EvtVectorIsr Class Reference

#include <EvtVectorIsr.hh>

Inheritance diagram for EvtVectorIsr:

Public Member Functions
	EvtVectorIsr ()
virtual	~EvtVectorIsr ()
void	getName (std::string &name)
EvtDecayBase *	clone ()
void	decay (EvtParticle *p)
void	init ()
void	initProbMax ()
Public Member Functions inherited from EvtDecayIncoherent
void	makeDecay (EvtParticle *p)
virtual	~EvtDecayIncoherent ()
void	setDaughterSpinDensity (int daughter)
int	isDaughterSpinDensitySet (int daughter)
Public Member Functions inherited from EvtDecayBase
virtual std::string	commandName ()
virtual void	command (std::string cmd)
double	getProbMax (double prob)
double	resetProbMax (double prob)
	EvtDecayBase ()
virtual	~EvtDecayBase ()
virtual bool	matchingDecay (const EvtDecayBase &other) const
EvtId	getParentId ()
double	getBranchingFraction ()
void	disableCheckQ ()
void	checkQ ()
int	getNDaug ()
EvtId *	getDaugs ()
EvtId	getDaug (int i)
int	getNArg ()
int	getPHOTOS ()
void	setPHOTOS ()
void	setVerbose ()
void	setSummary ()
double *	getArgs ()
std::string *	getArgsStr ()
double	getArg (int j)
std::string	getArgStr (int j)
std::string	getModelName ()
int	getDSum ()
int	summary ()
int	verbose ()
void	saveDecayInfo (EvtId ipar, int ndaug, EvtId *daug, int narg, std::vector< std::string > &args, std::string name, double brfr)
void	printSummary ()
void	setProbMax (double prbmx)
void	noProbMax ()
void	checkNArg (int a1, int a2=-1, int a3=-1, int a4=-1)
void	checkNDaug (int d1, int d2=-1)
void	checkSpinParent (EvtSpinType::spintype sp)
void	checkSpinDaughter (int d1, EvtSpinType::spintype sp)
virtual int	nRealDaughters ()

Additional Inherited Members
Static Public Member Functions inherited from EvtDecayBase
static void	findMasses (EvtParticle *p, int ndaugs, EvtId daugs[10], double masses[10])
static void	findMass (EvtParticle *p)
static double	findMaxMass (EvtParticle *p)
Protected Member Functions inherited from EvtDecayBase
bool	daugsDecayedByParentModel ()
Protected Attributes inherited from EvtDecayBase
bool	_daugsDecayedByParentModel

Detailed Description

Definition at line 30 of file EvtVectorIsr.hh.

Constructor & Destructor Documentation

EvtVectorIsr()

EvtVectorIsr::EvtVectorIsr ( )

inline

Definition at line 33 of file EvtVectorIsr.hh.

{}

Referenced by clone().

~EvtVectorIsr()

EvtVectorIsr::~EvtVectorIsr ( )

virtual

Definition at line 34 of file EvtVectorIsr.cc.

{}

Member Function Documentation

clone()

EvtDecayBase * EvtVectorIsr::clone ( )

virtual

Implements EvtDecayBase.

Definition at line 38 of file EvtVectorIsr.cc.

{ return new EvtVectorIsr; }

decay()

void EvtVectorIsr::decay ( EvtParticle * p )

virtual

Implements EvtDecayBase.

Definition at line 58 of file EvtVectorIsr.cc.

                                         {
 
  EvtParticle* phi;
  EvtParticle* gamma;
 
  // the elctron mass
  double electMass = EvtPDL::getMeanMass( EvtPDL::getId( "e-" ) );
 
  // get pointers to the daughters set
  // get masses/initial phase space - will overwrite the
  // p4s below to get the kinematic distributions correct
  p->initializePhaseSpace( getNDaug(), getDaugs() );
  phi   = p->getDaug( 0 );
  gamma = p->getDaug( 1 );
 
  double wcm  = p->mass();
  double beta = 2. * electMass / wcm;     // electMass/Ebeam = betagamma
  beta        = sqrt( 1. - beta * beta ); // sqrt (1 - (m/ebeam)**2)
 
  // gamma momentum in the parents restframe
  double pg = ( wcm * wcm - phi->mass() * phi->mass() ) / ( 2 * wcm );
 
  //    //generate kinematics according to Bonneau-Martin article
  //    //Nucl. Phys. B27 (1971) 381-397
 
  //    double y=pow((1+csmn)/(1-csmn),EvtRandom::Flat(0.0,1.0));
  //    double cs=kcs*(y-1)/(y+1);
 
