EvtPto3P.cc

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//-----------------------------------------------------------------------
// File and Version Information:
//      $Id: EvtPto3P.cc,v 1.1.1.2 2007/10/26 05:03:14 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) 1998 Caltech, UCSB
//
// Module creator:
//      Alexei Dvoretskii, Caltech, 2001-2002.
//-----------------------------------------------------------------------
#include "../EvtGenBase/EvtPatches.hh"
 
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtPto3PAmpFactory.hh"
#include "EvtPto3P.hh"
using namespace EvtCyclic3;
 
EvtDalitzPlot EvtPto3P::dp() {
  // There must be 3 daughters. All particles must be pseudoscalars.
  // Charge must be conserved. Number of arguments must be non-zero.
 
  EvtId parent = getParentId();
  assert( getNDaug() == 3 );
  EvtId dau0 = getDaug( 0 );
  EvtId dau1 = getDaug( 1 );
  EvtId dau2 = getDaug( 2 );
 
  assert( EvtPDL::getSpinType( parent ) == EvtSpinType::SCALAR );
  assert( EvtPDL::getSpinType( dau0 ) == EvtSpinType::SCALAR );
  assert( EvtPDL::getSpinType( dau1 ) == EvtSpinType::SCALAR );
  assert( EvtPDL::getSpinType( dau2 ) == EvtSpinType::SCALAR );
  assert( EvtPDL::chg3( parent ) ==
          EvtPDL::chg3( dau0 ) + EvtPDL::chg3( dau1 ) + EvtPDL::chg3( dau2 ) );
  assert( getNArg() > 0 );
 
  return EvtDalitzPlot( EvtPDL::getMass( dau0 ), EvtPDL::getMass( dau1 ),
                        EvtPDL::getMass( dau2 ), EvtPDL::getMass( parent ) );
}
 
EvtAmpFactory<EvtDalitzPoint>* EvtPto3P::createFactory( const EvtMultiChannelParser& parser ) {
  // Compute the interval size
 
  EvtDalitzPlot                  plot = dp();
  EvtAmpFactory<EvtDalitzPoint>* fact = new EvtPto3PAmpFactory( plot );
  fact->build( parser, 10000 );
  return fact;
}
 
std::vector<EvtVector4R> EvtPto3P::initDaughters( const EvtDalitzPoint& x ) const {
  std::vector<EvtVector4R> v;
  assert( x.isValid() );
 
  // Calculate in the r.f. of AB
 
  double eA  = x.e( A, AB );
  double eB  = x.e( B, AB );
  double eC  = x.e( C, AB );
  double pA  = x.p( A, AB );
  double pC  = x.p( C, AB );
  double cos = x.cosTh( CA, AB );
  double sin = sqrt( 1.0 - cos * cos );
 
  EvtVector4R vA( eA, 0, 0, pA );
  EvtVector4R vB( eB, 0, 0, -pA );
  EvtVector4R vC( eC, 0, pC * sin, pC * cos );
 
  // Boost from rest frame of AB to rest-frame of decaying particle
  // vboost is the 4-momentum of frame being boosted from in the frame
  // being boosted into.
 
  EvtVector4R vboost = vA + vB + vC;
  vboost.set( 1, -vboost.get( 1 ) );
  vboost.set( 2, -vboost.get( 2 ) );
  vboost.set( 3, -vboost.get( 3 ) );
  vA.applyBoostTo( vboost );
  vB.applyBoostTo( vboost );
  vC.applyBoostTo( vboost );
 
  // Rotate
 
  double alpha = EvtRandom::Flat( EvtConst::twoPi );
  double beta  = acos( EvtRandom::Flat( -1.0, 1.0 ) );
  double gamma = EvtRandom::Flat( EvtConst::twoPi );
 
  vA.applyRotateEuler( alpha, beta, gamma );
  vB.applyRotateEuler( alpha, beta, gamma );
  vC.applyRotateEuler( alpha, beta, gamma );
 
  // Fill vector
 
  assert( v.size() == 0 );
  v.push_back( vA );
  v.push_back( vB );
  v.push_back( vC );
 
  return v;
}