EvtVVS.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of models developed at BES collaboration
//      based on the EvtGen framework.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/BesCopyright
//      Copyright (A) 2006      Ping Rong-Gang @IHEP
//
// Module: VVS.hh
//
// Description: To define the helicity for vector(s=+1,-1)->vector(s=-1,0,1)+Pseudoscalar
//
// Modification history:
//
//    Ping R.-G.       Apr., 2006       Module created
//
//------------------------------------------------------------------------
//
#include "../EvtGenBase/EvtKine.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include <math.h>
#include <stdlib.h>
 
#include "../EvtGenBase/EvtHelSys.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include "../EvtGenBase/EvtVector4R.hh"
#include "EvtVVS.hh"
#include <string>
using namespace std;
 
double VVS::R00( double r ) { return r; }
 
double VVS::Fij( int i, int j, double r ) {
  double mpsi = ( _pd[0] + _pd[1] + _pd[2] ).mass();
  double temp = mpsi * r;
  if ( i == 0 && j == 0 ) return 0;
  if ( i == 1 && j == 0 ) return temp;
  if ( i == -1 && j == 0 ) return -temp;
  std::cerr << __FILE__ << ":" << __LINE__ << ": should not reach here" << std::endl;
  exit( 1 );
}
 
EvtComplex VVS::amps1( int m, int i, int j ) {
  double      mrho = _res[0];
  double      wrho = _res[1];
  double      s;
  EvtComplex  img( 0.0, 1.0 ), dpro;
  EvtVector4R prho;
  prho = _pd[i] + _pd[j];
  s    = prho.mass2();
  dpro = s - mrho * mrho + img * sqrt( s ) * wrho;
  EvtHelSys angles( prho, _pd[i] ), labAngles;
  double    theta, phi, ct1, st1, phi1, st, ct;
  double    rpp = angles.getHelAng( 0 );
  theta         = angles.getHelAng( 1 );
  phi           = angles.getHelAng( 2 );
  ct1           = labAngles.Angles( prho, 1 );
  phi1          = labAngles.Angles( prho, 2 );
  int        lamb;
  EvtComplex temp( 0.0, 0.0 );
  for ( lamb = -1; lamb <= 1; lamb++ )
    temp = temp + Fij( lamb, 0, prho.d3mag() ) * Djmn( 1, m, lamb, phi1, ct1, 0.0 ) / dpro *
                      R00( rpp ) * Djmn( 1, lamb, 0, phi, theta, 0.0 );
  return temp;
}
 
double VVS::amps() {
  double r1     = _par[0];
  double phase1 = _par[1];
  double r2     = _par[2];
  double phase2 = _par[3];
  double temp   = 0.0;
  int    m;
  for ( m = -1; m <= 1; m += 2 )
    temp = temp + pow( abs( r1 * exp( EvtComplex( 0, phase1 ) ) * amps1( m, 0, 1 ) +
                            r2 * exp( EvtComplex( 0, phase2 ) ) * amps1( m, 0, 2 ) +
                            amps1( m, 1, 2 ) ),
                       2. );
  return temp;
}