genie::QPMDISPXSec Class Reference

Computes DIS differential cross sections. Is a concrete implementation of the XSecAlgorithmI interface. More...

#include <QPMDISPXSec.h>

Inheritance diagram for genie::QPMDISPXSec:

Public Member Functions
	QPMDISPXSec ()
	QPMDISPXSec (string config)
virtual	~QPMDISPXSec ()
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
DISStructureFunc	fDISSF
bool	fInInitPhase
const DISStructureFuncModelI *	fDISSFModel
	SF model. More...
const XSecIntegratorI *	fXSecIntegrator
	diff. xsec integrator More...
const XSecAlgorithmI *	fCharmProdModel
double	fScale
	cross section scaling factor More...
double	fSin48w
	sin^4(Weingberg angle) More...

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 DIS differential cross sections. Is a concrete implementation of the XSecAlgorithmI interface.

E.A.Paschos and J.Y.Yu, Phys.Rev.D 65.03300

Author

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

May 05, 2004

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

Definition at line 33 of file QPMDISPXSec.h.

Constructor & Destructor Documentation

QPMDISPXSec::QPMDISPXSec

(

)

Definition at line 44 of file QPMDISPXSec.cxx.

                         :
XSecAlgorithmI("genie::QPMDISPXSec")
{
  fInInitPhase = true;
}

QPMDISPXSec::QPMDISPXSec

(

string

config

)

Definition at line 50 of file QPMDISPXSec.cxx.

                                      :
XSecAlgorithmI("genie::QPMDISPXSec", config)
{
  fInInitPhase = true;
}

QPMDISPXSec::~QPMDISPXSec ( )

virtual

Definition at line 56 of file QPMDISPXSec.cxx.

{

}

Member Function Documentation

void QPMDISPXSec::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 213 of file QPMDISPXSec.cxx.

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

void QPMDISPXSec::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 219 of file QPMDISPXSec.cxx.

{
  Algorithm::Configure(config);

  Registry r( "QPMDISPXSec_specific", false ) ;

  RgKey xdefkey = "XSecModel@genie::EventGenerator/DIS-CC-CHARM";
  RgKey local_key = "CharmXSec" ;
  r.Set( local_key, AlgConfigPool::Instance() -> GlobalParameterList() -> GetAlg(xdefkey) ) ;

  Algorithm::Configure(r) ;

  this->LoadConfig();
}

double QPMDISPXSec::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 188 of file QPMDISPXSec.cxx.

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

void QPMDISPXSec::LoadConfig ( void  )

private

Definition at line 234 of file QPMDISPXSec.cxx.

{
  // Access global defaults to use in case of missing parameters

  fDISSFModel = 0;
  fDISSFModel =
     dynamic_cast<const DISStructureFuncModelI *> (this->SubAlg("SFAlg"));
  assert(fDISSFModel);

  fDISSF.SetModel(fDISSFModel); // <-- attach algorithm

  // Cross section scaling factor
  GetParam( "DIS-XSecScale", fScale ) ;

  // sin^4(theta_weinberg)
  double thw  ;
  GetParam( "WeinbergAngle", thw ) ;
  fSin48w = TMath::Power( TMath::Sin(thw), 4 );


  // Since this method would be called every time the current algorithm is
  // reconfigured at run-time, remove all the data cached by this algorithm
  // since they depend on the previous configuration

  if(!fInInitPhase) {
     Cache * cache = Cache::Instance();
     string keysubstr = this->Id().Key() + "/DIS-RES-Join";
     cache->RmMatchedCacheBranches(keysubstr);
  }
  fInInitPhase = false;

  //-- load the differential cross section integrator
  fXSecIntegrator =
      dynamic_cast<const XSecIntegratorI *> (this->SubAlg("XSec-Integrator"));
  assert(fXSecIntegrator);

  // Load the charm production cross section model
  RgKey local_key = "CharmXSec" ;
  RgAlg xalg;
  GetParam( local_key, xalg ) ;
  LOG("DISXSec", pDEBUG)
     << "Loading the cross section model: " << xalg;

  fCharmProdModel = dynamic_cast<const XSecAlgorithmI *> ( this -> SubAlg(local_key) ) ;
  assert(fCharmProdModel);
}

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

virtual

Can this cross section algorithm handle the input process?

Implements genie::XSecAlgorithmI.

Definition at line 194 of file QPMDISPXSec.cxx.

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

  const ProcessInfo & proc_info  = interaction->ProcInfo();
  if(!proc_info.IsDeepInelastic()) return false;

  const InitialState & init_state = interaction -> InitState();
  int probe_pdg = init_state.ProbePdg();
  if(!pdg::IsLepton(probe_pdg)) return false;

  if(! init_state.Tgt().HitNucIsSet()) return false;

  int hitnuc_pdg = init_state.Tgt().HitNucPdg();
  if(!pdg::IsNeutronOrProton(hitnuc_pdg)) return false;

  return true;
}

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

virtual

Compute the cross section for the input interaction.

Implements genie::XSecAlgorithmI.

Definition at line 61 of file QPMDISPXSec.cxx.

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

  // Get kinematical & init-state parameters
  const Kinematics &   kinematics = interaction -> Kine();
  const InitialState & init_state = interaction -> InitState();
  const ProcessInfo &  proc_info  = interaction -> ProcInfo();

  double E     = init_state.ProbeE(kRfHitNucRest);
  double ml    = interaction->FSPrimLepton()->Mass();
  double Mnuc  = init_state.Tgt().HitNucMass();
  double x     = kinematics.x();
  double y     = kinematics.y();

  double E2    = E    * E;
  double ml2   = ml   * ml;
  double ml4   = ml2  * ml2;
  double Mnuc2 = Mnuc * Mnuc;

#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("DISPXSec", pDEBUG)
   << "Computing d2xsec/dxdy @ E = " << E << ", x = " << x << ", y = " << y;
#endif

  // One of the xsec terms changes sign for antineutrinos @ DIS/CC

  bool is_nubar_cc = pdg::IsAntiNeutrino(init_state.ProbePdg()) &&
                     proc_info.IsWeakCC();
  int sign = (is_nubar_cc) ? -1 : 1;

  // Calculate the DIS structure functions
  fDISSF.Calculate(interaction);

#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("DISPXSec", pDEBUG) << fDISSF;
#endif

  //
  // Compute the differential cross section
  //

  double g2 = kGF2;
  // For EM interaction replace  G_{Fermi} with :
  // a_{em} * pi / ( sqrt(2) * sin^2(theta_weinberg) * Mass_{W}^2 }
  // See C.Quigg, Gauge Theories of the Strong, Weak and E/M Interactions,
  // ISBN 0-8053-6021-2, p.112 (6.3.57)
  // Also, take int account that the photon propagator is 1/p^2 but the
  // W propagator is 1/(p^2-Mass_{W}^2), so weight the EM case with
  // Mass_{W}^4 / q^4
  // So, overall:
  // G_{Fermi}^2 --> a_{em}^2 * pi^2 / (2 * sin^4(theta_weinberg) * q^{4})
  //
  double Q2 = utils::kinematics::XYtoQ2(E,Mnuc,x,y);
  double Q4 = Q2*Q2;
  if(proc_info.IsEM()) {
    g2 = kAem2 * kPi2 / (2.0 * fSin48w * Q4);
  }
  if (proc_info.IsWeakCC()) {
    g2 = kGF2 * kMw2 * kMw2 / TMath::Power((Q2 + kMw2), 2);
  } else if (proc_info.IsWeakNC()) {
    g2 = kGF2 * kMz2 * kMz2 / TMath::Power((Q2 + kMz2), 2);
  }
  double front_factor = (g2*Mnuc*E) / kPi;

  // Build all dxsec/dxdy terms
  double term1 = y * ( x*y + ml2/(2*E*Mnuc) );
  double term2 = 1 - y - Mnuc*x*y/(2*E) - ml2/(4*E2);
  double term3 = sign * (x*y*(1-y/2) - y*ml2/(4*Mnuc*E));
  double term4 = x*y*ml2/(2*Mnuc*E) + ml4/(4*Mnuc2*E2);
  double term5 = -1.*ml2/(2*Mnuc*E);

#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("DISPXSec", pDEBUG)
    << "\nd2xsec/dxdy ~ (" << term1 << ")*F1+(" << term2 << ")*F2+("
                  << term3 << ")*F3+(" << term4 << ")*F4+(" << term5 << ")*F5";
#endif

  term1 *= fDISSF.F1();
  term2 *= fDISSF.F2();
  term3 *= fDISSF.F3();
  term4 *= fDISSF.F4();
  term5 *= fDISSF.F5();

  double xsec = front_factor * (term1 + term2 + term3 + term4 + term5);
  xsec = TMath::Max(xsec,0.);

#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("DISPXSec", pINFO)
        << "d2xsec/dxdy[FreeN] (E= " << E
                      << ", x= " << x << ", y= " << y << ") = " << 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;
  }

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

  // Compute nuclear cross section (simple scaling here, corrections must
  // have been included in the structure functions)
  const Target & target = init_state.Tgt();
  int nucpdgc = target.HitNucPdg();
  int NNucl = (pdg::IsProton(nucpdgc)) ? target.Z() : target.N();
  xsec *= NNucl;

  // Apply scaling / if required to reach well known asymmptotic value
  xsec *= fScale;

  // Subtract the inclusive charm production cross section
  interaction->ExclTagPtr()->SetCharm();
  double xsec_charm = fCharmProdModel->XSec(interaction,kps);
  interaction->ExclTagPtr()->UnsetCharm();
#ifdef __GENIE_LOW_LEVEL_MESG_ENABLED__
  LOG("DISPXSec", pINFO)
       << "Subtracting charm piece: " << xsec_charm << " / out of " << xsec;
#endif
  xsec = TMath::Max(0., xsec-xsec_charm);
  return xsec;
}

Member Data Documentation

const XSecAlgorithmI* genie::QPMDISPXSec::fCharmProdModel

private

Definition at line 59 of file QPMDISPXSec.h.

DISStructureFunc genie::QPMDISPXSec::fDISSF

mutableprivate

Definition at line 53 of file QPMDISPXSec.h.

const DISStructureFuncModelI* genie::QPMDISPXSec::fDISSFModel

private

SF model.

Definition at line 56 of file QPMDISPXSec.h.

bool genie::QPMDISPXSec::fInInitPhase

private

Definition at line 54 of file QPMDISPXSec.h.

double genie::QPMDISPXSec::fScale

private

cross section scaling factor

Definition at line 61 of file QPMDISPXSec.h.

double genie::QPMDISPXSec::fSin48w

private

sin^4(Weingberg angle)

Definition at line 62 of file QPMDISPXSec.h.

const XSecIntegratorI* genie::QPMDISPXSec::fXSecIntegrator

private

diff. xsec integrator

Definition at line 57 of file QPMDISPXSec.h.

---

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

• Generator/src/Physics/DeepInelastic/XSection/QPMDISPXSec.h
• Generator/src/Physics/DeepInelastic/XSection/QPMDISPXSec.cxx