EvtPBB2.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 @IHEP
//
// Module: EvtPBB2.cc
//
// Description: Routine to decay pseudoscalar to  B_10 bar B_10 using
//              helicity amplitude.
//
// Modification history:
//
//     Ping R.-G.    Apr., 2007       Module created
//
//------------------------------------------------------------------------
 
#include "EvtPBB2.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtHelSys.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtRaritaSchwinger.hh"
#include "../EvtGenBase/EvtRaritaSchwingerParticle.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include "../EvtGenBase/EvtVector4R.hh"
#include "../EvtGenBase/EvtdFunctionSingle.hh"
#include <stdlib.h>
 
#include <string>
 
using std::cout;
using std::endl;
EvtPBB2::~EvtPBB2() {}
 
void EvtPBB2::getName( std::string& model_name ) { model_name = "PBB2"; }
 
EvtDecayBase* EvtPBB2::clone() { return new EvtPBB2; }
 
void EvtPBB2::init() {
  checkNDaug( 2 );
  checkSpinParent( EvtSpinType::SCALAR );
  checkSpinDaughter( 0, EvtSpinType::RARITASCHWINGER );
  checkSpinDaughter( 1, EvtSpinType::RARITASCHWINGER );
}
 
void EvtPBB2::initProbMax() {
 
  // Hard coded... should not be hard to calculate...
  double rt   = getArg( 0 );
  double pmax = 2 + 2 * rt * rt;
  setProbMax( pmax );
}
 
void EvtPBB2::decay( EvtParticle* p ) {
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  double rt  = getArg( 0 );
  double phs = getArg( 0 );
 
  int ii, jj;
  for ( ii = 0; ii < 4; ii++ )
  {
    for ( jj = 0; jj < 4; jj++ ) { vertex( ii, jj, 0 ); }
  }
 
  vertex( 0, 0, 1. );
  vertex( 1, 1, rt * exp( EvtComplex( 0, phs ) ) );
  vertex( 2, 2, -rt * exp( EvtComplex( 0, phs ) ) );
  vertex( 3, 3, -1 );
  return;
}