is too large for VLE QEL!";
    } else if (init_state.IsNuBarP() || init_state.IsNuN()) {
       const KPhaseSpace & kps = interaction->PhaseSpace();
       return kps.IsAboveThreshold();
    }
 
    return false;
 }

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

virtual

Can this cross section algorithm handle the input process?

Implements genie::XSecAlgorithmI.

Definition at line 124 of file StrumiaVissaniIBDPXSec.cxx.

 {
   if(interaction->TestBit(kISkipProcessChk)) return true;
 
   // should be IBD and either nu_e + n or anu_e + p
   if (interaction->ProcInfo().IsInverseBetaDecay()) {
 
      const InitialState & init_state = interaction -> InitState();
      const Target & target = init_state.Tgt();
      if ( (target.IsProton() && pdg::IsAntiNuE(init_state.ProbePdg())) || (target.IsNeutron() && pdg::IsNuE(init_state.ProbePdg()) ))
                 return true;
   }
   LOG("StrumiaVissani", pERROR) << "*** Should be IBD processes either nu_e + n or anu_e + p!";
   return false;
 }

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

virtual

Compute the cross section for the input interaction.

Implements genie::XSecAlgorithmI.

Definition at line 46 of file StrumiaVissaniIBDPXSec.cxx.

 {
   // compute the differential cross section ds/dt
 
   if(! this -> ValidProcess    (interaction) ) return 0.;
   if(! this -> ValidKinematics (interaction) ) return 0.;
 
   const InitialState & init_state = interaction -> InitState();
   const double         Ev     = init_state.ProbeE(kRfHitNucRest);
   const Target &       target = init_state.Tgt();
   const bool           isProt = target.IsProton();
   const Kinematics &   kine   = interaction->Kine();
   const double         q2     = kine.q2();
   const double         mp     = (isProt) ? kProtonMass   : kNeutronMass;
   const double         mp2    = (isProt) ? kProtonMass2  : kNeutronMass2;
   const double         mn2    = (isProt) ? kNeutronMass2 : kProtonMass2;
 
   // calculate s-u and s-m_nucleon^2 in nucleon rest frame
   // need E_e
   const double Ee  = Ev + ( (q2 - mn2 + mp2) / (2.000*mp) );
   const double sMinusU   = ((2.000*mp*(Ev+Ee)) - kElectronMass2)
                            * (isProt ? 1.000 : -1.000);
   const double sMinusMp2 = 2.000*mp*Ev;
 
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
   LOG("StrumiaVissani", pDEBUG) << "*** Ev = " << Ev
                                 << ", q2 = " << q2
                                 << ", Ee = " << Ee
                                 << ", s-u = " << sMinusU
                                 << ", s-Mp2 = " << sMinusMp2;
 #endif
 
         double xsec = dSigDt(sMinusU, sMinusMp2, q2);
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
   LOG("StrumiaVissani", pDEBUG) << "*** dSdt = " << xsec;
 #endif
 
   // apply correction factors
   const double rdcf = RadiativeCorr(Ee);
   const double fscf = (isProt) ? 1.00 : FinalStateCorr(Ee);
   xsec *= rdcf * fscf;
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
   LOG("StrumiaVissani", pDEBUG) << "*** rad.corr. = " << rdcf
                                 << ", fin.st.cor. = " << fscf
                                 << ", xsec = " << xsec;
 #endif
 
   //----- The algorithm computes dxsec/dt, t=q^2
   //      Check whether variable tranformation is needed
   if(kps!=kPSq2fE && kps!=kPSQ2fE) {
      const double J = utils::kinematics::Jacobian(interaction,kPSq2fE,kps);
      xsec *= J;
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
      LOG("StrumiaVissani", pDEBUG) << "*** Jacobian = " << J;
 #endif
   }
 
 #ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
   LOG("StrumiaVissani", pDEBUG) << "*** xsec = " << xsec;
 #endif
   return xsec;
 }

Member Data Documentation

double genie::StrumiaVissaniIBDPXSec::fCosCabibbo2

private

Definition at line 81 of file StrumiaVissaniIBDPXSec.h.

double genie::StrumiaVissaniIBDPXSec::fEpsilon

private

Definition at line 86 of file StrumiaVissaniIBDPXSec.h.

double genie::StrumiaVissaniIBDPXSec::fg1of0

private

Definition at line 82 of file StrumiaVissaniIBDPXSec.h.

double genie::StrumiaVissaniIBDPXSec::fMa2

private

Definition at line 83 of file StrumiaVissaniIBDPXSec.h.

double genie::StrumiaVissaniIBDPXSec::fMv2

private

Definition at line 84 of file StrumiaVissaniIBDPXSec.h.

double genie::StrumiaVissaniIBDPXSec::fNucleonMMDiff

private

Definition at line 85 of file StrumiaVissaniIBDPXSec.h.

const XSecIntegratorI* genie::StrumiaVissaniIBDPXSec::fXSecIntegrator

private

Definition at line 88 of file StrumiaVissaniIBDPXSec.h.

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

Generator/src/Physics/InverseBetaDecay/XSection/StrumiaVissaniIBDPXSec.h
Generator/src/Physics/InverseBetaDecay/XSection/StrumiaVissaniIBDPXSec.cxx

Public Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation