EvtSPL.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of models developed at BES collaboration
//      based on the EvtGen framework.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/BesCopyright
//      Copyright (A) 2006      Ping Rong-Gang, Pang Cai-Ying@IHEP
//
//
// Module: EvtSPL.cc
//
// Description: Routine to decay Sigma0->photon+Lambda by helicity amplitude.
//
// Modification history:
//
//    Ping R.-G.    Apr., 2006       Module created
//
//------------------------------------------------------------------------
//
#include "EvtSPL.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtHelSys.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include "../EvtGenBase/EvtVector4R.hh"
#include "../EvtGenBase/EvtdFunction.hh"
#include <stdlib.h>
#include <string>
using std::endl;
 
EvtSPL::~EvtSPL() {}
 
void EvtSPL::getName( std::string& model_name ) { model_name = "SPL"; }
 
EvtDecayBase* EvtSPL::clone() { return new EvtSPL; }
 
void EvtSPL::initProbMax() {
  double ProbMax = 4.;
  setProbMax( ProbMax );
}
 
void EvtSPL::init() {
  checkNDaug( 2 );
  checkSpinParent( EvtSpinType::DIRAC );
  checkSpinDaughter( 0, EvtSpinType::PHOTON );
  checkSpinDaughter( 1, EvtSpinType::DIRAC );
}
 
void EvtSPL::decay( EvtParticle* p ) {
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
  EvtParticle *v, *s1;
  EvtVector4R  pv, ps, ppr;
 
  v   = p->getDaug( 0 ); // photon
  s1  = p->getDaug( 1 ); // Lambda
  pv  = v->getP4Lab();
  ps  = s1->getP4Lab();
  ppr = p->getP4();
 
  //  Put phase space results into the daughters.
 
  EvtHelSys angles( ppr, pv ); // using helicity sys.angles
  double    theta = angles.getHelAng( 1 );
  double    phi   = angles.getHelAng( 2 );
  double    gamma = 0;
 
  vertex( 0, 0, 0, Djmn( 0.5, 0.5, 0.5, phi, theta, gamma ) );
  vertex( 0, 1, 1, -Djmn( 0.5, 0.5, -0.5, phi, theta, gamma ) );
  vertex( 1, 0, 0, Djmn( 0.5, -0.5, 0.5, phi, theta, gamma ) );
  vertex( 1, 1, 1, -Djmn( 0.5, -0.5, -0.5, phi, theta, gamma ) );
  vertex( 0, 0, 1, 0.0 );
  vertex( 0, 1, 0, 0.0 );
  vertex( 1, 0, 1, 0.0 );
  vertex( 1, 1, 0, 0.0 );
  return;
}