EvtSVVHelAmp.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: EvtSVVHelAmp.cc
//
// Description: Routine to decay scalar -> 2 vectors
//              by specifying the helicity amplitudes
//
// Modification history:
//
//    RYD       November 24, 1996       Module created
//
//------------------------------------------------------------------------
//
#include "EvtSVVHelAmp.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtId.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtTensor3C.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector3C.hh"
#include "../EvtGenBase/EvtVector3R.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <stdlib.h>
#include <string>
 
EvtSVVHelAmp::~EvtSVVHelAmp() {}
 
void EvtSVVHelAmp::getName( std::string& model_name ) { model_name = "SVV_HELAMP"; }
 
EvtDecayBase* EvtSVVHelAmp::clone() { return new EvtSVVHelAmp; }
 
void EvtSVVHelAmp::init() {
 
  // check that there are 6 arguments
  checkNArg( 6 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::SCALAR );
 
  checkSpinDaughter( 0, EvtSpinType::VECTOR );
  checkSpinDaughter( 1, EvtSpinType::VECTOR );
}
 
void EvtSVVHelAmp::initProbMax() {
 
  setProbMax( getArg( 0 ) * getArg( 0 ) + getArg( 2 ) * getArg( 2 ) +
              getArg( 4 ) * getArg( 4 ) );
}
 
void EvtSVVHelAmp::decay( EvtParticle* p ) {
 
  SVVHel( p, _amp2, getDaug( 0 ), getDaug( 1 ),
          EvtComplex( getArg( 0 ) * cos( getArg( 1 ) ), getArg( 0 ) * sin( getArg( 1 ) ) ),
          EvtComplex( getArg( 2 ) * cos( getArg( 3 ) ), getArg( 2 ) * sin( getArg( 3 ) ) ),
          EvtComplex( getArg( 4 ) * cos( getArg( 5 ) ), getArg( 4 ) * sin( getArg( 5 ) ) ) );
 
  return;
}
 
void EvtSVVHelAmp::SVVHel( EvtParticle* parent, EvtAmp& amp, EvtId n_v1, EvtId n_v2,
                           const EvtComplex& hp, const EvtComplex& h0, const EvtComplex& hm ) {
 
  //  Routine to decay a scalar into two vectors.  Started
  //  by ryd on Oct 17, 1996.
 
  int   tndaug = 2;
  EvtId tdaug[2];
  tdaug[0] = n_v1;
  tdaug[1] = n_v2;
 
  parent->initializePhaseSpace( tndaug, tdaug );
 
  EvtParticle *v1, *v2;
  v1 = parent->getDaug( 0 );
  v2 = parent->getDaug( 1 );
 
  EvtVector4R momv1 = v1->getP4();
  // EvtVector4R momv2 = v2->getP4();
 
  EvtVector3R v1dir( momv1.get( 1 ), momv1.get( 2 ), momv1.get( 3 ) );
  v1dir = v1dir / v1dir.d3mag();
 
  EvtComplex a = -0.5 * ( hp + hm );
  EvtComplex b = EvtComplex( 0.0, 0.5 ) * ( hp - hm );
  EvtComplex c = h0 + 0.5 * ( hp + hm );
 
  EvtTensor3C M = a * EvtTensor3C::id() + b * eps( v1dir ) + c * directProd( v1dir, v1dir );
 
  EvtVector3C t0 = M.cont1( v1->eps( 0 ).vec().conj() );
  EvtVector3C t1 = M.cont1( v1->eps( 1 ).vec().conj() );
  EvtVector3C t2 = M.cont1( v1->eps( 2 ).vec().conj() );
 
  EvtVector3C eps0 = v2->eps( 0 ).vec().conj();
  EvtVector3C eps1 = v2->eps( 1 ).vec().conj();
  EvtVector3C eps2 = v2->eps( 2 ).vec().conj();
 
  amp.vertex( 0, 0, t0 * eps0 );
  amp.vertex( 0, 1, t0 * eps1 );
  amp.vertex( 0, 2, t0 * eps2 );
 
  amp.vertex( 1, 0, t1 * eps0 );
  amp.vertex( 1, 1, t1 * eps1 );
  amp.vertex( 1, 2, t1 * eps2 );
 
  amp.vertex( 2, 0, t2 * eps0 );
  amp.vertex( 2, 1, t2 * eps1 );
  amp.vertex( 2, 2, t2 * eps2 );
 
  return;
}