EvtFlatte.cc

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//--------------------------------------------------------------------------
//
// 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: See EvtGen/COPYRIGHT
//      Copyright (C) 1998      Caltech, UCSB
//
// Module: EvtFlatte.cc
//
// Description: resonance-defining class
//
// Modification history:
//
//    ponyisi  18 Feb 2008  created
//
//------------------------------------------------------------------------
//
#include "EvtFlatte.hh"
#include "EvtComplex.hh"
#include "EvtConst.hh"
#include "EvtKine.hh"
#include "EvtPatches.hh"
#include "EvtReport.hh"
#include "EvtVector4R.hh"
#include <math.h>
 
EvtFlatte::~EvtFlatte() {}
 
// operator
 
EvtFlatte& EvtFlatte::operator=( const EvtFlatte& n ) {
  if ( &n == this ) return *this;
  _p4_p   = n._p4_p;
  _p4_d1  = n._p4_d1;
  _p4_d2  = n._p4_d2;
  _ampl   = n._ampl;
  _theta  = n._theta;
  _mass   = n._mass;
  _params = n._params;
  //  _m1a = n._m1a;
  //  _m1b = n._m1b;
  //  _g1 = n._g1;
  //  _m2a = n._m2a;
  //  _m2b = n._m2b;
  //  _g2 = n._g2;
  return *this;
}
 
// constructor
 
EvtFlatte::EvtFlatte( const EvtVector4R& p4_p, const EvtVector4R& p4_d1,
                      const EvtVector4R& p4_d2, double ampl, double theta, double mass,
                      vector<EvtFlatteParam>& params
                      //                   double m1a, double m1b, double g1,
                      //                   double m2a, double m2b, double g2
                      )
    : _p4_p( p4_p )
    , _p4_d1( p4_d1 )
    , _p4_d2( p4_d2 )
    , _ampl( ampl )
    , _theta( theta )
    , _mass( mass )
    , _params( params )
//  _m1a(m1a), _m1b(m1b), _g1(g1),
//  _m2a(m2a), _m2b(m2b), _g2(g2)
{}
 
// amplitude function
 
EvtComplex EvtFlatte::resAmpl() {
 
  double pi180inv = 1.0 / EvtConst::radToDegrees;
 
  //   EvtComplex ampl(cos(_theta*pi180inv), sin(_theta*pi180inv));
  //   ampl *= _ampl;
 
  // SCALARS ONLY
  double mR = ( _p4_d1 + _p4_d2 ).mass();
 
  EvtComplex w;
 
  for ( vector<EvtFlatteParam>::const_iterator param = _params.begin(); param != _params.end();
        ++param )
  {
 
    double m1 = ( *param ).m1();
    double m2 = ( *param ).m2();
    double g  = ( *param ).g();
    w += ( g * g *
           sqrtCplx( ( 1 - ( ( m1 - m2 ) * ( m1 - m2 ) ) / ( mR * mR ) ) *
                     ( 1 - ( ( m1 + m2 ) * ( m1 + m2 ) ) / ( mR * mR ) ) ) );
    //     cout << m1 << " " << mR << " " << w << endl;
  }
 
  EvtComplex denom = _mass * _mass - mR * mR - EvtComplex( 0, 1 ) * w;
  EvtComplex ampl =
      _ampl * EvtComplex( cos( _theta * pi180inv ), sin( _theta * pi180inv ) ) / denom;
  //  cout << abs(1/denom) << endl;
  return ampl;
}