BesEvtGen-00-04-08/src/EvtGen/EvtGenBase/EvtTwoBodyVertex.cc

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#include "EvtGenBase/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, [email protected], 2001-2002
 *
 * Copyright (C) 2002 Caltech
 *******************************************************************************/
 
#include <iostream>
#include <math.h>
#include <assert.h>
#include "EvtGenBase/EvtMacros.hh"
#include "EvtGenBase/EvtTwoBodyVertex.hh"
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;
}