EvtTwoBodyVertex.cc

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#include "EvtPatches.hh"
/*******************************************************************************
 * Project: BaBar detector at the SLAC PEP-II B-factory
 * Package: EvtGenBase
 *    File: $Id: EvtTwoBodyVertex.cc,v 1.4 2018/12/05 07:37:32 pingrg Exp $
 *  Author: Alexei Dvoretskii, dvoretsk@slac.stanford.edu, 2001-2002
 *
 * Copyright (C) 2002 Caltech
 *******************************************************************************/
 
#include "EvtMacros.hh"
#include "EvtTwoBodyVertex.hh"
#include <assert.h>
#include <iostream>
#include <math.h>
using std::endl;
using std::ostream;
 
// Default ctor can sometimes be useful
 
EvtTwoBodyVertex::EvtTwoBodyVertex() : _LL( 0 ), _p0( 0 ), _f( 0 ) {}
 
EvtTwoBodyVertex::EvtTwoBodyVertex( double mA, double mB, double mAB, int L )
    : _kine(), _LL( L ), _p0( 0 ), _f( 0 ) {
  // Kinematics is initialized only if the decay is above threshold
 
  if ( mAB > mA + mB )
  {
 
    _kine = EvtTwoBodyKine( mA, mB, mAB );
    _p0   = _kine.p();
  }
}
 
EvtTwoBodyVertex::EvtTwoBodyVertex( const EvtTwoBodyVertex& other )
    : _kine( other._kine )
    , _LL( other._LL )
    , _p0( other._p0 )
    , _f( ( other._f ) ? new EvtBlattWeisskopf( *other._f ) : 0 ) {}
 
EvtTwoBodyVertex::~EvtTwoBodyVertex() {
  if ( _f ) delete _f;
}
 
void EvtTwoBodyVertex::set_f( double R ) {
  if ( _f ) delete _f;
  _f = new EvtBlattWeisskopf( _LL, R, _p0 );
}
 
double EvtTwoBodyVertex::widthFactor( EvtTwoBodyKine x ) const {
  assert( _p0 > 0. );
 
  double p1     = x.p();
  double ff     = formFactor( x );
  double factor = pow( p1 / _p0, 2 * _LL + 1 ) * pow( mAB() / x.mAB(), 2 ) * ff *
                  ff; // pingrg,2008-11-24, in EvtGen Manual Eq 66, (m0/m) should be squared
  // see PLB537,201; PLB561, 55; ZPC48, 445, and PRD65, 032002, PRD68, 052006
  return factor;
}
 
double EvtTwoBodyVertex::phaseSpaceFactor( EvtTwoBodyKine x, EvtTwoBodyKine::Index i ) const {
  double p1     = x.p( i );
  double factor = pow( p1, _LL );
  return factor;
}
 
double EvtTwoBodyVertex::formFactor( EvtTwoBodyKine x ) const {
  double ff = 1.;
 
  if ( _f )
  {
 
    double p1 = x.p();
    ff        = ( *_f )( p1 );
  }
 
  return ff;
}
 
void EvtTwoBodyVertex::print( ostream& os ) const {
  os << " mA = " << mA() << endl;
  os << " mB = " << mB() << endl;
  os << "mAB = " << mAB() << endl;
  os << "  L = " << _LL << endl;
  os << " p0 = " << _p0 << endl;
}
 
ostream& operator<<( ostream& os, const EvtTwoBodyVertex& v ) {
  v.print( os );
  return os;
}