EvtBtoKD3P.cc

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//-----------------------------------------------------------------------
// File and Version Information:
//      $Id: EvtBtoKD3P.cc,v 1.2 2009/12/18 08:43:52 pingrg Exp $
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations. If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information:
//      Copyright (C) 2003, Colorado State University
//
// Module creator:
//      Abi soffer, CSU, 2003
//-----------------------------------------------------------------------
#include "../EvtGenBase/EvtPatches.hh"
 
// Decay model that does the decay B+->D0K, D0->3 psudoscalars
 
#include <assert.h>
 
#include "../EvtGenBase/EvtDecayTable.hh"
#include "../EvtGenBase/EvtId.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtRandom.hh"
#include "EvtBtoKD3P.hh"
#include "EvtPto3P.hh"
 
#include "../EvtGenBase/EvtCyclic3.hh"
#include "../EvtGenBase/EvtDalitzPoint.hh"
using std::endl;
 
//------------------------------------------------------------------
EvtBtoKD3P::EvtBtoKD3P() : _model1( 0 ), _model2( 0 ), _decayedOnce( false ) {}
 
//------------------------------------------------------------------
EvtBtoKD3P::EvtBtoKD3P( const EvtBtoKD3P& other ) {}
 
//------------------------------------------------------------------
EvtBtoKD3P::~EvtBtoKD3P() {}
 
//------------------------------------------------------------------
EvtDecayBase* EvtBtoKD3P::clone() { return new EvtBtoKD3P(); }
 
//------------------------------------------------------------------
void EvtBtoKD3P::getName( std::string& model_name ) { model_name = "BTOKD3P"; }
 
//------------------------------------------------------------------
void EvtBtoKD3P::init() {
  checkNArg( 2 );  // r, phase
  checkNDaug( 3 ); // K, D0(allowed), D0(suppressed).
                   // The last two daughters are really one particle
 
  // check that the mother and all daughters are scalars:
  checkSpinParent( EvtSpinType::SCALAR );
  checkSpinDaughter( 0, EvtSpinType::SCALAR );
  checkSpinDaughter( 1, EvtSpinType::SCALAR );
  checkSpinDaughter( 2, EvtSpinType::SCALAR );
 
  // Check that the B dtr types are K D D:
 
  // get the parameters:
  _r           = getArg( 0 );
  double phase = getArg( 1 );
  _exp         = EvtComplex( cos( phase ), sin( phase ) );
}
 
//------------------------------------------------------------------
void EvtBtoKD3P::initProbMax() {
  setProbMax( 1 ); // this is later changed in decay()
}
 
//------------------------------------------------------------------
void EvtBtoKD3P::decay( EvtParticle* p ) {
  // tell the subclass that we decay the daughter:
  _daugsDecayedByParentModel = true;
 
  // the K is the 1st daughter of the B EvtParticle.
  // The decay mode of the allowed D (the one produced in b->c decay) is 2nd
  // The decay mode of the suppressed D (the one produced in b->u decay) is 3rd
  const int KIND  = 0;
  const int D1IND = 1;
  const int D2IND = 2;
 
  // generate kinematics of daughters (K and D):
  EvtId tempDaug[2] = { getDaug( KIND ), getDaug( D1IND ) };
  p->initializePhaseSpace( 2, tempDaug );
 
  // Get the D daughter particle and the decay models of the allowed
  // and suppressed D modes:
  EvtParticle* theD   = p->getDaug( D1IND );
  EvtPto3P*    model1 = (EvtPto3P*)( EvtDecayTable::getDecayFunc( theD ) );
 
  // for the suppressed mode, re-initialize theD as the suppressed D alias:
  theD->init( getDaug( D2IND ), theD->getP4() );
  EvtPto3P* model2 = (EvtPto3P*)( EvtDecayTable::getDecayFunc( theD ) );
 
  // on the first call:
  if ( false == _decayedOnce )
  {
    _decayedOnce = true;
 
    // store the D decay model pointers:
    _model1 = model1;
    _model2 = model2;
 