  // For backward compatibility with .dec files before SP5, the backward cos limit for
  // the ISR photon is actually given as *minus* the actual limit. Sorry, this wouldn't be
  // my choice.  -Joe
 
  double ymax = log( ( 1. + beta * csfrmn ) / ( 1. - beta * csfrmn ) );
  double ymin = log( ( 1. - beta * csbkmn ) / ( 1. + beta * csbkmn ) );
 
  // photon theta distributed as  2*beta/(1-beta**2*cos(theta)**2)
  double y  = ( ymax - ymin ) * EvtRandom::Flat( 0.0, 1.0 ) + ymin;
  double cs = exp( y );
  cs        = ( cs - 1. ) / ( cs + 1. ) / beta;
  double sn = sqrt( 1 - cs * cs );
 
  double fi = EvtRandom::Flat( EvtConst::twoPi );
 
  // four-vector for the phi
  EvtVector4R p4phi( sqrt( phi->mass() * phi->mass() + pg * pg ), pg * sn * cos( fi ),
                     pg * sn * sin( fi ), pg * cs );
 
  EvtVector4R p4gamma( pg, -p4phi.get( 1 ), -p4phi.get( 2 ), -p4phi.get( 3 ) );
 
  // save momenta for particles
  phi->init( getDaug( 0 ), p4phi );
  gamma->init( getDaug( 1 ), p4gamma );
 
  // try setting the spin density matrix of the phi
 
  // first get the polarization vectors of the gamma and phi
 
  EvtVector4C phi0 = phi->epsParent( 0 );
  EvtVector4C phi1 = phi->epsParent( 1 );
  EvtVector4C phi2 = phi->epsParent( 2 );
 
  EvtVector4C gamma0 = gamma->epsParentPhoton( 0 );
  EvtVector4C gamma1 = gamma->epsParentPhoton( 1 );
 
  EvtComplex r1p = phi0 * gamma0;
  EvtComplex r2p = phi1 * gamma0;
  EvtComplex r3p = phi2 * gamma0;
 
  EvtComplex r1m = phi0 * gamma1;
  EvtComplex r2m = phi1 * gamma1;
  EvtComplex r3m = phi2 * gamma1;
 
  EvtComplex rho33 = r3p * conj( r3p ) + r3m * conj( r3m );
  EvtComplex rho22 = r2p * conj( r2p ) + r2m * conj( r2m );
  EvtComplex rho11 = r1p * conj( r1p ) + r1m * conj( r1m );
 
  EvtComplex rho13 = r3p * conj( r1p ) + r3m * conj( r1m );
  EvtComplex rho12 = r2p * conj( r1p ) + r2m * conj( r1m );
  EvtComplex rho23 = r3p * conj( r2p ) + r3m * conj( r2m );
 
  EvtComplex rho31 = conj( rho13 );
  EvtComplex rho32 = conj( rho23 );
  EvtComplex rho21 = conj( rho12 );
 
  EvtSpinDensity rho;
  rho.SetDim( 3 );
 
  rho.Set( 0, 0, rho11 );
  rho.Set( 0, 1, rho12 );
  rho.Set( 0, 2, rho13 );
  rho.Set( 1, 0, rho21 );
  rho.Set( 1, 1, rho22 );
  rho.Set( 1, 2, rho23 );
  rho.Set( 2, 0, rho31 );
  rho.Set( 2, 1, rho32 );
  rho.Set( 2, 2, rho33 );
 
  setDaughterSpinDensity( 0 );
  phi->setSpinDensityForward( rho );
 
  return;
}

getName()

void EvtVectorIsr::getName ( std::string & name )

virtual

Implements EvtDecayBase.

Definition at line 36 of file EvtVectorIsr.cc.

{ model_name = "VECTORISR"; }

init()

void EvtVectorIsr::init ( )

virtual

Reimplemented from EvtDecayBase.

Definition at line 40 of file EvtVectorIsr.cc.

                        {
 
  // check that there are 2 arguments
  checkNArg( 2 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::VECTOR );
  checkSpinDaughter( 0, EvtSpinType::VECTOR );
  checkSpinDaughter( 1, EvtSpinType::PHOTON );
 
  // copy the arguments into eaiser to remember names
 
  csfrmn = getArg( 0 );
  csbkmn = getArg( 1 );
}

initProbMax()

void EvtVectorIsr::initProbMax ( )

virtual

Reimplemented from EvtDecayBase.

Definition at line 56 of file EvtVectorIsr.cc.

{ noProbMax(); }

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

• EvtVectorIsr.hh
• EvtVectorIsr.cc