    // check the decay models of the first 2 daughters and that they
    // have the same final states:
    std::string name1;
    std::string name2;
    model1->getName( name1 );
    model2->getName( name2 );
 
    if ( name1 != "PTO3P" )
    {
      report( ERROR, "EvtGen" )
          << "D daughters of EvtBtoKD3P decay must decay via the \"PTO3P\" model" << endl
          << "    but found to decay via " << name1.c_str() << " or " << name2.c_str()
          << ". Will terminate execution!" << endl;
      assert( 0 );
    }
 
    EvtId* daugs1 = model1->getDaugs();
    EvtId* daugs2 = model2->getDaugs();
 
    bool idMatch = true;
    int  d;
    for ( d = 0; d < 2; ++d )
    {
      if ( daugs1[d] != daugs2[d] ) { idMatch = false; }
    }
    if ( false == idMatch )
    {
      report( ERROR, "EvtGen" )
          << "D daughters of EvtBtoKD3P decay must decay to the same final state" << endl
          << "   particles in the same order (not CP-conjugate order)," << endl
          << "   but they were found to decay to" << endl;
      for ( d = 0; d < model1->getNDaug(); ++d )
      { report( ERROR, "" ) << "   " << EvtPDL::name( daugs1[d] ).c_str() << " "; }
      report( ERROR, "" ) << endl;
      for ( d = 0; d < model1->getNDaug(); ++d )
      { report( ERROR, "" ) << "   " << EvtPDL::name( daugs2[d] ).c_str() << " "; }
      report( ERROR, "" ) << endl << ". Will terminate execution!" << endl;
      assert( 0 );
    }
 
    // estimate the probmax. Need to know the probmax's of the 2
    // models for this:
    setProbMax( model1->getProbMax( 0 ) + _r * _r * model2->getProbMax( 0 ) +
                2 * _r * sqrt( model1->getProbMax( 0 ) * model2->getProbMax( 0 ) ) );
 
  } // end of things to do on the first call
 
  // make sure the models haven't changed since the first call:
  if ( _model1 != model1 || _model2 != model2 )
  {
    report( ERROR, "EvtGen" )
        << "D daughters of EvtBtoKD3P decay should have only 1 decay modes, " << endl
        << "    but a new decay mode was found after the first call" << endl
        << "    Will terminate execution!" << endl;
    assert( 0 );
  }
 
  // get the cover function for each of the models and add them up.
  // They are summed with coefficients 1 because we are willing to
  // take a small inefficiency (~50%) in order to ensure that the
  // cover function is large enough without getting into complications
  // associated with the smallness of _r:
  EvtPdfSum<EvtDalitzPoint>* pc1 = model1->getPC();
  EvtPdfSum<EvtDalitzPoint>* pc2 = model2->getPC();
  EvtPdfSum<EvtDalitzPoint>  pc;
  pc.addTerm( 1.0, *pc1 );
  pc.addTerm( 1.0, *pc2 );
 
  // from this combined cover function, generate the Dalitz point:
  EvtDalitzPoint x = pc.randomPoint();
 
  // get the aptitude for each of the models on this point and add them up:
  EvtComplex amp1 = model1->amplNonCP( x );
  EvtComplex amp2 = model2->amplNonCP( x );
  EvtComplex amp  = amp1 + amp2 * _r * _exp;
 
  // get the value of the cover function for this point and set the
  // relative amplitude for this decay:
 
  double comp = sqrt( pc.evaluate( x ) );
  vertex( amp / comp );
 
  // Make the daughters of theD:
  theD->generateMassTree();
 
  // Now generate the p4's of the daughters of theD:
  std::vector<EvtVector4R> v = model2->initDaughters( x );
 
  if ( v.size() != theD->getNDaug() )
  {
    report( ERROR, "EvtGen" ) << "Number of daughters " << theD->getNDaug() << " != "
                              << "Momentum vector size " << v.size() << endl
                              << "     Terminating execution." << endl;
    assert( 0 );
  }
 
  // Apply the new p4's to the daughters:
  int i;
  for ( i = 0; i < theD->getNDaug(); ++i )
  { theD->getDaug( i )->init( model2->getDaugs()[i], v[i] ); }
}